Release 0.11.1.0

Name variablesInAllowedPositionRule's variables more meaningful.

CHANGELOG.md

@@ -6,6 +6,19 @@ The format is based on
 and this project adheres to
 [Haskell Package Versioning Policy](https://pvp.haskell.org/).
 
+## [0.11.1.0] - 2021-02-07
+### Added
+- `Validate.Rules`:
+  - `overlappingFieldsCanBeMergedRule`
+  - `possibleFragmentSpreadsRule`
+  - `variablesInAllowedPositionRule`
+  - `valuesOfCorrectTypeRule`
+- `Type.Schema.implementations` contains a map from interfaces and objects to
+  interfaces they implement.
+- Show instances for GraphQL type definitions in the `Type` modules.
+- Custom Show instances for type and value representations in the AST.
+- `AST.Document.escape` escapes a single character in a `StringValue`.
+
 ## [0.11.0.0] - 2020-11-07
 ### Changed
 - `AST.Document.Selection` wraps additional new types: `Field`, `FragmentSpread`
@@ -400,6 +413,7 @@ and this project adheres to
 ### Added
 - Data types for the GraphQL language.
 
+[0.11.1.0]: https://www.caraus.tech/projects/pub-graphql/repository/23/diff?rev=v0.11.1.0&rev_to=v0.11.0.0
 [0.11.0.0]: https://www.caraus.tech/projects/pub-graphql/repository/23/diff?rev=v0.11.0.0&rev_to=v0.10.0.0
 [0.10.0.0]: https://www.caraus.tech/projects/pub-graphql/repository/23/diff?rev=v0.10.0.0&rev_to=v0.9.0.0
 [0.9.0.0]: https://www.caraus.tech/projects/pub-graphql/repository/23/diff?rev=v0.9.0.0&rev_to=v0.8.0.0

README.md

@@ -3,29 +3,10 @@
 [![Simple Haskell](https://www.simplehaskell.org/badges/badge.svg)](https://www.simplehaskell.org)
 [![CI/CD](https://img.shields.io/badge/CI-CD-brightgreen)](https://build.caraus.tech/go/pipelines)
 
-This implementation is relatively low-level by design, it doesn't provide any
-mappings between the GraphQL types and Haskell's type system and avoids
-compile-time magic. It focuses on flexibility instead, so other solutions can
-be built on top of it.
+See https://www.caraus.tech/projects/pub-graphql.
 
-## State of the work
-
-For now this library provides:
-
-- Parser for the query and schema languages, as well as a printer for the query
-  language (minimizer and pretty-printer).
-- Data structures to define a type system.
-- Executor (queries, mutations and subscriptions are supported).
-- Validation is work in progress.
-- Introspection isn't available yet.
-
-But the idea is to be a Haskell port of
-[`graphql-js`](https://github.com/graphql/graphql-js).
-
-For a more precise list of currently missing features see
-[issues](https://www.caraus.tech/projects/pub-graphql/issues).
-
-## Documentation
+Report issues on the
+[bug tracker](https://www.caraus.tech/projects/pub-graphql/issues).
 
 API documentation is available through
 [Hackage](https://hackage.haskell.org/package/graphql).

graphql.cabal

@@ -4,10 +4,10 @@ cabal-version: 2.2
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: c89b0164372b6e02e4f338d3865dd6bb9dfd1a4475f25d808450480d73f94f91
+-- hash: 15a0880180192f918ba0bd3b3e955c57232f1efe8993745d505fcb6e1aab1451
 
 name:           graphql
-version:        0.11.0.0
+version:        0.11.1.0
 synopsis:       Haskell GraphQL implementation
 description:    Haskell <https://spec.graphql.org/June2018/ GraphQL> implementation.
 category:       Language
@@ -17,7 +17,7 @@ author:         Danny Navarro <j@dannynavarro.net>,
                 Matthías Páll Gissurarson <mpg@mpg.is>,
                 Sólrún Halla Einarsdóttir <she@mpg.is>
 maintainer:     belka@caraus.de
-copyright:      (c) 2019-2020 Eugen Wissner,
+copyright:      (c) 2019-2021 Eugen Wissner,
                 (c) 2015-2017 J. Daniel Navarro
 license:        MPL-2.0 AND BSD-3-Clause
 license-files:  LICENSE,
@@ -78,6 +78,7 @@ test-suite graphql-test
   type: exitcode-stdio-1.0
   main-is: Spec.hs
   other-modules:
+      Language.GraphQL.AST.DocumentSpec
       Language.GraphQL.AST.EncoderSpec
       Language.GraphQL.AST.LexerSpec
       Language.GraphQL.AST.ParserSpec
@@ -85,7 +86,7 @@ test-suite graphql-test
       Language.GraphQL.Execute.CoerceSpec
       Language.GraphQL.ExecuteSpec
       Language.GraphQL.Type.OutSpec
-      Language.GraphQL.ValidateSpec
+      Language.GraphQL.Validate.RulesSpec
       Test.DirectiveSpec
       Test.FragmentSpec
       Test.RootOperationSpec

package.yaml

@@ -1,5 +1,5 @@
 name: graphql
-version: 0.11.0.0
+version: 0.11.1.0
 synopsis: Haskell GraphQL implementation
 description:
   Haskell <https://spec.graphql.org/June2018/ GraphQL> implementation.
@@ -11,7 +11,7 @@ category: Language
 license: MPL-2.0 AND BSD-3-Clause
 
 copyright:
-- (c) 2019-2020 Eugen Wissner
+- (c) 2019-2021 Eugen Wissner
 - (c) 2015-2017 J. Daniel Navarro
 author:
 - Danny Navarro <j@dannynavarro.net>

src/Language/GraphQL/AST/Document.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE DuplicateRecordFields #-}
 {-# LANGUAGE ExplicitForAll #-}
+{-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE Safe #-}
@@ -47,11 +48,15 @@ module Language.GraphQL.AST.Document
     , UnionMemberTypes(..)
     , Value(..)
     , VariableDefinition(..)
+    , escape
     ) where
 
+import Data.Char (ord)
 import Data.Foldable (toList)
 import Data.Int (Int32)
+import Data.List (intercalate)
 import Data.List.NonEmpty (NonEmpty)
+import Numeric (showFloat, showHex)
 import Data.Text (Text)
 import qualified Data.Text as Text
 import Language.GraphQL.AST.DirectiveLocation (DirectiveLocation)
@@ -79,7 +84,10 @@ instance Ord Location where
 data Node a = Node
     { node :: a
     , location :: Location
-    } deriving (Eq, Show)
+    } deriving Eq
+
+instance Show a => Show (Node a) where
+    show Node{ node } = show node
 
 instance Functor Node where
     fmap f Node{..} = Node (f node) location
@@ -218,6 +226,28 @@ type TypeCondition = Name
 
 -- ** Input Values
 
+escape :: Char -> String
+escape char'
+    | char' == '\\' = "\\\\"
+    | char' == '\"' = "\\\""
+    | char' == '\b' = "\\b"
+    | char' == '\f' = "\\f"
+    | char' == '\n' = "\\n"
+    | char' == '\r' = "\\r"
+    | char' == '\t' = "\\t"
+    | char' < '\x0010' = unicode  "\\u000" char'
+    | char' < '\x0020' = unicode "\\u00" char'
+    | otherwise = [char']
+  where
+    unicode prefix uchar = prefix <> (showHex $ ord uchar) ""
+
+showList' :: Show a => [a] -> String
+showList' list = "[" ++ intercalate ", " (show <$> list) ++ "]"
+
+showObject :: Show a => [ObjectField a] -> String
+showObject fields =
+    "{ " ++ intercalate ", " (show <$> fields) ++ " }"
+
 -- | Input value (literal or variable).
 data Value
     = Variable Name
@@ -229,7 +259,19 @@ data Value
     | Enum Name
     | List [Value]
     | Object [ObjectField Value]
-    deriving (Eq, Show)
+    deriving Eq
+
+instance Show Value where
+    showList = mappend . showList'
+    show (Variable variableName) = '$' : Text.unpack variableName
+    show (Int integer) = show integer
+    show (Float float) = show $ ConstFloat float
+    show (String text) = show $  ConstString text
+    show (Boolean boolean) = show boolean
+    show Null = "null"
+    show (Enum name) = Text.unpack name
+    show (List list) = show list
+    show (Object fields) = showObject fields
 
 -- | Constant input value.
 data ConstValue
@@ -241,7 +283,18 @@ data ConstValue
     | ConstEnum Name
     | ConstList [ConstValue]
     | ConstObject [ObjectField ConstValue]
-    deriving (Eq, Show)
+    deriving Eq
+
+instance Show ConstValue where
+    showList = mappend . showList'
+    show (ConstInt integer) = show integer
+    show (ConstFloat float) = showFloat float mempty
+    show (ConstString text) = "\"" <> Text.foldr (mappend . escape) "\"" text
+    show (ConstBoolean boolean) = show boolean
+    show ConstNull = "null"
+    show (ConstEnum name) = Text.unpack name
+    show (ConstList list) = show list
+    show (ConstObject fields) = showObject fields
 
 -- | Key-value pair.
 --
@@ -250,7 +303,13 @@ data ObjectField a = ObjectField
     { name :: Name
     , value :: Node a
     , location :: Location
-    } deriving (Eq, Show)
+    } deriving Eq
+
+instance Show a => Show (ObjectField a) where
+    show ObjectField{..} = Text.unpack name ++ ": " ++ show value
+
+instance Functor ObjectField where
+    fmap f ObjectField{..} = ObjectField name (f <$> value) location
 
 -- ** Variables
 
@@ -281,7 +340,12 @@ data Type
     = TypeNamed Name
     | TypeList Type
     | TypeNonNull NonNullType
-    deriving (Eq, Show)
+    deriving Eq
+
+instance Show Type where
+    show (TypeNamed typeName) = Text.unpack typeName
+    show (TypeList listType) = concat ["[", show listType, "]"]
+    show (TypeNonNull nonNullType) = show nonNullType
 
 -- | Represents type names.
 type NamedType = Name
@@ -290,7 +354,11 @@ type NamedType = Name
 data NonNullType
     = NonNullTypeNamed Name
     | NonNullTypeList Type
-    deriving (Eq, Show)
+    deriving Eq
+
+instance Show NonNullType where
+    show (NonNullTypeNamed typeName) = '!' : Text.unpack typeName
+    show (NonNullTypeList listType) =  concat ["![", show listType, "]"]
 
 -- ** Directives
 

src/Language/GraphQL/AST/Encoder.hs

@@ -16,7 +16,6 @@ module Language.GraphQL.AST.Encoder
     , value
     ) where
 
-import Data.Char (ord)
 import Data.Foldable (fold)
 import qualified Data.List.NonEmpty as NonEmpty
 import Data.Text (Text)
@@ -25,7 +24,7 @@ import qualified Data.Text.Lazy as Lazy (Text)
 import qualified Data.Text.Lazy as Lazy.Text
 import Data.Text.Lazy.Builder (Builder)
 import qualified Data.Text.Lazy.Builder as Builder
-import Data.Text.Lazy.Builder.Int (decimal, hexadecimal)
+import Data.Text.Lazy.Builder.Int (decimal)
 import Data.Text.Lazy.Builder.RealFloat (realFloat)
 import qualified Language.GraphQL.AST.Document as Full
 
@@ -234,11 +233,12 @@ quote :: Builder.Builder
 quote = Builder.singleton '\"'
 
 oneLine :: Text -> Builder
-oneLine string = quote <> Text.foldr (mappend . escape) quote string
+oneLine string = quote <> Text.foldr merge quote string
+  where
+    merge = mappend . Builder.fromString . Full.escape
 
 stringValue :: Formatter -> Text -> Lazy.Text
-stringValue Minified string = Builder.toLazyText
-    $ quote <> Text.foldr (mappend . escape) quote string
+stringValue Minified string = Builder.toLazyText $ oneLine string
 stringValue (Pretty indentation) string =
   if hasEscaped string
   then stringValue Minified string
@@ -266,21 +266,6 @@ stringValue (Pretty indentation) string =
             = Builder.fromLazyText (indent (indentation + 1))
             <> line' <> newline <> acc
 
-escape :: Char -> Builder
-escape char'
-    | char' == '\\' = Builder.fromString "\\\\"
-    | char' == '\"' = Builder.fromString "\\\""
-    | char' == '\b' = Builder.fromString "\\b"
-    | char' == '\f' = Builder.fromString "\\f"
-    | char' == '\n' = Builder.fromString "\\n"
-    | char' == '\r' = Builder.fromString "\\r"
-    | char' == '\t' = Builder.fromString "\\t"
-    | char' < '\x0010' = unicode  "\\u000" char'
-    | char' < '\x0020' = unicode "\\u00" char'
-    | otherwise = Builder.singleton char'
-  where
-    unicode prefix = mappend (Builder.fromString prefix) . (hexadecimal . ord)
-
 listValue :: Formatter -> [Full.Value] -> Lazy.Text
 listValue formatter = bracketsCommas formatter $ value formatter
 

src/Language/GraphQL/Type/Definition.hs

@@ -22,6 +22,7 @@ import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
 import Data.String (IsString(..))
 import Data.Text (Text)
+import qualified Data.Text as Text
 import Language.GraphQL.AST (Name)
 import Prelude hiding (id)
 
@@ -63,6 +64,9 @@ data ScalarType = ScalarType Name (Maybe Text)
 instance Eq ScalarType where
     (ScalarType this _) == (ScalarType that _) = this == that
 
+instance Show ScalarType where
+    show (ScalarType typeName _) = Text.unpack typeName
+
 -- | Enum type definition.
 --
 -- Some leaf values of requests and input values are Enums. GraphQL serializes
@@ -73,6 +77,9 @@ data EnumType = EnumType Name (Maybe Text) (HashMap Name EnumValue)
 instance Eq EnumType where
     (EnumType this _ _) == (EnumType that _ _) = this == that
 
+instance Show EnumType where
+    show (EnumType typeName _ _) = Text.unpack typeName
+
 -- | Enum value is a single member of an 'EnumType'.
 newtype EnumValue = EnumValue (Maybe Text)
 

src/Language/GraphQL/Type/In.hs

@@ -24,6 +24,7 @@ module Language.GraphQL.Type.In
 
 import Data.HashMap.Strict (HashMap)
 import Data.Text (Text)
+import qualified Data.Text as Text
 import Language.GraphQL.AST.Document (Name)
 import qualified Language.GraphQL.Type.Definition as Definition
 
@@ -40,6 +41,9 @@ data InputObjectType = InputObjectType
 instance Eq InputObjectType where
     (InputObjectType this _ _) == (InputObjectType that _ _) = this == that
 
+instance Show InputObjectType where
+    show (InputObjectType typeName _ _) = Text.unpack typeName
+
 -- | These types may be used as input types for arguments and directives.
 --
 -- GraphQL distinguishes between "wrapping" and "named" types. Each wrapping
@@ -56,6 +60,16 @@ data Type
     | NonNullListType Type
     deriving Eq
 
+instance Show Type where
+    show (NamedScalarType scalarType) = show scalarType
+    show (NamedEnumType enumType) = show enumType
+    show (NamedInputObjectType inputObjectType) = show inputObjectType
+    show (ListType baseType) = concat ["[", show baseType, "]"]
+    show (NonNullScalarType scalarType) = '!' : show scalarType
+    show (NonNullEnumType enumType) = '!' : show enumType
+    show (NonNullInputObjectType inputObjectType) = '!' : show inputObjectType
+    show (NonNullListType baseType) = concat ["![", show baseType, "]"]
+
 -- | Field argument definition.
 data Argument = Argument (Maybe Text) Type (Maybe Definition.Value)
 

src/Language/GraphQL/Type/Internal.hs

@@ -14,11 +14,14 @@ module Language.GraphQL.Type.Internal
     , Type(..)
     , directives
     , doesFragmentTypeApply
+    , implementations
     , instanceOf
+    , lookupCompositeField
     , lookupInputType
     , lookupTypeCondition
     , lookupTypeField
     , mutation
+    , outToComposite
     , subscription
     , query
     , types
@@ -62,26 +65,31 @@ data Schema m = Schema
     (Maybe (Out.ObjectType m))
     Directives
     (HashMap Full.Name (Type m))
+    (HashMap Full.Name [Type m])
 
 -- | Schema query type.
 query :: forall m. Schema m -> Out.ObjectType m
-query (Schema query' _ _ _ _) = query'
+query (Schema query' _ _ _ _ _) = query'
 
 -- | Schema mutation type.
 mutation :: forall m. Schema m -> Maybe (Out.ObjectType m)
-mutation (Schema _ mutation' _ _ _) = mutation'
+mutation (Schema _ mutation' _ _ _ _) = mutation'
 
 -- | Schema subscription type.
 subscription :: forall m. Schema m -> Maybe (Out.ObjectType m)
-subscription (Schema _ _ subscription' _ _) = subscription'
+subscription (Schema _ _ subscription' _ _ _) = subscription'
 
 -- | Schema directive definitions.
 directives :: forall m. Schema m -> Directives
-directives (Schema _ _ _ directives' _) = directives'
+directives (Schema _ _ _ directives' _ _) = directives'
 
 -- | Types referenced by the schema.
 types :: forall m. Schema m -> HashMap Full.Name (Type m)
-types (Schema _ _ _ _ types') = types'
+types (Schema _ _ _ _ types' _) = types'
+
+-- | Interface implementations.
+implementations :: forall m. Schema m -> HashMap Full.Name [Type m]
+implementations (Schema _ _ _ _ _ implementations') = implementations'
 
 -- | These types may describe the parent context of a selection set.
 data CompositeType m
@@ -160,12 +168,16 @@ lookupInputType (Full.TypeNonNull (Full.NonNullTypeList nonNull)) types'
     <$> lookupInputType nonNull types'
 
 lookupTypeField :: forall a. Full.Name -> Out.Type a -> Maybe (Out.Field a)
-lookupTypeField fieldName = \case
-    Out.ObjectBaseType objectType ->
-        objectChild objectType
-    Out.InterfaceBaseType interfaceType ->
-        interfaceChild interfaceType
-    Out.ListBaseType listType -> lookupTypeField fieldName listType
+lookupTypeField fieldName outputType =
+    outToComposite outputType >>= lookupCompositeField fieldName
+
+lookupCompositeField :: forall a
+    . Full.Name
+    -> CompositeType a
+    -> Maybe (Out.Field a)
+lookupCompositeField fieldName = \case
+    CompositeObjectType objectType -> objectChild objectType
+    CompositeInterfaceType interfaceType -> interfaceChild interfaceType
     _ -> Nothing
   where
     objectChild (Out.ObjectType _ _ _ resolvers) =
@@ -174,3 +186,12 @@ lookupTypeField fieldName = \case
         HashMap.lookup fieldName fields
     resolverType (Out.ValueResolver objectField _) = objectField
     resolverType (Out.EventStreamResolver objectField _ _) = objectField
+
+outToComposite :: forall a. Out.Type a -> Maybe (CompositeType a)
+outToComposite = \case
+    Out.ObjectBaseType objectType -> Just $ CompositeObjectType objectType
+    Out.InterfaceBaseType interfaceType ->
+        Just $ CompositeInterfaceType interfaceType
+    Out.UnionBaseType unionType -> Just $ CompositeUnionType unionType
+    Out.ListBaseType listType -> outToComposite listType
+    _ -> Nothing

src/Language/GraphQL/Type/Out.hs

@@ -38,6 +38,7 @@ import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
 import Data.Maybe (fromMaybe)
 import Data.Text (Text)
+import qualified Data.Text as Text
 import Language.GraphQL.AST (Name)
 import Language.GraphQL.Type.Definition
 import qualified Language.GraphQL.Type.In as In
@@ -52,6 +53,9 @@ data ObjectType m = ObjectType
 instance forall a. Eq (ObjectType a) where
     (ObjectType this _ _ _) == (ObjectType that _ _ _) = this == that
 
+instance forall a. Show (ObjectType a) where
+    show (ObjectType typeName _ _ _) = Text.unpack typeName
+
 -- | Interface Type Definition.
 --
 -- When a field can return one of a heterogeneous set of types, a Interface type
@@ -63,6 +67,9 @@ data InterfaceType m = InterfaceType
 instance forall a. Eq (InterfaceType a) where
     (InterfaceType this _ _ _) == (InterfaceType that _ _ _) = this == that
 
+instance forall a. Show (InterfaceType a) where
+    show (InterfaceType typeName _ _ _) = Text.unpack typeName
+
 -- | Union Type Definition.
 --
 -- When a field can return one of a heterogeneous set of types, a Union type is
@@ -72,6 +79,9 @@ data UnionType m = UnionType Name (Maybe Text) [ObjectType m]
 instance forall a. Eq (UnionType a) where
     (UnionType this _ _) == (UnionType that _ _) = this == that
 
+instance forall a. Show (UnionType a) where
+    show (UnionType typeName _ _) = Text.unpack typeName
+
 -- | Output object field definition.
 data Field m = Field
     (Maybe Text) -- ^ Description.
@@ -98,6 +108,20 @@ data Type m
     | NonNullListType (Type m)
     deriving Eq
 
+instance forall a. Show (Type a) where
+    show (NamedScalarType scalarType) = show scalarType
+    show (NamedEnumType enumType) = show enumType
+    show (NamedObjectType inputObjectType) = show inputObjectType
+    show (NamedInterfaceType interfaceType) = show interfaceType
+    show (NamedUnionType unionType) = show unionType
+    show (ListType baseType) = concat ["[", show baseType, "]"]
+    show (NonNullScalarType scalarType) = '!' : show scalarType
+    show (NonNullEnumType enumType) = '!' : show enumType
+    show (NonNullObjectType inputObjectType) = '!' : show inputObjectType
+    show (NonNullInterfaceType interfaceType) = '!' : show interfaceType
+    show (NonNullUnionType unionType) = '!' : show unionType
+    show (NonNullListType baseType) = concat ["![", show baseType, "]"]
+
 -- | Matches either 'NamedScalarType' or 'NonNullScalarType'.
 pattern ScalarBaseType :: forall m. ScalarType -> Type m
 pattern ScalarBaseType scalarType <- (isScalarType -> Just scalarType)

src/Language/GraphQL/Type/Schema.hs

@@ -23,6 +23,7 @@ import Language.GraphQL.Type.Internal
     , Schema
     , Type(..)
     , directives
+    , implementations
     , mutation
     , subscription
     , query
@@ -41,9 +42,11 @@ schema :: forall m
     -> Directives -- ^ Directive definitions.
     -> Schema m -- ^ Schema.
 schema queryRoot mutationRoot subscriptionRoot directiveDefinitions =
-    Internal.Schema queryRoot mutationRoot subscriptionRoot allDirectives collectedTypes
+    Internal.Schema queryRoot mutationRoot subscriptionRoot
+        allDirectives collectedTypes collectedImplementations
   where
     collectedTypes = collectReferencedTypes queryRoot mutationRoot subscriptionRoot
+    collectedImplementations = collectImplementations collectedTypes
     allDirectives = HashMap.union directiveDefinitions defaultDirectives
     defaultDirectives = HashMap.fromList
         [ ("skip", skipDirective)
@@ -153,3 +156,20 @@ collectReferencedTypes queryRoot mutationRoot subscriptionRoot =
     polymorphicTraverser interfaces fields
         = flip (foldr visitFields) fields
         . flip (foldr traverseInterfaceType) interfaces
+
+-- | Looks for objects and interfaces under the schema types and collects the
+-- interfaces they implement.
+collectImplementations :: forall m
+    . HashMap Full.Name (Type m)
+    -> HashMap Full.Name [Type m]
+collectImplementations = HashMap.foldr go HashMap.empty
+  where
+    go implementation@(InterfaceType interfaceType) accumulator =
+        let Out.InterfaceType _ _ interfaces _ = interfaceType
+         in foldr (add implementation) accumulator interfaces
+    go implementation@(ObjectType objectType) accumulator =
+        let Out.ObjectType _ _ interfaces _ = objectType
+         in foldr (add implementation) accumulator interfaces
+    go _ accumulator = accumulator
+    add implementation (Out.InterfaceType typeName _ _ _) accumulator =
+        HashMap.insertWith (++) typeName [implementation] accumulator

src/Language/GraphQL/Validate.hs

@@ -210,7 +210,7 @@ typeDefinition context rule = \case
         directives context rule scalarLocation directives'
     Full.ObjectTypeDefinition _ _ _ directives' fields
         -> directives context rule objectLocation directives'
-         >< foldMap (fieldDefinition context rule) fields
+        >< foldMap (fieldDefinition context rule) fields
     Full.InterfaceTypeDefinition _ _ directives' fields
         -> directives context rule interfaceLocation directives'
         >< foldMap (fieldDefinition context rule) fields

src/Language/GraphQL/Validate/Rules.hs

@@ -3,6 +3,7 @@
    obtain one at https://mozilla.org/MPL/2.0/. -}
 
 {-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -24,6 +25,8 @@ module Language.GraphQL.Validate.Rules
     , noUndefinedVariablesRule
     , noUnusedFragmentsRule
     , noUnusedVariablesRule
+    , overlappingFieldsCanBeMergedRule
+    , possibleFragmentSpreadsRule
     , providedRequiredInputFieldsRule
     , providedRequiredArgumentsRule
     , scalarLeafsRule
@@ -35,22 +38,24 @@ module Language.GraphQL.Validate.Rules
     , uniqueInputFieldNamesRule
     , uniqueOperationNamesRule
     , uniqueVariableNamesRule
+    , valuesOfCorrectTypeRule
+    , variablesInAllowedPositionRule
     , variablesAreInputTypesRule
     ) where
 
 import Control.Monad ((>=>), foldM)
 import Control.Monad.Trans.Class (MonadTrans(..))
-import Control.Monad.Trans.Reader (ReaderT(..), asks, mapReaderT)
+import Control.Monad.Trans.Reader (ReaderT(..), ask, asks, mapReaderT)
 import Control.Monad.Trans.State (StateT, evalStateT, gets, modify)
 import Data.Bifunctor (first)
-import Data.Foldable (find, toList)
+import Data.Foldable (find, fold, foldl', toList)
 import qualified Data.HashMap.Strict as HashMap
 import Data.HashMap.Strict (HashMap)
 import Data.HashSet (HashSet)
 import qualified Data.HashSet as HashSet
 import Data.List (groupBy, sortBy, sortOn)
-import Data.Maybe (isNothing, mapMaybe)
-import Data.List.NonEmpty (NonEmpty)
+import Data.Maybe (catMaybes, fromMaybe, isJust, isNothing, mapMaybe)
+import Data.List.NonEmpty (NonEmpty(..))
 import Data.Ord (comparing)
 import Data.Sequence (Seq(..), (|>))
 import qualified Data.Sequence as Seq
@@ -80,6 +85,7 @@ specifiedRules =
     -- Fields
     , fieldsOnCorrectTypeRule
     , scalarLeafsRule
+    , overlappingFieldsCanBeMergedRule
     -- Arguments.
     , knownArgumentNamesRule
     , uniqueArgumentNamesRule
@@ -91,7 +97,9 @@ specifiedRules =
     , noUnusedFragmentsRule
     , fragmentSpreadTargetDefinedRule
     , noFragmentCyclesRule
+    , possibleFragmentSpreadsRule
     -- Values
+    , valuesOfCorrectTypeRule
     , knownInputFieldNamesRule
     , uniqueInputFieldNamesRule
     , providedRequiredInputFieldsRule
@@ -104,6 +112,7 @@ specifiedRules =
     , variablesAreInputTypesRule
     , noUndefinedVariablesRule
     , noUnusedVariablesRule
+    , variablesInAllowedPositionRule
     ]
 
 -- | Definition must be OperationDefinition or FragmentDefinition.
@@ -320,10 +329,8 @@ fragmentSpreadTypeExistenceRule :: forall m. Rule m
 fragmentSpreadTypeExistenceRule = SelectionRule $ const $ \case
     Full.FragmentSpreadSelection fragmentSelection
         | Full.FragmentSpread fragmentName _ location' <- fragmentSelection -> do
-            ast' <- asks ast
-            let target = find (isSpreadTarget fragmentName) ast'
-            typeCondition <- lift $ maybeToSeq $ target >>= extractTypeCondition
             types' <- asks $ Schema.types . schema
+            typeCondition <- findSpreadTarget fragmentName
             case HashMap.lookup typeCondition types' of
                 Nothing -> pure $ Error
                     { message = spreadError fragmentName typeCondition
@@ -342,10 +349,6 @@ fragmentSpreadTypeExistenceRule = SelectionRule $ const $ \case
                 Just _ -> lift mempty
     _ -> lift mempty
   where
-    extractTypeCondition (viewFragment -> Just fragmentDefinition) =
-        let Full.FragmentDefinition _ typeCondition _ _ _ = fragmentDefinition
-         in Just typeCondition
-    extractTypeCondition _ = Nothing
     spreadError fragmentName typeCondition = concat
         [ "Fragment \""
         , Text.unpack fragmentName
@@ -451,8 +454,7 @@ filterSelections applyFilter selections
 noFragmentCyclesRule :: forall m. Rule m
 noFragmentCyclesRule = FragmentDefinitionRule $ \case
     Full.FragmentDefinition fragmentName _ _ selections location' -> do
-        state <- evalStateT (collectFields selections)
-            (0, fragmentName)
+        state <- evalStateT (collectCycles selections) (0, fragmentName)
         let spreadPath = fst <$> sortBy (comparing snd) (HashMap.toList state)
         case reverse spreadPath of
             x : _ | x == fragmentName -> pure $ Error
@@ -467,10 +469,10 @@ noFragmentCyclesRule = FragmentDefinitionRule $ \case
                 }
             _ -> lift mempty
   where
-    collectFields :: Traversable t
+    collectCycles :: Traversable t
         => t Full.Selection
         -> StateT (Int, Full.Name) (ReaderT (Validation m) Seq) (HashMap Full.Name Int)
-    collectFields selectionSet = foldM forEach HashMap.empty selectionSet
+    collectCycles selectionSet = foldM forEach HashMap.empty selectionSet
     forEach accumulator = \case
         Full.FieldSelection fieldSelection -> forField accumulator fieldSelection
         Full.InlineFragmentSelection fragmentSelection ->
@@ -487,15 +489,15 @@ noFragmentCyclesRule = FragmentDefinitionRule $ \case
             then pure newAccumulator
             else collectFromSpread fragmentName newAccumulator
     forInline accumulator (Full.InlineFragment _ _ selections _) =
-        (accumulator <>) <$> collectFields selections
+        (accumulator <>) <$> collectCycles selections
     forField accumulator (Full.Field _ _ _ _ selections _) =
-        (accumulator <>) <$> collectFields selections
+        (accumulator <>) <$> collectCycles selections
     collectFromSpread fragmentName accumulator = do
         ast' <- lift $ asks ast
         case findFragmentDefinition fragmentName ast' of
             Nothing -> pure accumulator
             Just (Full.FragmentDefinition _ _ _ selections _) ->
-                (accumulator <>) <$> collectFields selections
+                (accumulator <>) <$> collectCycles selections
 
 findFragmentDefinition :: Text
     -> NonEmpty Full.Definition
@@ -531,15 +533,22 @@ uniqueDirectiveNamesRule = DirectivesRule
     extract (Full.Directive directiveName _ location') =
         (directiveName, location')
 
-filterDuplicates :: (a -> (Text, Full.Location)) -> String -> [a] -> Seq Error
+groupSorted :: forall a. (a -> Text) -> [a] -> [[a]]
+groupSorted getName = groupBy equalByName . sortOn getName
+  where
+    equalByName lhs rhs = getName lhs == getName rhs
+
+filterDuplicates :: forall a
+    . (a -> (Text, Full.Location))
+    -> String
+    -> [a]
+    -> Seq Error
 filterDuplicates extract nodeType = Seq.fromList
     . fmap makeError
     . filter ((> 1) . length)
-    . groupBy equalByName
-    . sortOn getName
+    . groupSorted getName
   where
     getName = fst . extract
-    equalByName lhs rhs = getName lhs == getName rhs
     makeError directives' = Error
         { message = makeMessage $ head directives'
         , locations = snd . extract <$> directives'
@@ -647,12 +656,9 @@ variableUsageDifference difference errorMessage = OperationDefinitionRule $ \cas
             lift $ lift $ mapArguments arguments <> mapDirectives directives'
     variableFilter (Full.FragmentSpreadSelection spread)
         | Full.FragmentSpread fragmentName _ _ <- spread = do
-            definitions <- lift $ asks ast
-            visited <- gets (HashSet.member fragmentName)
-            modify (HashSet.insert fragmentName)
-            case find (isSpreadTarget fragmentName) definitions of
-                Just (viewFragment -> Just fragmentDefinition)
-                    | not visited -> diveIntoSpread fragmentDefinition
+            nonVisitedFragmentDefinition <- visitFragmentDefinition fragmentName
+            case nonVisitedFragmentDefinition of
+                Just fragmentDefinition -> diveIntoSpread fragmentDefinition
                 _ -> lift $ lift mempty
     diveIntoSpread (Full.FragmentDefinition _ _ directives' selections _)
         = filterSelections' selections
@@ -710,7 +716,7 @@ fieldsOnCorrectTypeRule = FieldRule fieldRule
     fieldRule parentType (Full.Field _ fieldName _ _ _ location')
         | Just objectType <- parentType
         , Nothing <- Type.lookupTypeField fieldName objectType
-        , Just typeName <- compositeTypeName objectType = pure $ Error
+        , Just typeName <- typeNameIfComposite objectType = pure $ Error
             { message = errorMessage fieldName typeName
             , locations = [location']
             }
@@ -723,20 +729,17 @@ fieldsOnCorrectTypeRule = FieldRule fieldRule
         , "\"."
         ]
 
-compositeTypeName :: forall m. Out.Type m -> Maybe Full.Name
-compositeTypeName (Out.ObjectBaseType (Out.ObjectType typeName _ _ _)) =
-    Just typeName
-compositeTypeName (Out.InterfaceBaseType interfaceType) =
+compositeTypeName :: forall m. Type.CompositeType m -> Full.Name
+compositeTypeName (Type.CompositeObjectType (Out.ObjectType typeName _ _ _)) =
+    typeName
+compositeTypeName (Type.CompositeInterfaceType interfaceType) =
     let Out.InterfaceType typeName _ _ _ = interfaceType
-        in Just typeName
-compositeTypeName (Out.UnionBaseType (Out.UnionType typeName _ _)) =
-    Just typeName
-compositeTypeName (Out.ScalarBaseType _) =
-    Nothing
-compositeTypeName (Out.EnumBaseType _) =
-    Nothing
-compositeTypeName (Out.ListBaseType wrappedType) =
-    compositeTypeName wrappedType
+     in typeName
+compositeTypeName (Type.CompositeUnionType (Out.UnionType typeName _ _)) =
+    typeName
+
+typeNameIfComposite :: forall m. Out.Type m -> Maybe Full.Name
+typeNameIfComposite = fmap compositeTypeName . Type.outToComposite
 
 -- | Field selections on scalars or enums are never allowed, because they are
 -- the leaf nodes of any GraphQL query.
@@ -794,7 +797,7 @@ knownArgumentNamesRule = ArgumentsRule fieldRule directiveRule
   where
     fieldRule (Just objectType) (Full.Field _ fieldName arguments  _ _ _)
         | Just typeField <- Type.lookupTypeField fieldName objectType
-        , Just typeName <- compositeTypeName objectType =
+        , Just typeName <- typeNameIfComposite objectType =
             lift $ foldr (go typeName fieldName typeField) Seq.empty arguments
     fieldRule _ _ = lift mempty
     go typeName fieldName fieldDefinition (Full.Argument argumentName _ location') errors
@@ -1013,3 +1016,590 @@ providedRequiredInputFieldsRule = ValueRule go constGo
         , Text.unpack typeName
         , "\" is required, but it was not provided."
         ]
+
+-- | If multiple field selections with the same response names are encountered
+-- during execution, the field and arguments to execute and the resulting value
+-- should be unambiguous. Therefore any two field selections which might both be
+-- encountered for the same object are only valid if they are equivalent.
+--
+-- For simple hand‐written GraphQL, this rule is obviously a clear developer
+-- error, however nested fragments can make this difficult to detect manually.
+overlappingFieldsCanBeMergedRule :: Rule m
+overlappingFieldsCanBeMergedRule = OperationDefinitionRule $ \case
+    Full.SelectionSet selectionSet _ -> do
+        schema' <- asks schema
+        go (toList selectionSet)
+            $ Type.CompositeObjectType
+            $ Schema.query schema'
+    Full.OperationDefinition operationType _ _ _ selectionSet _ -> do
+        schema' <- asks schema
+        let root = go (toList selectionSet) . Type.CompositeObjectType
+        case operationType of
+            Full.Query -> root $ Schema.query schema'
+            Full.Mutation
+                | Just objectType <- Schema.mutation schema' -> root objectType
+            Full.Subscription
+                | Just objectType <- Schema.mutation schema' -> root objectType
+            _ -> lift mempty
+  where
+    go selectionSet selectionType = do
+        fieldTuples <- evalStateT (collectFields selectionType selectionSet) HashSet.empty
+        fieldsInSetCanMerge fieldTuples
+    fieldsInSetCanMerge :: forall m
+        . HashMap Full.Name (NonEmpty (Full.Field, Type.CompositeType m))
+        -> ReaderT (Validation m) Seq Error
+    fieldsInSetCanMerge fieldTuples = do
+        validation <- ask
+        let (lonely, paired) = flattenPairs fieldTuples
+        let reader = flip runReaderT validation
+        lift $ foldMap (reader . visitLonelyFields) lonely
+            <> foldMap (reader . forEachFieldTuple) paired
+    forEachFieldTuple :: forall m
+        . (FieldInfo m, FieldInfo m)
+        -> ReaderT (Validation m) Seq Error
+    forEachFieldTuple (fieldA, fieldB) =
+        case (parent fieldA, parent fieldB) of
+            (parentA@Type.CompositeObjectType{}, parentB@Type.CompositeObjectType{})
+                | parentA /= parentB -> sameResponseShape fieldA fieldB
+            _ -> mapReaderT (checkEquality (node fieldA) (node fieldB))
+                $ sameResponseShape fieldA fieldB
+    checkEquality fieldA fieldB Seq.Empty
+        | Full.Field _ fieldNameA _ _ _ _ <- fieldA
+        , Full.Field _ fieldNameB _ _ _ _ <- fieldB
+        , fieldNameA /= fieldNameB = pure $ makeError fieldA fieldB
+        | Full.Field _ fieldNameA argumentsA _ _ locationA <- fieldA
+        , Full.Field _ _ argumentsB _ _ locationB <- fieldB
+        , argumentsA /= argumentsB =
+            let message = concat
+                    [ "Fields \""
+                    , Text.unpack fieldNameA
+                    , "\" conflict because they have different arguments. Use "
+                    , "different aliases on the fields to fetch both if this "
+                    , "was intentional."
+                    ]
+             in pure $ Error message [locationB, locationA]
+    checkEquality _ _ previousErrors = previousErrors
+    visitLonelyFields FieldInfo{..} =
+        let Full.Field _ _ _ _ subSelections _ = node
+            compositeFieldType = Type.outToComposite type'
+         in maybe (lift Seq.empty) (go subSelections) compositeFieldType
+    sameResponseShape :: forall m
+        . FieldInfo m
+        -> FieldInfo m
+        -> ReaderT (Validation m) Seq Error
+    sameResponseShape fieldA fieldB =
+        let Full.Field _ _ _ _ selectionsA _ = node fieldA
+            Full.Field _ _ _ _ selectionsB _ = node fieldB
+         in case unwrapTypes (type' fieldA) (type' fieldB) of
+            Left True -> lift mempty
+            Right (compositeA, compositeB) -> do
+                validation <- ask
+                let collectFields' composite = flip runReaderT validation
+                        . flip evalStateT HashSet.empty
+                        . collectFields composite
+                let collectA = collectFields' compositeA selectionsA
+                let collectB = collectFields' compositeB selectionsB
+                fieldsInSetCanMerge
+                    $ foldl' (HashMap.unionWith (<>)) HashMap.empty
+                    $ collectA <> collectB
+            _ -> pure $ makeError (node fieldA) (node fieldB)
+    makeError fieldA fieldB =
+        let Full.Field aliasA fieldNameA _ _ _ locationA = fieldA
+            Full.Field _ fieldNameB _ _ _ locationB = fieldB
+            message = concat
+                [ "Fields \""
+                , Text.unpack (fromMaybe fieldNameA aliasA)
+                , "\" conflict because \""
+                , Text.unpack fieldNameB
+                , "\" and \""
+                , Text.unpack fieldNameA
+                , "\" are different fields. Use different aliases on the fields "
+                , "to fetch both if this was intentional."
+                ]
+             in Error message [locationB, locationA]
+    unwrapTypes typeA@Out.ScalarBaseType{} typeB@Out.ScalarBaseType{} =
+        Left $ typeA == typeB
+    unwrapTypes typeA@Out.EnumBaseType{} typeB@Out.EnumBaseType{} =
+        Left $ typeA == typeB
+    unwrapTypes (Out.ListType listA) (Out.ListType listB) =
+        unwrapTypes listA listB
+    unwrapTypes (Out.NonNullListType listA) (Out.NonNullListType listB) =
+        unwrapTypes listA listB
+    unwrapTypes typeA typeB
+        | Out.isNonNullType typeA == Out.isNonNullType typeB
+        , Just compositeA <- Type.outToComposite typeA
+        , Just compositeB <- Type.outToComposite typeB =
+            Right (compositeA, compositeB)
+        | otherwise = Left False
+    flattenPairs :: forall m
+        . HashMap Full.Name (NonEmpty (Full.Field, Type.CompositeType m))
+        -> (Seq (FieldInfo m), Seq (FieldInfo m, FieldInfo m))
+    flattenPairs xs = HashMap.foldr splitSingleFields (Seq.empty, Seq.empty)
+        $ foldr lookupTypeField [] <$> xs
+    splitSingleFields :: forall m
+        . [FieldInfo m]
+        -> (Seq (FieldInfo m), Seq (FieldInfo m, FieldInfo m))
+        -> (Seq (FieldInfo m), Seq (FieldInfo m, FieldInfo m))
+    splitSingleFields [head'] (fields, pairList) = (fields |> head', pairList)
+    splitSingleFields xs (fields, pairList) = (fields, pairs pairList xs)
+    lookupTypeField (field, parentType) accumulator =
+        let Full.Field _ fieldName _ _ _ _ = field
+         in case Type.lookupCompositeField fieldName parentType of
+            Nothing -> accumulator
+            Just (Out.Field _ typeField _) ->
+                FieldInfo field typeField parentType : accumulator
+    pairs :: forall m
+        . Seq (FieldInfo m, FieldInfo m)
+        -> [FieldInfo m]
+        -> Seq (FieldInfo m, FieldInfo m)
+    pairs accumulator [] = accumulator
+    pairs accumulator (fieldA : fields) =
+        pair fieldA (pairs accumulator fields) fields
+    pair _ accumulator [] = accumulator
+    pair field accumulator (fieldA : fields) =
+        pair field accumulator fields |> (field, fieldA)
+    collectFields objectType = accumulateFields objectType mempty
+    accumulateFields = foldM . forEach
+    forEach parentType accumulator = \case
+        Full.FieldSelection fieldSelection ->
+            forField parentType accumulator fieldSelection
+        Full.FragmentSpreadSelection fragmentSelection ->
+            forSpread accumulator fragmentSelection
+        Full.InlineFragmentSelection fragmentSelection ->
+            forInline parentType accumulator fragmentSelection
+    forField parentType accumulator field@(Full.Field alias fieldName _ _ _ _) =
+        let key = fromMaybe fieldName alias
+            value = (field, parentType) :| []
+         in pure $ HashMap.insertWith (<>) key value accumulator
+    forSpread accumulator (Full.FragmentSpread fragmentName _ _) = do
+        inVisitetFragments <- gets $ HashSet.member fragmentName
+        if inVisitetFragments
+            then pure accumulator
+            else collectFromSpread fragmentName accumulator
+    forInline parentType accumulator = \case
+        Full.InlineFragment maybeType _ selections _
+            | Just typeCondition <- maybeType ->
+                collectFromFragment typeCondition selections accumulator
+            | otherwise -> accumulateFields parentType accumulator $ toList selections
+    collectFromFragment typeCondition selectionSet' accumulator = do
+        types' <- lift $ asks $ Schema.types . schema
+        case Type.lookupTypeCondition typeCondition types' of
+            Nothing -> pure accumulator
+            Just compositeType ->
+                accumulateFields compositeType accumulator $ toList selectionSet'
+    collectFromSpread fragmentName accumulator = do
+        modify $ HashSet.insert fragmentName
+        ast' <- lift $ asks ast
+        case findFragmentDefinition fragmentName ast' of
+            Nothing -> pure accumulator
+            Just (Full.FragmentDefinition _ typeCondition _ selectionSet' _) ->
+                collectFromFragment typeCondition selectionSet' accumulator
+
+data FieldInfo m = FieldInfo
+    { node :: Full.Field
+    , type' :: Out.Type m
+    , parent :: Type.CompositeType m
+    }
+
+-- | Fragments are declared on a type and will only apply when the runtime
+-- object type matches the type condition. They also are spread within the
+-- context of a parent type. A fragment spread is only valid if its type
+-- condition could ever apply within the parent type.
+possibleFragmentSpreadsRule :: forall m. Rule m
+possibleFragmentSpreadsRule = SelectionRule go
+  where
+    go (Just parentType) (Full.InlineFragmentSelection fragmentSelection)
+        | Full.InlineFragment maybeType _ _ location' <- fragmentSelection
+        , Just typeCondition <- maybeType = do
+            (fragmentTypeName, parentTypeName) <-
+                compareTypes typeCondition parentType
+            pure $ Error
+                { message = concat
+                    [ "Fragment cannot be spread here as objects of type \""
+                    , Text.unpack parentTypeName
+                    , "\" can never be of type \""
+                    , Text.unpack fragmentTypeName
+                    , "\"."
+                    ]
+                , locations = [location']
+                }
+    go (Just parentType) (Full.FragmentSpreadSelection fragmentSelection)
+        | Full.FragmentSpread fragmentName _ location' <- fragmentSelection = do
+            typeCondition <- findSpreadTarget fragmentName
+            (fragmentTypeName, parentTypeName) <-
+                compareTypes typeCondition parentType
+            pure $ Error
+                { message = concat
+                    [ "Fragment \""
+                    , Text.unpack fragmentName
+                    , "\" cannot be spread here as objects of type \""
+                    , Text.unpack parentTypeName
+                    , "\" can never be of type \""
+                    , Text.unpack fragmentTypeName
+                    , "\"."
+                    ]
+                , locations = [location']
+                }
+    go _ _ = lift mempty
+    compareTypes typeCondition parentType = do
+        types' <- asks $ Schema.types . schema
+        fragmentType <- lift
+            $ maybeToSeq
+            $ Type.lookupTypeCondition typeCondition types'
+        parentComposite <- lift
+            $ maybeToSeq
+            $ Type.outToComposite parentType
+        possibleFragments <- getPossibleTypes fragmentType
+        possibleParents <- getPossibleTypes parentComposite
+        let fragmentTypeName = compositeTypeName fragmentType
+        let parentTypeName = compositeTypeName parentComposite
+        if HashSet.null $ HashSet.intersection possibleFragments possibleParents
+            then pure (fragmentTypeName, parentTypeName)
+            else lift mempty
+    getPossibleTypeList (Type.CompositeObjectType objectType) =
+        pure [Schema.ObjectType objectType]
+    getPossibleTypeList (Type.CompositeUnionType unionType) =
+        let Out.UnionType _ _ members = unionType
+         in pure $ Schema.ObjectType <$> members
+    getPossibleTypeList (Type.CompositeInterfaceType interfaceType) =
+        let Out.InterfaceType typeName _ _ _ = interfaceType
+         in HashMap.lookupDefault [] typeName
+        <$> asks (Schema.implementations . schema)
+    getPossibleTypes compositeType
+        = foldr (HashSet.insert . internalTypeName) HashSet.empty
+        <$> getPossibleTypeList compositeType
+
+internalTypeName :: forall m. Schema.Type m -> Full.Name
+internalTypeName (Schema.ScalarType (Definition.ScalarType typeName _)) =
+    typeName
+internalTypeName (Schema.EnumType (Definition.EnumType typeName _ _)) = typeName
+internalTypeName (Schema.ObjectType (Out.ObjectType typeName _ _ _)) = typeName
+internalTypeName (Schema.InputObjectType (In.InputObjectType typeName _ _)) =
+    typeName
+internalTypeName (Schema.InterfaceType (Out.InterfaceType typeName _ _ _)) =
+    typeName
+internalTypeName (Schema.UnionType (Out.UnionType typeName _ _)) = typeName
+
+findSpreadTarget :: Full.Name -> ReaderT (Validation m1) Seq Full.TypeCondition
+findSpreadTarget fragmentName = do
+    ast' <- asks ast
+    let target = find (isSpreadTarget fragmentName) ast'
+    lift $ maybeToSeq $ target >>= extractTypeCondition
+  where
+    extractTypeCondition (viewFragment -> Just fragmentDefinition) =
+        let Full.FragmentDefinition _ typeCondition _ _ _ = fragmentDefinition
+            in Just typeCondition
+    extractTypeCondition _ = Nothing
+
+visitFragmentDefinition :: forall m
+    . Text
+    -> ValidationState m (Maybe Full.FragmentDefinition)
+visitFragmentDefinition fragmentName = do
+    definitions <- lift $ asks ast
+    visited <- gets (HashSet.member fragmentName)
+    modify (HashSet.insert fragmentName)
+    case find (isSpreadTarget fragmentName) definitions of
+        Just (viewFragment -> Just fragmentDefinition)
+            | not visited -> pure $ Just fragmentDefinition
+        _ -> pure Nothing
+
+-- | Variable usages must be compatible with the arguments they are passed to.
+--
+-- Validation failures occur when variables are used in the context of types
+-- that are complete mismatches, or if a nullable type in a variable is passed
+-- to a non‐null argument type.
+variablesInAllowedPositionRule :: forall m. Rule m
+variablesInAllowedPositionRule = OperationDefinitionRule $ \case
+    Full.OperationDefinition operationType _ variables _ selectionSet _ -> do
+        schema' <- asks schema
+        let root = go variables (toList selectionSet) . Type.CompositeObjectType
+        case operationType of
+            Full.Query -> root $ Schema.query schema'
+            Full.Mutation
+                | Just objectType <- Schema.mutation schema' -> root objectType
+            Full.Subscription
+                | Just objectType <- Schema.mutation schema' -> root objectType
+            _ -> lift mempty
+    _ -> lift mempty
+  where
+    go variables selections selectionType = mapReaderT (foldr (<>) Seq.empty)
+        $ flip evalStateT HashSet.empty
+        $ visitSelectionSet variables selectionType
+        $ toList selections
+    visitSelectionSet :: Foldable t
+        => [Full.VariableDefinition]
+        -> Type.CompositeType m
+        -> t Full.Selection
+        -> ValidationState m (Seq Error)
+    visitSelectionSet variables selectionType selections =
+        foldM (evaluateSelection variables selectionType) mempty selections
+    evaluateFieldSelection variables selections accumulator = \case
+        Just newParentType -> do
+            let folder = evaluateSelection variables newParentType
+            selectionErrors <- foldM folder accumulator selections
+            pure $ accumulator <> selectionErrors
+        Nothing -> pure accumulator
+    evaluateSelection :: [Full.VariableDefinition]
+        -> Type.CompositeType m
+        -> Seq Error
+        -> Full.Selection
+        -> ValidationState m (Seq Error)
+    evaluateSelection variables selectionType accumulator selection
+        | Full.FragmentSpreadSelection spread <- selection
+        , Full.FragmentSpread fragmentName _ _ <- spread = do
+            types' <- lift $ asks $ Schema.types . schema
+            nonVisitedFragmentDefinition <- visitFragmentDefinition fragmentName
+            case nonVisitedFragmentDefinition of
+                Just fragmentDefinition
+                    | Full.FragmentDefinition _ typeCondition _ _ _ <- fragmentDefinition
+                    , Just spreadType <- Type.lookupTypeCondition typeCondition types' -> do
+                        spreadErrors <- spreadVariables variables spread
+                        selectionErrors <- diveIntoSpread variables spreadType fragmentDefinition
+                        pure $ accumulator <> spreadErrors <> selectionErrors
+                _ -> lift $ lift mempty
+        | Full.FieldSelection fieldSelection <- selection
+        , Full.Field _ fieldName _ _ subselections _ <- fieldSelection =
+            case Type.lookupCompositeField fieldName selectionType of
+                Just (Out.Field _ typeField argumentTypes) -> do
+                    fieldErrors <- fieldVariables variables argumentTypes fieldSelection
+                    selectionErrors <- evaluateFieldSelection variables subselections accumulator
+                            $ Type.outToComposite typeField
+                    pure $ selectionErrors <> fieldErrors
+                Nothing -> pure accumulator
+        | Full.InlineFragmentSelection inlineSelection <- selection
+        , Full.InlineFragment typeCondition _ subselections _ <- inlineSelection = do
+            types' <- lift $ asks $ Schema.types . schema
+            let inlineType = fromMaybe selectionType
+                    $ typeCondition >>= flip Type.lookupTypeCondition types'
+            fragmentErrors <- inlineVariables variables inlineSelection
+            let folder = evaluateSelection variables inlineType
+            selectionErrors <- foldM folder accumulator subselections
+            pure $ accumulator <> fragmentErrors <> selectionErrors
+    inlineVariables variables inline
+        | Full.InlineFragment _ directives' _ _ <- inline =
+            mapDirectives variables directives'
+    fieldVariables :: [Full.VariableDefinition]
+        -> In.Arguments
+        -> Full.Field
+        -> ValidationState m (Seq Error)
+    fieldVariables variables argumentTypes fieldSelection = do
+        let Full.Field _ _ arguments directives' _ _ = fieldSelection
+        argumentErrors <- mapArguments variables argumentTypes arguments
+        directiveErrors <- mapDirectives variables directives'
+        pure $ argumentErrors <> directiveErrors
+    spreadVariables variables (Full.FragmentSpread _ directives' _) =
+        mapDirectives variables directives'
+    diveIntoSpread variables fieldType fragmentDefinition = do
+        let Full.FragmentDefinition _ _ directives' selections _ =
+                fragmentDefinition
+        selectionErrors <- visitSelectionSet variables fieldType selections
+        directiveErrors <- mapDirectives variables directives'
+        pure $ selectionErrors <> directiveErrors
+    findDirectiveVariables variables directive = do
+        let Full.Directive directiveName arguments _ = directive
+        directiveDefinitions <- lift $ asks $ Schema.directives . schema
+        case HashMap.lookup directiveName directiveDefinitions of
+            Just (Schema.Directive _ _ directiveArguments) ->
+                mapArguments variables directiveArguments arguments
+            Nothing -> pure mempty
+    mapArguments variables argumentTypes = fmap fold
+        . traverse (findArgumentVariables variables argumentTypes)
+    mapDirectives variables = fmap fold
+        <$> traverse (findDirectiveVariables variables)
+    lookupInputObject variables objectFieldValue locationInfo
+        | Full.Node{ node = Full.Object objectFields } <- objectFieldValue
+        , Just (expectedType, _) <- locationInfo
+        , In.InputObjectBaseType inputObjectType <- expectedType
+        , In.InputObjectType _ _ fieldTypes' <- inputObjectType =
+            fold <$> traverse (traverseObjectField variables fieldTypes') objectFields
+        | otherwise = pure mempty
+    maybeUsageAllowed variableName variables locationInfo
+        | Just (locationType, locationValue) <- locationInfo
+        , findVariableDefinition' <- findVariableDefinition variableName
+        , Just variableDefinition <- find findVariableDefinition' variables
+            = maybeToSeq
+            <$> isVariableUsageAllowed locationType locationValue variableDefinition
+        | otherwise = pure mempty
+    findArgumentVariables :: [Full.VariableDefinition]
+        -> HashMap Full.Name In.Argument
+        -> Full.Argument
+        -> ValidationState m (Seq Error)
+    findArgumentVariables variables argumentTypes argument
+        | Full.Argument argumentName argumentValue _ <- argument
+        , Full.Node{ node = Full.Variable variableName } <- argumentValue
+            = maybeUsageAllowed variableName variables
+            $ locationPair extractArgument argumentTypes argumentName
+        | Full.Argument argumentName argumentValue _ <- argument
+            = lookupInputObject variables argumentValue
+            $ locationPair extractArgument argumentTypes argumentName
+    extractField (In.InputField _ locationType locationValue) =
+        (locationType, locationValue)
+    extractArgument (In.Argument _ locationType locationValue) =
+        (locationType, locationValue)
+    locationPair extract fieldTypes name =
+        extract <$> HashMap.lookup name fieldTypes
+    traverseObjectField variables fieldTypes Full.ObjectField{..}
+        | Full.Node{ node = Full.Variable variableName } <- value
+            = maybeUsageAllowed variableName variables
+            $ locationPair extractField fieldTypes name
+        | otherwise = lookupInputObject variables value
+            $  locationPair extractField fieldTypes name
+    findVariableDefinition variableName variableDefinition =
+        let Full.VariableDefinition variableName' _ _ _ = variableDefinition
+         in variableName == variableName'
+    isVariableUsageAllowed locationType locationDefaultValue variableDefinition
+        | Full.VariableDefinition _ variableType _ _ <- variableDefinition
+        , Full.TypeNonNull _ <- variableType =
+            typesCompatibleOrError variableDefinition locationType
+        | Just nullableLocationType <- unwrapInType locationType
+        , Full.VariableDefinition _ variableType variableDefaultValue _ <-
+            variableDefinition
+        , hasNonNullVariableDefaultValue' <-
+            hasNonNullVariableDefaultValue variableDefaultValue
+        , hasLocationDefaultValue <- isJust locationDefaultValue =
+            if (hasNonNullVariableDefaultValue' || hasLocationDefaultValue)
+                && areTypesCompatible variableType nullableLocationType
+                then pure Nothing
+                else pure $ makeError variableDefinition locationType
+        | otherwise = typesCompatibleOrError variableDefinition locationType
+    typesCompatibleOrError variableDefinition locationType
+        | Full.VariableDefinition _ variableType _ _ <- variableDefinition
+        , areTypesCompatible variableType locationType = pure Nothing
+        | otherwise = pure $ makeError variableDefinition locationType
+    areTypesCompatible nonNullType (unwrapInType -> Just nullableLocationType)
+        | Full.TypeNonNull (Full.NonNullTypeNamed namedType) <- nonNullType =
+            areTypesCompatible (Full.TypeNamed namedType) nullableLocationType
+        | Full.TypeNonNull (Full.NonNullTypeList namedList) <- nonNullType =
+            areTypesCompatible (Full.TypeList namedList) nullableLocationType
+    areTypesCompatible _ (In.isNonNullType -> True) = False
+    areTypesCompatible (Full.TypeNonNull nonNullType) locationType
+        | Full.NonNullTypeNamed namedType <- nonNullType =
+            areTypesCompatible (Full.TypeNamed namedType) locationType
+        | Full.NonNullTypeList namedType <- nonNullType =
+            areTypesCompatible (Full.TypeList namedType) locationType
+    areTypesCompatible variableType locationType
+        | Full.TypeList itemVariableType <- variableType
+        , In.ListType itemLocationType <- locationType =
+            areTypesCompatible itemVariableType itemLocationType
+        | areIdentical variableType locationType = True
+        | otherwise = False
+    areIdentical (Full.TypeList typeList) (In.ListType itemLocationType) =
+        areIdentical typeList itemLocationType
+    areIdentical (Full.TypeNonNull nonNullType) locationType
+        | Full.NonNullTypeList nonNullList <- nonNullType
+        , In.NonNullListType  itemLocationType <- locationType =
+            areIdentical nonNullList itemLocationType
+        | Full.NonNullTypeNamed _ <- nonNullType
+        , In.ListBaseType _ <- locationType = False
+        | Full.NonNullTypeNamed nonNullList <- nonNullType
+        , In.isNonNullType locationType =
+            nonNullList == inputTypeName locationType
+    areIdentical (Full.TypeNamed _) (In.ListBaseType _) = False
+    areIdentical (Full.TypeNamed typeNamed) locationType
+        | not $ In.isNonNullType locationType =
+            typeNamed == inputTypeName locationType
+    areIdentical _ _ = False
+    hasNonNullVariableDefaultValue (Just (Full.Node Full.ConstNull _)) = False
+    hasNonNullVariableDefaultValue Nothing = False
+    hasNonNullVariableDefaultValue _ = True
+    unwrapInType (In.NonNullScalarType nonNullType) =
+        Just $ In.NamedScalarType nonNullType
+    unwrapInType (In.NonNullEnumType nonNullType) =
+        Just $ In.NamedEnumType nonNullType
+    unwrapInType (In.NonNullInputObjectType nonNullType) =
+        Just $ In.NamedInputObjectType nonNullType
+    unwrapInType (In.NonNullListType nonNullType) =
+        Just $ In.ListType nonNullType
+    unwrapInType _ = Nothing
+    makeError variableDefinition expectedType =
+        let Full.VariableDefinition variableName variableType _ location' =
+                variableDefinition
+         in Just $ Error
+            { message = concat
+                [ "Variable \"$"
+                , Text.unpack variableName
+                , "\" of type \""
+                , show variableType
+                , "\" used in position expecting type \""
+                , show expectedType
+                , "\"."
+                ]
+            , locations = [location']
+            }
+
+-- | Literal values must be compatible with the type expected in the position
+-- they are found as per the coercion rules.
+--
+-- The type expected in a position include the type defined by the argument a
+-- value is provided for, the type defined by an input object field a value is
+-- provided for, and the type of a variable definition a default value is
+-- provided for.
+valuesOfCorrectTypeRule :: forall m. Rule m
+valuesOfCorrectTypeRule = ValueRule go constGo
+  where
+    go (Just inputType) value
+        | Just constValue <- toConstNode value =
+            lift $ check inputType constValue
+    go _ _ = lift mempty
+    toConstNode Full.Node{..} = flip Full.Node location <$> toConst node
+    toConst (Full.Variable _) = Nothing
+    toConst (Full.Int integer) = Just $ Full.ConstInt integer
+    toConst (Full.Float double) = Just $ Full.ConstFloat double
+    toConst (Full.String string) = Just $ Full.ConstString string
+    toConst (Full.Boolean boolean) = Just $ Full.ConstBoolean boolean
+    toConst Full.Null = Just Full.ConstNull
+    toConst (Full.Enum enum) = Just $ Full.ConstEnum enum
+    toConst (Full.List values) =
+        Just $ Full.ConstList $ catMaybes $ toConst <$> values
+    toConst (Full.Object fields) = Just $ Full.ConstObject
+        $ catMaybes $ constObjectField <$> fields
+    constObjectField Full.ObjectField{..}
+        | Just constValue <- toConstNode value =
+            Just $ Full.ObjectField name constValue location
+        | otherwise = Nothing
+    constGo Nothing = const $ lift mempty
+    constGo (Just inputType) = lift . check inputType
+    check :: In.Type -> Full.Node Full.ConstValue -> Seq Error
+    check _ Full.Node{ node = Full.ConstNull } =
+        mempty -- Ignore, required fields are checked elsewhere.
+    check (In.ScalarBaseType scalarType) Full.Node{ node }
+        | Definition.ScalarType "Int" _ <- scalarType
+        , Full.ConstInt _ <- node = mempty
+        | Definition.ScalarType "Boolean" _ <- scalarType
+        , Full.ConstBoolean _ <- node = mempty
+        | Definition.ScalarType "String" _ <- scalarType
+        , Full.ConstString _ <- node = mempty
+        | Definition.ScalarType "ID" _ <- scalarType
+        , Full.ConstString _ <- node = mempty
+        | Definition.ScalarType "ID" _ <- scalarType
+        , Full.ConstInt _ <- node = mempty
+        | Definition.ScalarType "Float" _ <- scalarType
+        , Full.ConstFloat _ <- node = mempty
+        | Definition.ScalarType "Float" _ <- scalarType
+        , Full.ConstInt _ <- node = mempty
+    check (In.EnumBaseType enumType) Full.Node{ node }
+        | Definition.EnumType _ _ members <- enumType
+        , Full.ConstEnum memberValue <- node
+        , HashMap.member memberValue members = mempty
+    check (In.InputObjectBaseType objectType) Full.Node{ node }
+        | In.InputObjectType _ _ typeFields <- objectType
+        , Full.ConstObject valueFields <- node =
+            foldMap (checkObjectField typeFields) valueFields
+    check (In.ListBaseType listType) constValue@Full.Node{ .. }
+        | Full.ConstList listValues <- node =
+            foldMap (check listType) $ flip Full.Node location <$> listValues
+        | otherwise = check listType constValue
+    check inputType Full.Node{ .. } = pure $ Error
+        { message = concat
+            [ "Value "
+            , show node, " cannot be coerced to type \""
+            , show inputType
+            , "\"."
+            ]
+        , locations = [location]
+        }
+    checkObjectField typeFields Full.ObjectField{..}
+        | Just typeField <- HashMap.lookup name typeFields
+        , In.InputField _ fieldType _ <- typeField =
+            check fieldType value
+    checkObjectField _ _ = mempty

stack.yaml

@@ -1,4 +1,4 @@
-resolver: lts-16.20
+resolver: lts-17.2
 
 packages:
 - .

tests/Language/GraphQL/AST/DocumentSpec.hs

@@ -0,0 +1,20 @@
+{-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE OverloadedStrings #-}
+module Language.GraphQL.AST.DocumentSpec
+    ( spec
+    ) where
+
+import Language.GraphQL.AST.Document
+import Test.Hspec (Spec, describe, it, shouldBe)
+
+spec :: Spec
+spec = do
+    describe "Document" $ do
+        it "shows objects" $
+            let zero = Location 0 0
+                object = ConstObject
+                    [ ObjectField "field1" (Node (ConstFloat 1.2) zero) zero
+                    , ObjectField "field2" (Node ConstNull zero) zero
+                    ]
+                expected = "{ field1: 1.2, field2: null }"
+             in show object `shouldBe` expected

tests/Language/GraphQL/Validate/RulesSpec.hs

@@ -0,0 +1,914 @@
+{- This Source Code Form is subject to the terms of the Mozilla Public License,
+   v. 2.0. If a copy of the MPL was not distributed with this file, You can
+   obtain one at https://mozilla.org/MPL/2.0/. -}
+
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module Language.GraphQL.Validate.RulesSpec
+    ( spec
+    ) where
+
+import Data.Foldable (toList)
+import qualified Data.HashMap.Strict as HashMap
+import Data.Text (Text)
+import qualified Language.GraphQL.AST as AST
+import Language.GraphQL.Type
+import qualified Language.GraphQL.Type.In as In
+import qualified Language.GraphQL.Type.Out as Out
+import Language.GraphQL.Validate
+import Test.Hspec (Spec, context, describe, it, shouldBe, shouldContain)
+import Text.Megaparsec (parse, errorBundlePretty)
+import Text.RawString.QQ (r)
+
+petSchema :: Schema IO
+petSchema = schema queryType Nothing (Just subscriptionType) mempty
+
+queryType :: ObjectType IO
+queryType = ObjectType "Query" Nothing [] $ HashMap.fromList
+    [ ("dog", dogResolver)
+    , ("cat", catResolver)
+    , ("findDog", findDogResolver)
+    ]
+  where
+    dogField = Field Nothing (Out.NamedObjectType dogType) mempty
+    dogResolver = ValueResolver dogField $ pure Null
+    findDogArguments = HashMap.singleton "complex"
+        $ In.Argument Nothing (In.NonNullInputObjectType dogDataType) Nothing
+    findDogField = Field Nothing (Out.NamedObjectType dogType) findDogArguments
+    findDogResolver = ValueResolver findDogField $ pure Null
+    catField = Field Nothing (Out.NamedObjectType catType) mempty
+    catResolver = ValueResolver catField $ pure Null
+
+catCommandType :: EnumType
+catCommandType = EnumType "CatCommand" Nothing $ HashMap.fromList
+    [ ("JUMP", EnumValue Nothing)
+    ]
+
+catType :: ObjectType IO
+catType = ObjectType "Cat" Nothing [petType] $ HashMap.fromList
+    [ ("name", nameResolver)
+    , ("nickname", nicknameResolver)
+    , ("doesKnowCommand", doesKnowCommandResolver)
+    , ("meowVolume", meowVolumeResolver)
+    ]
+  where
+    meowVolumeField = Field Nothing (Out.NamedScalarType int) mempty
+    meowVolumeResolver = ValueResolver meowVolumeField $ pure $ Int 3
+    doesKnowCommandField = Field Nothing (Out.NonNullScalarType boolean)
+        $ HashMap.singleton "catCommand"
+        $ In.Argument Nothing (In.NonNullEnumType catCommandType) Nothing
+    doesKnowCommandResolver = ValueResolver doesKnowCommandField
+        $ pure $ Boolean True
+
+nameResolver :: Resolver IO
+nameResolver = ValueResolver nameField $ pure "Name"
+  where
+    nameField = Field Nothing (Out.NonNullScalarType string) mempty
+
+nicknameResolver :: Resolver IO
+nicknameResolver = ValueResolver nicknameField $ pure "Nickname"
+  where
+    nicknameField = Field Nothing (Out.NamedScalarType string) mempty
+
+dogCommandType :: EnumType
+dogCommandType = EnumType "DogCommand" Nothing $ HashMap.fromList
+    [ ("SIT", EnumValue Nothing)
+    , ("DOWN", EnumValue Nothing)
+    , ("HEEL", EnumValue Nothing)
+    ]
+
+dogType :: ObjectType IO
+dogType = ObjectType "Dog" Nothing [petType] $ HashMap.fromList
+    [ ("name", nameResolver)
+    , ("nickname", nicknameResolver)
+    , ("barkVolume", barkVolumeResolver)
+    , ("doesKnowCommand", doesKnowCommandResolver)
+    , ("isHousetrained", isHousetrainedResolver)
+    , ("owner", ownerResolver)
+    ]
+  where
+    barkVolumeField = Field Nothing (Out.NamedScalarType int) mempty
+    barkVolumeResolver = ValueResolver barkVolumeField $ pure $ Int 3
+    doesKnowCommandField = Field Nothing (Out.NonNullScalarType boolean)
+        $ HashMap.singleton "dogCommand"
+        $ In.Argument Nothing (In.NonNullEnumType dogCommandType) Nothing
+    doesKnowCommandResolver = ValueResolver doesKnowCommandField
+        $ pure $ Boolean True
+    isHousetrainedField = Field Nothing (Out.NonNullScalarType boolean)
+        $ HashMap.singleton "atOtherHomes"
+        $ In.Argument Nothing (In.NamedScalarType boolean) Nothing
+    isHousetrainedResolver = ValueResolver isHousetrainedField
+        $ pure $ Boolean True
+    ownerField = Field Nothing (Out.NamedObjectType humanType) mempty
+    ownerResolver = ValueResolver ownerField $ pure Null
+
+dogDataType :: InputObjectType
+dogDataType = InputObjectType "DogData" Nothing
+    $ HashMap.singleton "name" nameInputField
+  where
+    nameInputField = InputField Nothing (In.NonNullScalarType string) Nothing
+
+sentientType :: InterfaceType IO
+sentientType = InterfaceType "Sentient" Nothing []
+    $ HashMap.singleton "name"
+    $ Field Nothing (Out.NonNullScalarType string) mempty
+
+petType :: InterfaceType IO
+petType = InterfaceType "Pet" Nothing []
+    $ HashMap.singleton "name"
+    $ Field Nothing (Out.NonNullScalarType string) mempty
+
+subscriptionType :: ObjectType IO
+subscriptionType = ObjectType "Subscription" Nothing [] $ HashMap.fromList
+    [ ("newMessage", newMessageResolver)
+    , ("disallowedSecondRootField", newMessageResolver)
+    ]
+  where
+    newMessageField = Field Nothing (Out.NonNullObjectType messageType) mempty
+    newMessageResolver = ValueResolver newMessageField
+        $ pure $ Object HashMap.empty
+
+messageType :: ObjectType IO
+messageType = ObjectType "Message" Nothing [] $ HashMap.fromList
+    [ ("sender", senderResolver)
+    , ("body", bodyResolver)
+    ]
+  where
+    senderField = Field Nothing (Out.NonNullScalarType string) mempty
+    senderResolver = ValueResolver senderField $ pure "Sender"
+    bodyField = Field Nothing (Out.NonNullScalarType string) mempty
+    bodyResolver = ValueResolver bodyField $ pure "Message body."
+
+humanType :: ObjectType IO
+humanType = ObjectType "Human" Nothing [sentientType] $ HashMap.fromList
+    [ ("name", nameResolver)
+    , ("pets", petsResolver)
+    ]
+  where
+    petsField =
+        Field Nothing (Out.ListType $ Out.NonNullInterfaceType petType) mempty
+    petsResolver = ValueResolver petsField $ pure $ List []
+
+validate :: Text -> [Error]
+validate queryString =
+    case parse AST.document "" queryString of
+        Left parseErrors -> error $ errorBundlePretty parseErrors
+        Right ast -> toList $ document petSchema specifiedRules ast
+
+spec :: Spec
+spec =
+    describe "document" $ do
+        context "executableDefinitionsRule" $
+            it "rejects type definitions" $
+                let queryString = [r|
+                  query getDogName {
+                    dog {
+                      name
+                      color
+                    }
+                  }
+
+                  extend type Dog {
+                    color: String
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Definition must be OperationDefinition or \
+                            \FragmentDefinition."
+                        , locations = [AST.Location 9 19]
+                        }
+                 in validate queryString `shouldContain` [expected]
+
+        context "singleFieldSubscriptionsRule" $ do
+            it "rejects multiple subscription root fields" $
+                let queryString = [r|
+                  subscription sub {
+                    newMessage {
+                      body
+                      sender
+                    }
+                    disallowedSecondRootField
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Subscription \"sub\" must select only one top \
+                            \level field."
+                        , locations = [AST.Location 2 19]
+                        }
+                 in validate queryString `shouldContain` [expected]
+
+            it "rejects multiple subscription root fields coming from a fragment" $
+                let queryString = [r|
+                  subscription sub {
+                    ...multipleSubscriptions
+                  }
+
+                  fragment multipleSubscriptions on Subscription {
+                    newMessage {
+                      body
+                      sender
+                    }
+                    disallowedSecondRootField
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Subscription \"sub\" must select only one top \
+                            \level field."
+                        , locations = [AST.Location 2 19]
+                        }
+                 in validate queryString `shouldContain` [expected]
+
+            it "finds corresponding subscription fragment" $
+                let queryString = [r|
+                  subscription sub {
+                    ...anotherSubscription
+                    ...multipleSubscriptions
+                  }
+                  fragment multipleSubscriptions on Subscription {
+                    newMessage {
+                      body
+                    }
+                    disallowedSecondRootField {
+                      sender
+                    }
+                  }
+                  fragment anotherSubscription on Subscription {
+                    newMessage {
+                      body
+                      sender
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Subscription \"sub\" must select only one top \
+                            \level field."
+                        , locations = [AST.Location 2 19]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "loneAnonymousOperationRule" $
+            it "rejects multiple anonymous operations" $
+                let queryString = [r|
+                  {
+                    dog {
+                      name
+                    }
+                  }
+
+                  query getName {
+                    dog {
+                      owner {
+                        name
+                      }
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "This anonymous operation must be the only defined \
+                            \operation."
+                        , locations = [AST.Location 2 19]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "uniqueOperationNamesRule" $
+            it "rejects operations with the same name" $
+                let queryString = [r|
+                  query dogOperation {
+                    dog {
+                      name
+                    }
+                  }
+
+                  mutation dogOperation {
+                    mutateDog {
+                      id
+                    }
+                }
+                |]
+                    expected = Error
+                        { message =
+                            "There can be only one operation named \
+                            \\"dogOperation\"."
+                        , locations = [AST.Location 2 19, AST.Location 8 19]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "uniqueFragmentNamesRule" $
+            it "rejects fragments with the same name" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ...fragmentOne
+                    }
+                  }
+
+                  fragment fragmentOne on Dog {
+                    name
+                  }
+
+                  fragment fragmentOne on Dog {
+                    owner {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "There can be only one fragment named \
+                            \\"fragmentOne\"."
+                        , locations = [AST.Location 8 19, AST.Location 12 19]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "fragmentSpreadTargetDefinedRule" $
+            it "rejects the fragment spread without a target" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ...undefinedFragment
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment target \"undefinedFragment\" is \
+                            \undefined."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "fragmentSpreadTypeExistenceRule" $ do
+            it "rejects fragment spreads without an unknown target type" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ...notOnExistingType
+                    }
+                  }
+                  fragment notOnExistingType on NotInSchema {
+                    name
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment \"notOnExistingType\" is specified on \
+                            \type \"NotInSchema\" which doesn't exist in the \
+                            \schema."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "rejects inline fragments without a target" $
+                let queryString = [r|
+                  {
+                    ... on NotInSchema {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Inline fragment is specified on type \
+                            \\"NotInSchema\" which doesn't exist in the schema."
+                        , locations = [AST.Location 3 21]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "fragmentsOnCompositeTypesRule" $ do
+            it "rejects fragments on scalar types" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ...fragOnScalar
+                    }
+                  }
+                  fragment fragOnScalar on Int {
+                    name
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment cannot condition on non composite type \
+                            \\"Int\"."
+                        , locations = [AST.Location 7 19]
+                        }
+                 in validate queryString `shouldContain` [expected]
+
+            it "rejects inline fragments on scalar types" $
+                let queryString = [r|
+                  {
+                    ... on Boolean {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment cannot condition on non composite type \
+                            \\"Boolean\"."
+                        , locations = [AST.Location 3 21]
+                        }
+                in validate queryString `shouldContain` [expected]
+
+        context "noUnusedFragmentsRule" $
+            it "rejects unused fragments" $
+                let queryString = [r|
+                  fragment nameFragment on Dog { # unused
+                    name
+                  }
+
+                  {
+                    dog {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment \"nameFragment\" is never used."
+                        , locations = [AST.Location 2 19]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "noFragmentCyclesRule" $
+            it "rejects spreads that form cycles" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ...nameFragment
+                    }
+                  }
+                  fragment nameFragment on Dog {
+                    name
+                    ...barkVolumeFragment
+                  }
+                  fragment barkVolumeFragment on Dog {
+                    barkVolume
+                    ...nameFragment
+                  }
+                |]
+                    error1 = Error
+                        { message =
+                            "Cannot spread fragment \"barkVolumeFragment\" \
+                            \within itself (via barkVolumeFragment -> \
+                            \nameFragment -> barkVolumeFragment)."
+                        , locations = [AST.Location 11 19]
+                        }
+                    error2 = Error
+                        { message =
+                            "Cannot spread fragment \"nameFragment\" within \
+                            \itself (via nameFragment -> barkVolumeFragment -> \
+                            \nameFragment)."
+                        , locations = [AST.Location 7 19]
+                        }
+                 in validate queryString `shouldBe` [error1, error2]
+
+        context "uniqueArgumentNamesRule" $
+            it "rejects duplicate field arguments" $
+                let queryString = [r|
+                  {
+                    dog {
+                      isHousetrained(atOtherHomes: true, atOtherHomes: true)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "There can be only one argument named \
+                            \\"atOtherHomes\"."
+                        , locations = [AST.Location 4 38, AST.Location 4 58]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "uniqueDirectiveNamesRule" $
+            it "rejects more than one directive per location" $
+                let queryString = [r|
+                  query ($foo: Boolean = true, $bar: Boolean = false) {
+                    dog @skip(if: $foo) @skip(if: $bar) {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "There can be only one directive named \"skip\"."
+                        , locations = [AST.Location 3 25, AST.Location 3 41]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "uniqueVariableNamesRule" $
+            it "rejects duplicate variables" $
+                let queryString = [r|
+                  query houseTrainedQuery($atOtherHomes: Boolean, $atOtherHomes: Boolean) {
+                    dog {
+                      isHousetrained(atOtherHomes: $atOtherHomes)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "There can be only one variable named \
+                            \\"atOtherHomes\"."
+                        , locations = [AST.Location 2 43, AST.Location 2 67]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "variablesAreInputTypesRule" $
+            it "rejects non-input types as variables" $
+                let queryString = [r|
+                  query takesDogBang($dog: Dog!) {
+                    dog {
+                      isHousetrained(atOtherHomes: $dog)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Variable \"$dog\" cannot be non-input type \
+                            \\"Dog\"."
+                        , locations = [AST.Location 2 38]
+                        }
+                 in validate queryString `shouldContain` [expected]
+
+        context "noUndefinedVariablesRule" $
+            it "rejects undefined variables" $
+                let queryString = [r|
+                  query variableIsNotDefinedUsedInSingleFragment {
+                    dog {
+                      ...isHousetrainedFragment
+                    }
+                  }
+
+                  fragment isHousetrainedFragment on Dog {
+                    isHousetrained(atOtherHomes: $atOtherHomes)
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Variable \"$atOtherHomes\" is not defined by \
+                            \operation \
+                            \\"variableIsNotDefinedUsedInSingleFragment\"."
+                        , locations = [AST.Location 9 50]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "noUnusedVariablesRule" $
+            it "rejects unused variables" $
+                let queryString = [r|
+                  query variableUnused($atOtherHomes: Boolean) {
+                    dog {
+                      isHousetrained
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Variable \"$atOtherHomes\" is never used in \
+                            \operation \"variableUnused\"."
+                        , locations = [AST.Location 2 40]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "uniqueInputFieldNamesRule" $
+            it "rejects duplicate fields in input objects" $
+                let queryString = [r|
+                  {
+                    findDog(complex: { name: "Fido", name: "Jack" }) {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "There can be only one input field named \"name\"."
+                        , locations = [AST.Location 3 40, AST.Location 3 54]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "fieldsOnCorrectTypeRule" $
+            it "rejects undefined fields" $
+                let queryString = [r|
+                  {
+                    dog {
+                      meowVolume
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Cannot query field \"meowVolume\" on type \"Dog\"."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "scalarLeafsRule" $
+            it "rejects scalar fields with not empty selection set" $
+                let queryString = [r|
+                  {
+                    dog {
+                      barkVolume {
+                        sinceWhen
+                      }
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Field \"barkVolume\" must not have a selection \
+                            \since type \"Int\" has no subfields."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "knownArgumentNamesRule" $ do
+            it "rejects field arguments missing in the type" $
+                let queryString = [r|
+                  {
+                    dog {
+                      doesKnowCommand(command: CLEAN_UP_HOUSE, dogCommand: SIT)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Unknown argument \"command\" on field \
+                            \\"Dog.doesKnowCommand\"."
+                        , locations = [AST.Location 4 39]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "rejects directive arguments missing in the definition" $
+                let queryString = [r|
+                  {
+                    dog {
+                      isHousetrained(atOtherHomes: true) @include(unless: false, if: true)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Unknown argument \"unless\" on directive \
+                            \\"@include\"."
+                        , locations = [AST.Location 4 67]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "knownDirectiveNamesRule" $
+            it "rejects undefined directives" $
+                let queryString = [r|
+                  {
+                    dog {
+                      isHousetrained(atOtherHomes: true) @ignore(if: true)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message = "Unknown directive \"@ignore\"."
+                        , locations = [AST.Location 4 58]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "knownInputFieldNamesRule" $
+            it "rejects undefined input object fields" $
+                let queryString = [r|
+                  {
+                    findDog(complex: { favoriteCookieFlavor: "Bacon", name: "Jack" }) {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Field \"favoriteCookieFlavor\" is not defined \
+                            \by type \"DogData\"."
+                        , locations = [AST.Location 3 40]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "directivesInValidLocationsRule" $
+            it "rejects directives in invalid locations" $
+                let queryString = [r|
+                  query @skip(if: $foo) {
+                    dog {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Directive \"@skip\" may not be used on QUERY."
+                        , locations = [AST.Location 2 25]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "overlappingFieldsCanBeMergedRule" $ do
+            it "fails to merge fields of mismatching types" $
+                let queryString = [r|
+                  {
+                    dog {
+                      name: nickname
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fields \"name\" conflict because \"nickname\" and \
+                            \\"name\" are different fields. Use different \
+                            \aliases on the fields to fetch both if this was \
+                            \intentional."
+                        , locations = [AST.Location 4 23, AST.Location 5 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "fails if the arguments of the same field don't match" $
+                let queryString = [r|
+                  {
+                    dog {
+                      doesKnowCommand(dogCommand: SIT)
+                      doesKnowCommand(dogCommand: HEEL)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fields \"doesKnowCommand\" conflict because they \
+                            \have different arguments. Use different aliases \
+                            \on the fields to fetch both if this was \
+                            \intentional."
+                        , locations = [AST.Location 4 23, AST.Location 5 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "fails to merge same-named field and alias" $
+                let queryString = [r|
+                  {
+                    dog {
+                      doesKnowCommand(dogCommand: SIT)
+                      doesKnowCommand: isHousetrained(atOtherHomes: true)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fields \"doesKnowCommand\" conflict because \
+                            \\"doesKnowCommand\" and \"isHousetrained\" are \
+                            \different fields. Use different aliases on the \
+                            \fields to fetch both if this was intentional."
+                        , locations = [AST.Location 4 23, AST.Location 5 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "looks for fields after a successfully merged field pair" $
+                let queryString = [r|
+                  {
+                    dog {
+                      name
+                      doesKnowCommand(dogCommand: SIT)
+                    }
+                    dog {
+                      name
+                      doesKnowCommand: isHousetrained(atOtherHomes: true)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fields \"doesKnowCommand\" conflict because \
+                            \\"doesKnowCommand\" and \"isHousetrained\" are \
+                            \different fields. Use different aliases on the \
+                            \fields to fetch both if this was intentional."
+                        , locations = [AST.Location 5 23, AST.Location 9 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "possibleFragmentSpreadsRule" $ do
+            it "rejects object inline spreads outside object scope" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ... on Cat {
+                        meowVolume
+                      }
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment cannot be spread here as objects of type \
+                            \\"Dog\" can never be of type \"Cat\"."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "rejects object named spreads outside object scope" $
+                let queryString = [r|
+                  {
+                    dog {
+                      ... catInDogFragmentInvalid
+                    }
+                  }
+
+                  fragment catInDogFragmentInvalid on Cat {
+                    meowVolume
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Fragment \"catInDogFragmentInvalid\" cannot be \
+                            \spread here as objects of type \"Dog\" can never \
+                            \be of type \"Cat\"."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "providedRequiredInputFieldsRule" $
+            it "rejects missing required input fields" $
+                let queryString = [r|
+                  {
+                    findDog(complex: { name: null }) {
+                      name
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Input field \"name\" of type \"DogData\" is \
+                            \required, but it was not provided."
+                        , locations = [AST.Location 3 38]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "providedRequiredArgumentsRule" $
+            it "checks for (non-)nullable arguments" $
+                let queryString = [r|
+                  {
+                    dog {
+                      doesKnowCommand(dogCommand: null)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Field \"doesKnowCommand\" argument \"dogCommand\" \
+                            \of type \"DogCommand\" is required, but it was \
+                            \not provided."
+                        , locations = [AST.Location 4 23]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "variablesInAllowedPositionRule" $ do
+            it "rejects wrongly typed variable arguments" $
+                let queryString = [r|
+                  query catCommandArgQuery($catCommandArg: CatCommand) {
+                    cat {
+                      doesKnowCommand(catCommand: $catCommandArg)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Variable \"$catCommandArg\" of type \
+                            \\"CatCommand\" used in position expecting type \
+                            \\"!CatCommand\"."
+                        , locations = [AST.Location 2 44]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+            it "rejects wrongly typed variable arguments" $
+                let queryString = [r|
+                  query intCannotGoIntoBoolean($intArg: Int) {
+                    dog {
+                      isHousetrained(atOtherHomes: $intArg)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Variable \"$intArg\" of type \"Int\" used in \
+                            \position expecting type \"Boolean\"."
+                        , locations = [AST.Location 2 48]
+                        }
+                 in validate queryString `shouldBe` [expected]
+
+        context "valuesOfCorrectTypeRule" $
+            it "rejects values of incorrect types" $
+                let queryString = [r|
+                  {
+                    dog {
+                      isHousetrained(atOtherHomes: 3)
+                    }
+                  }
+                |]
+                    expected = Error
+                        { message =
+                            "Value 3 cannot be coerced to type \"Boolean\"."
+                        , locations = [AST.Location 4 52]
+                        }
+                 in validate queryString `shouldBe` [expected]

tests/Language/GraphQL/ValidateSpec.hs

@@ -1,665 +0,0 @@
-{- This Source Code Form is subject to the terms of the Mozilla Public License,
-   v. 2.0. If a copy of the MPL was not distributed with this file, You can
-   obtain one at https://mozilla.org/MPL/2.0/. -}
-
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE QuasiQuotes #-}
-
-module Language.GraphQL.ValidateSpec
-    ( spec
-    ) where
-
-import Data.Foldable (toList)
-import qualified Data.HashMap.Strict as HashMap
-import Data.Text (Text)
-import qualified Language.GraphQL.AST as AST
-import Language.GraphQL.Type
-import qualified Language.GraphQL.Type.In as In
-import qualified Language.GraphQL.Type.Out as Out
-import Language.GraphQL.Validate
-import Test.Hspec (Spec, describe, it, shouldBe, shouldContain)
-import Text.Megaparsec (parse)
-import Text.RawString.QQ (r)
-
-petSchema :: Schema IO
-petSchema = schema queryType Nothing (Just subscriptionType) mempty
-
-queryType :: ObjectType IO
-queryType = ObjectType "Query" Nothing [] $ HashMap.fromList
-    [ ("dog", dogResolver)
-    , ("findDog", findDogResolver)
-    ]
-  where
-    dogField = Field Nothing (Out.NamedObjectType dogType) mempty
-    dogResolver = ValueResolver dogField $ pure Null
-    findDogArguments = HashMap.singleton "complex"
-        $ In.Argument Nothing (In.NonNullInputObjectType dogDataType) Nothing
-    findDogField = Field Nothing (Out.NamedObjectType dogType) findDogArguments
-    findDogResolver = ValueResolver findDogField $ pure Null
-
-dogCommandType :: EnumType
-dogCommandType = EnumType "DogCommand" Nothing $ HashMap.fromList
-    [ ("SIT", EnumValue Nothing)
-    , ("DOWN", EnumValue Nothing)
-    , ("HEEL", EnumValue Nothing)
-    ]
-
-dogType :: ObjectType IO
-dogType = ObjectType "Dog" Nothing [petType] $ HashMap.fromList
-    [ ("name", nameResolver)
-    , ("nickname", nicknameResolver)
-    , ("barkVolume", barkVolumeResolver)
-    , ("doesKnowCommand", doesKnowCommandResolver)
-    , ("isHousetrained", isHousetrainedResolver)
-    , ("owner", ownerResolver)
-    ]
-  where
-    nameField = Field Nothing (Out.NonNullScalarType string) mempty
-    nameResolver = ValueResolver nameField $ pure "Name"
-    nicknameField = Field Nothing (Out.NamedScalarType string) mempty
-    nicknameResolver = ValueResolver nicknameField $ pure "Nickname"
-    barkVolumeField = Field Nothing (Out.NamedScalarType int) mempty
-    barkVolumeResolver = ValueResolver barkVolumeField $ pure $ Int 3
-    doesKnowCommandField = Field Nothing (Out.NonNullScalarType boolean)
-        $ HashMap.singleton "dogCommand"
-        $ In.Argument Nothing (In.NonNullEnumType dogCommandType) Nothing
-    doesKnowCommandResolver = ValueResolver doesKnowCommandField
-        $ pure $ Boolean True
-    isHousetrainedField = Field Nothing (Out.NonNullScalarType boolean)
-        $ HashMap.singleton "atOtherHomes"
-        $ In.Argument Nothing (In.NamedScalarType boolean) Nothing
-    isHousetrainedResolver = ValueResolver isHousetrainedField
-        $ pure $ Boolean True
-    ownerField = Field Nothing (Out.NamedObjectType humanType) mempty
-    ownerResolver = ValueResolver ownerField $ pure Null
-
-dogDataType :: InputObjectType
-dogDataType = InputObjectType "DogData" Nothing
-    $ HashMap.singleton "name" nameInputField
-  where
-    nameInputField = InputField Nothing (In.NonNullScalarType string) Nothing
-
-sentientType :: InterfaceType IO
-sentientType = InterfaceType "Sentient" Nothing []
-    $ HashMap.singleton "name"
-    $ Field Nothing (Out.NonNullScalarType string) mempty
-
-petType :: InterfaceType IO
-petType = InterfaceType "Pet" Nothing []
-    $ HashMap.singleton "name"
-    $ Field Nothing (Out.NonNullScalarType string) mempty
-
-subscriptionType :: ObjectType IO
-subscriptionType = ObjectType "Subscription" Nothing [] $ HashMap.fromList
-    [ ("newMessage", newMessageResolver)
-    , ("disallowedSecondRootField", newMessageResolver)
-    ]
-  where
-    newMessageField = Field Nothing (Out.NonNullObjectType messageType) mempty
-    newMessageResolver = ValueResolver newMessageField
-        $ pure $ Object HashMap.empty
-
-messageType :: ObjectType IO
-messageType = ObjectType "Message" Nothing [] $ HashMap.fromList
-    [ ("sender", senderResolver)
-    , ("body", bodyResolver)
-    ]
-  where
-    senderField = Field Nothing (Out.NonNullScalarType string) mempty
-    senderResolver = ValueResolver senderField $ pure "Sender"
-    bodyField = Field Nothing (Out.NonNullScalarType string) mempty
-    bodyResolver = ValueResolver bodyField $ pure "Message body."
-
-humanType :: ObjectType IO
-humanType = ObjectType "Human" Nothing [sentientType] $ HashMap.fromList
-    [ ("name", nameResolver)
-    , ("pets", petsResolver)
-    ]
-  where
-    nameField = Field Nothing (Out.NonNullScalarType string) mempty
-    nameResolver = ValueResolver nameField $ pure "Name"
-    petsField =
-        Field Nothing (Out.ListType $ Out.NonNullInterfaceType petType) mempty
-    petsResolver = ValueResolver petsField $ pure $ List []
-{-
-catOrDogType :: UnionType IO
-catOrDogType = UnionType "CatOrDog" Nothing [catType, dogType]
--}
-validate :: Text -> [Error]
-validate queryString =
-    case parse AST.document "" queryString of
-        Left _ -> []
-        Right ast -> toList $ document petSchema specifiedRules ast
-
-spec :: Spec
-spec =
-    describe "document" $ do
-        it "rejects type definitions" $
-            let queryString = [r|
-              query getDogName {
-                dog {
-                  name
-                  color
-                }
-              }
-
-              extend type Dog {
-                color: String
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Definition must be OperationDefinition or FragmentDefinition."
-                    , locations = [AST.Location 9 15]
-                    }
-               in validate queryString `shouldContain` [expected]
-
-        it "rejects multiple subscription root fields" $
-            let queryString = [r|
-              subscription sub {
-                newMessage {
-                  body
-                  sender
-                }
-                disallowedSecondRootField
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Subscription \"sub\" must select only one top level \
-                        \field."
-                    , locations = [AST.Location 2 15]
-                    }
-             in validate queryString `shouldContain` [expected]
-
-        it "rejects multiple subscription root fields coming from a fragment" $
-            let queryString = [r|
-              subscription sub {
-                ...multipleSubscriptions
-              }
-
-              fragment multipleSubscriptions on Subscription {
-                newMessage {
-                  body
-                  sender
-                }
-                disallowedSecondRootField
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Subscription \"sub\" must select only one top level \
-                        \field."
-                    , locations = [AST.Location 2 15]
-                    }
-             in validate queryString `shouldContain` [expected]
-
-        it "rejects multiple anonymous operations" $
-            let queryString = [r|
-              {
-                dog {
-                  name
-                }
-              }
-
-              query getName {
-                dog {
-                  owner {
-                    name
-                  }
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "This anonymous operation must be the only defined operation."
-                    , locations = [AST.Location 2 15]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects operations with the same name" $
-            let queryString = [r|
-              query dogOperation {
-                dog {
-                  name
-                }
-              }
-
-              mutation dogOperation {
-                mutateDog {
-                  id
-                }
-            }
-            |]
-                expected = Error
-                    { message =
-                        "There can be only one operation named \"dogOperation\"."
-                    , locations = [AST.Location 2 15, AST.Location 8 15]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects fragments with the same name" $
-            let queryString = [r|
-              {
-                dog {
-                  ...fragmentOne
-                }
-              }
-
-              fragment fragmentOne on Dog {
-                name
-              }
-
-              fragment fragmentOne on Dog {
-                owner {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "There can be only one fragment named \"fragmentOne\"."
-                    , locations = [AST.Location 8 15, AST.Location 12 15]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects the fragment spread without a target" $
-            let queryString = [r|
-              {
-                dog {
-                  ...undefinedFragment
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Fragment target \"undefinedFragment\" is undefined."
-                    , locations = [AST.Location 4 19]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects fragment spreads without an unknown target type" $
-            let queryString = [r|
-              {
-                dog {
-                  ...notOnExistingType
-                }
-              }
-              fragment notOnExistingType on NotInSchema {
-                name
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Fragment \"notOnExistingType\" is specified on type \
-                        \\"NotInSchema\" which doesn't exist in the schema."
-                    , locations = [AST.Location 4 19]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects inline fragments without a target" $
-            let queryString = [r|
-              {
-                ... on NotInSchema {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Inline fragment is specified on type \"NotInSchema\" \
-                        \which doesn't exist in the schema."
-                    , locations = [AST.Location 3 17]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects fragments on scalar types" $
-            let queryString = [r|
-              {
-                dog {
-                  ...fragOnScalar
-                }
-              }
-              fragment fragOnScalar on Int {
-                name
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Fragment cannot condition on non composite type \
-                        \\"Int\"."
-                    , locations = [AST.Location 7 15]
-                    }
-             in validate queryString `shouldContain` [expected]
-
-        it "rejects inline fragments on scalar types" $
-            let queryString = [r|
-              {
-                ... on Boolean {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Fragment cannot condition on non composite type \
-                        \\"Boolean\"."
-                    , locations = [AST.Location 3 17]
-                    }
-             in validate queryString `shouldContain` [expected]
-
-        it "rejects unused fragments" $
-            let queryString = [r|
-              fragment nameFragment on Dog { # unused
-                name
-              }
-
-              {
-                dog {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Fragment \"nameFragment\" is never used."
-                    , locations = [AST.Location 2 15]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects spreads that form cycles" $
-            let queryString = [r|
-              {
-                dog {
-                  ...nameFragment
-                }
-              }
-              fragment nameFragment on Dog {
-                name
-                ...barkVolumeFragment
-              }
-              fragment barkVolumeFragment on Dog {
-                barkVolume
-                ...nameFragment
-              }
-            |]
-                error1 = Error
-                    { message =
-                        "Cannot spread fragment \"barkVolumeFragment\" within \
-                        \itself (via barkVolumeFragment -> nameFragment -> \
-                        \barkVolumeFragment)."
-                    , locations = [AST.Location 11 15]
-                    }
-                error2 = Error
-                    { message =
-                        "Cannot spread fragment \"nameFragment\" within itself \
-                        \(via nameFragment -> barkVolumeFragment -> \
-                        \nameFragment)."
-                    , locations = [AST.Location 7 15]
-                    }
-             in validate queryString `shouldBe` [error1, error2]
-
-        it "rejects duplicate field arguments" $ do
-            let queryString = [r|
-              {
-                dog {
-                  isHousetrained(atOtherHomes: true, atOtherHomes: true)
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "There can be only one argument named \"atOtherHomes\"."
-                    , locations = [AST.Location 4 34, AST.Location 4 54]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects more than one directive per location" $ do
-            let queryString = [r|
-              query ($foo: Boolean = true, $bar: Boolean = false) {
-                dog @skip(if: $foo) @skip(if: $bar) {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "There can be only one directive named \"skip\"."
-                    , locations = [AST.Location 3 21, AST.Location 3 37]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects duplicate variables" $
-            let queryString = [r|
-              query houseTrainedQuery($atOtherHomes: Boolean, $atOtherHomes: Boolean) {
-                dog {
-                  isHousetrained(atOtherHomes: $atOtherHomes)
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "There can be only one variable named \"atOtherHomes\"."
-                    , locations = [AST.Location 2 39, AST.Location 2 63]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects non-input types as variables" $
-            let queryString = [r|
-              query takesDogBang($dog: Dog!) {
-                dog {
-                  isHousetrained(atOtherHomes: $dog)
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Variable \"$dog\" cannot be non-input type \"Dog\"."
-                    , locations = [AST.Location 2 34]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects undefined variables" $
-            let queryString = [r|
-              query variableIsNotDefinedUsedInSingleFragment {
-                dog {
-                  ...isHousetrainedFragment
-                }
-              }
-
-              fragment isHousetrainedFragment on Dog {
-                isHousetrained(atOtherHomes: $atOtherHomes)
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Variable \"$atOtherHomes\" is not defined by \
-                        \operation \
-                        \\"variableIsNotDefinedUsedInSingleFragment\"."
-                    , locations = [AST.Location 9 46]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects unused variables" $
-            let queryString = [r|
-              query variableUnused($atOtherHomes: Boolean) {
-                dog {
-                  isHousetrained
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Variable \"$atOtherHomes\" is never used in operation \
-                        \\"variableUnused\"."
-                    , locations = [AST.Location 2 36]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects duplicate fields in input objects" $
-            let queryString = [r|
-              {
-                findDog(complex: { name: "Fido", name: "Jack" }) {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "There can be only one input field named \"name\"."
-                    , locations = [AST.Location 3 36, AST.Location 3 50]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects undefined fields" $
-            let queryString = [r|
-              {
-                dog {
-                  meowVolume
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Cannot query field \"meowVolume\" on type \"Dog\"."
-                    , locations = [AST.Location 4 19]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects scalar fields with not empty selection set" $
-            let queryString = [r|
-              {
-                dog {
-                  barkVolume {
-                    sinceWhen
-                  }
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Field \"barkVolume\" must not have a selection since \
-                        \type \"Int\" has no subfields."
-                    , locations = [AST.Location 4 19]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects field arguments missing in the type" $
-            let queryString = [r|
-              {
-                dog {
-                  doesKnowCommand(command: CLEAN_UP_HOUSE, dogCommand: SIT)
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Unknown argument \"command\" on field \
-                        \\"Dog.doesKnowCommand\"."
-                    , locations = [AST.Location 4 35]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects directive arguments missing in the definition" $
-            let queryString = [r|
-              {
-                dog {
-                  isHousetrained(atOtherHomes: true) @include(unless: false, if: true)
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Unknown argument \"unless\" on directive \"@include\"."
-                    , locations = [AST.Location 4 63]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects undefined directives" $
-            let queryString = [r|
-              {
-                dog {
-                  isHousetrained(atOtherHomes: true) @ignore(if: true)
-                }
-              }
-            |]
-                expected = Error
-                    { message = "Unknown directive \"@ignore\"."
-                    , locations = [AST.Location 4 54]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects undefined input object fields" $
-            let queryString = [r|
-              {
-                findDog(complex: { favoriteCookieFlavor: "Bacon", name: "Jack" }) {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Field \"favoriteCookieFlavor\" is not defined \
-                        \by type \"DogData\"."
-                    , locations = [AST.Location 3 36]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects directives in invalid locations" $
-            let queryString = [r|
-              query @skip(if: $foo) {
-                dog {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message = "Directive \"@skip\" may not be used on QUERY."
-                    , locations = [AST.Location 2 21]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "rejects missing required input fields" $
-            let queryString = [r|
-              {
-                findDog(complex: { name: null }) {
-                  name
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Input field \"name\" of type \"DogData\" is required, \
-                        \but it was not provided."
-                    , locations = [AST.Location 3 34]
-                    }
-             in validate queryString `shouldBe` [expected]
-
-        it "finds corresponding subscription fragment" $
-            let queryString = [r|
-              subscription sub {
-                ...anotherSubscription
-                ...multipleSubscriptions
-              }
-              fragment multipleSubscriptions on Subscription {
-                newMessage {
-                  body
-                }
-                disallowedSecondRootField {
-                  sender
-                }
-              }
-              fragment anotherSubscription on Subscription {
-                newMessage {
-                  body
-                  sender
-                }
-              }
-            |]
-                expected = Error
-                    { message =
-                        "Subscription \"sub\" must select only one top level \
-                        \field."
-                    , locations = [AST.Location 2 15]
-                    }
-             in validate queryString `shouldBe` [expected]