Add String instances from ToGraphQL and FromGraphQL

For deriving FromGraphQL instances automatically.

.gitea/deploy.awk

@@ -0,0 +1,3 @@
+END {
+    system("cabal upload --username belka --password "ENVIRON["HACKAGE_PASSWORD"]" "$0)
+}

.gitea/workflows/build.yml

@@ -0,0 +1,33 @@
+name: Build
+
+on:
+  push:
+    branches:
+      - '**'
+  pull_request:
+    branches: [master]
+
+jobs:
+  audit:
+    runs-on: buildenv
+    steps:
+      - uses: actions/checkout@v4
+      - run: hlint -- src tests
+
+  test:
+    runs-on: buildenv
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install dependencies
+        run: cabal update
+      - name: Prepare system
+        run: cabal build graphql-test
+      - run: cabal test --test-show-details=streaming
+
+  doc:
+    runs-on: buildenv
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install dependencies
+        run: cabal update
+      - run: cabal haddock --enable-documentation

.gitea/workflows/release.yml

@@ -0,0 +1,17 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - '**'
+
+jobs:
+  release:
+    runs-on: buildenv
+    steps:
+      - uses: actions/checkout@v4
+      - name: Upload a candidate
+        env:
+          HACKAGE_PASSWORD: ${{ secrets.HACKAGE_PASSWORD }}
+        run: |
+          cabal sdist | awk -f .gitea/deploy.awk

CHANGELOG.md

@@ -6,6 +6,43 @@ The format is based on
 and this project adheres to
 [Haskell Package Versioning Policy](https://pvp.haskell.org/).
 
+## [Unreleased]
+### Removed
+- Deprecated `Language.GraphQL.Class.gql` (moved to `Language.GraphQL.TH`).
+
+### Added
+- `String` instances from `ToGraphQL` and `FromGraphQL`.
+
+## [1.0.6.0] - 2024-12-06
+### Added
+- `Language.GraphQL.Class.gql` is moved to `Language.GraphQL.TH` where it was
+  before in `graphql`.
+
+## [1.0.5.0] - 2024-11-21
+### Added
+- Add `ToGraphQL` and `FromGraphQL` instances for `Value` and `HashMap`.
+
+## [1.0.4.0] - 2024-10-24
+### Added
+- `gql` quasi quoter which generates a string literal with the first line
+  starting at the first column and all following lines indented relative to the
+  first line.
+
+## [1.0.3.0] - 2024-07-20
+### Added
+- Add `deriveToGraphQL` for deriving `ToGraphQL` instances automatically.
+- Add `deriveFromGraphQL`for deriving `FromGraphQL` instances automatically.
+
+## [1.0.2.0] - 2023-07-07
+### Added
+- `ToGraphQL` and `FromGraphQL` instances for `Word` types, `Float`, `Double`,
+  and `Scientific`.
+- `ToGraphQL` and `FromGraphQL` instances for `Day`, `DiffTime`,
+  `NominalDiffTime`, `UTCTime`, `LocalTime` and `TimeOfDay`.
+- `Resolver`: Export `ServerException`.
+- `Resolver.defaultResolver`: Throw `FieldNotResolvedException` if the requested
+  field is not in the parent object.
+
 ## [1.0.1.0] - 2023-02-17
 ### Added
 - `ToGraphQL` and `FromGraphQL` typeclasses with instances for basic types.
@@ -16,4 +53,10 @@ and this project adheres to
 - JSON serialization.
 - Test helpers.
 
-[1.0.1.0]: https://www.caraus.tech/projects/pub-graphql-spice/repository/28/diff?rev=v1.0.1.0&rev_to=v1.0.0.0
+[Unreleased]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.6.0...master
+[1.0.6.0]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.5.0...v1.0.6.0
+[1.0.5.0]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.4.0...v1.0.5.0
+[1.0.4.0]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.3.0...v1.0.4.0
+[1.0.3.0]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.2.0...v1.0.3.0
+[1.0.2.0]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.1.0...v1.0.2.0
+[1.0.1.0]: https://git.caraus.tech/OSS/graphql-spice/compare/v1.0.0.0...v1.0.1.0

cabal.project

@@ -1,4 +0,0 @@
-packages:
-  .
-
-constraints: graphql -json

graphql-spice.cabal

@@ -1,49 +1,52 @@
-cabal-version:      2.4
+cabal-version:      3.0
 
 name:               graphql-spice
-version:            1.0.1.0
+version:            1.0.6.0
 synopsis:           GraphQL with batteries
-description:        Various extensions and convenience functions  for the core
+description:        Various extensions and convenience functions for the core
                     graphql package.
 category:           Language
-homepage:           https://www.caraus.tech/projects/pub-graphql-spice
-bug-reports:        https://www.caraus.tech/projects/pub-graphql-spice/issues
+homepage:           https://git.caraus.tech/OSS/graphql-spice
+bug-reports:        https://git.caraus.tech/OSS/graphql-spice/issues
 author:             Eugen Wissner <belka@caraus.de>
 maintainer:         belka@caraus.de
-copyright:          (c) 2021-2023 Eugen Wissner
+copyright:          (c) 2021-2024 Eugen Wissner
 license:            MPL-2.0
 license-files:      LICENSE
 build-type:         Simple
 extra-source-files: CHANGELOG.md
 tested-with:
-  GHC == 9.2.5
+  GHC == 9.8.2
 
 source-repository head
   type: git
-  location: git://caraus.tech/pub/graphql-spice.git
+  location: https://git.caraus.tech/OSS/graphql-spice.git
 
 library
     exposed-modules:
       Language.GraphQL.Class
       Language.GraphQL.JSON
       Language.GraphQL.Resolver
+      Language.GraphQL.TH
       Test.Hspec.GraphQL
     other-modules:
     hs-source-dirs:   src
     ghc-options: -Wall
     build-depends:
-      aeson ^>= 2.0.3,
+      aeson >= 2.0.3 && < 2.3,
       base >= 4.7 && < 5,
       conduit ^>= 1.3.4,
-      containers ^>= 0.6.2,
+      containers >= 0.6 && < 0.8,
       exceptions ^>= 0.10.4,
       hspec-expectations >= 0.8.2 && < 0.9,
-      graphql >= 1.0,
+      graphql ^>= 1.5.0,
       megaparsec >= 9.0 && < 10,
       scientific ^>= 0.3.7,
+      template-haskell >= 2.16 && < 3,
       text >= 1.2 && < 3,
-      transformers ^>= 0.5.6,
-      vector ^>= 0.12.3,
+      time >= 1.12.2 && < 1.15,
+      transformers >= 0.5.6 && < 0.7,
+      vector >= 0.12 && < 0.14,
       unordered-containers ^>= 0.2.16
     default-language: Haskell2010
 
@@ -56,6 +59,7 @@ test-suite graphql-test
     Language.GraphQL.DirectiveSpec
     Language.GraphQL.FragmentSpec
     Language.GraphQL.RootOperationSpec
+    Language.GraphQL.THSpec
   hs-source-dirs:
     tests
   ghc-options: -threaded -rtsopts -with-rtsopts=-N -Wall
@@ -67,5 +71,8 @@ test-suite graphql-test
     hspec >= 2.9.1 && < 3,
     scientific,
     text,
+    time,
     unordered-containers
+  build-tool-depends:
+    hspec-discover:hspec-discover
   default-language: Haskell2010

src/Language/GraphQL/Class.hs

@@ -3,21 +3,80 @@
    obtain one at https://mozilla.org/MPL/2.0/. -}
 
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TupleSections #-}
+{-# LANGUAGE FlexibleInstances #-}
 
 -- | ToGraphQL and FromGraphQL typeclasses used for user-defined type
 -- conversion.
 module Language.GraphQL.Class
     ( FromGraphQL(..)
     , ToGraphQL(..)
+    , deriveFromGraphQL
+    , deriveToGraphQL
     ) where
 
-import Data.Foldable (toList)
 import Data.Int (Int8, Int16, Int32, Int64)
 import Data.Text (Text)
+import Data.Word (Word8, Word16, Word32, Word64)
 import qualified Data.Text.Read as Text.Read
 import Data.Vector (Vector)
 import qualified Data.Vector as Vector
+import Data.Scientific (Scientific, toRealFloat)
+import qualified Data.Text as Text
+import Data.Time
+    ( Day
+    , DiffTime
+    , LocalTime(..)
+    , NominalDiffTime
+    , TimeOfDay(..)
+    , UTCTime(..)
+    , showGregorian
+    , secondsToNominalDiffTime
+    , secondsToDiffTime
+    )
+import Data.Time.Format.ISO8601
+    ( ISO8601(..)
+    , formatParseM
+    , iso8601Format
+    , iso8601Show
+    )
+import Language.Haskell.TH
+    ( Con(..)
+    , Dec(..)
+    , Exp(..)
+    , Info(..)
+    , Quote(..)
+    , Name
+    , Q
+    , VarBangType
+    , appT
+    , conP
+    , conT
+    , instanceD
+    , recP
+    , reify
+    , nameBase
+    , listE
+    , stringL
+    , tupE
+    , litE
+    , varE
+    , varP
+    , funD
+    , clause
+    , normalB
+    , appE
+    , mkName
+    , conE
+    , integerL
+    , litP
+    , wildP
+    )
+import Data.Foldable (Foldable(..))
+import qualified Data.HashMap.Strict as HashMap
 import qualified Language.GraphQL.Type as Type
+import Prelude hiding (id)
 
 fromGraphQLToIntegral :: Integral a => Type.Value -> Maybe a
 fromGraphQLToIntegral (Type.Int value) = Just $ fromIntegral value
@@ -27,79 +86,382 @@ fromGraphQLToIntegral (Type.String value) =
         _conversionError -> Nothing
 fromGraphQLToIntegral _ = Nothing
 
+iso8601ToGraphQL :: ISO8601 t => t -> Type.Value
+iso8601ToGraphQL = Type.String . Text.pack . iso8601Show
+
+fromGraphQLToISO8601 :: ISO8601 t => Type.Value -> Maybe t
+fromGraphQLToISO8601 (Type.String value') = formatParseM iso8601Format $ Text.unpack value'
+fromGraphQLToISO8601 _ = Nothing
+
 -- | Instances of this typeclass can be converted to GraphQL internal
 -- representation.
-class ToGraphQL a where
+class ToGraphQL a
+  where
     toGraphQL :: a -> Type.Value
 
-instance ToGraphQL Text where
+instance ToGraphQL Type.Value
+  where
+    toGraphQL a = a
+
+instance ToGraphQL Text
+  where
     toGraphQL = Type.String
 
-instance ToGraphQL Int where
+instance ToGraphQL String
+  where
+    toGraphQL = Type.String . Text.pack
+
+instance ToGraphQL Int
+  where
     toGraphQL = Type.Int . fromIntegral
 
-instance ToGraphQL Int8 where
+instance ToGraphQL Int8
+  where
     toGraphQL = Type.Int . fromIntegral
 
-instance ToGraphQL Int16 where
+instance ToGraphQL Int16
+  where
     toGraphQL = Type.Int . fromIntegral
 
-instance ToGraphQL Int32 where
+instance ToGraphQL Int32
+  where
     toGraphQL = Type.Int
 
-instance ToGraphQL Int64 where
+instance ToGraphQL Int64
+  where
     toGraphQL = Type.Int . fromIntegral
 
-instance ToGraphQL a => ToGraphQL [a] where
+instance ToGraphQL Word
+  where
+    toGraphQL = Type.Int . fromIntegral
+
+instance ToGraphQL Word8
+  where
+    toGraphQL = Type.Int . fromIntegral
+
+instance ToGraphQL Word16
+  where
+    toGraphQL = Type.Int . fromIntegral
+
+instance ToGraphQL Word32
+  where
+    toGraphQL = Type.Int . fromIntegral
+
+instance ToGraphQL Word64
+  where
+    toGraphQL = Type.Int . fromIntegral
+
+instance ToGraphQL a => ToGraphQL [a]
+  where
     toGraphQL = Type.List . fmap toGraphQL
 
-instance ToGraphQL a => ToGraphQL (Vector a) where
+instance ToGraphQL a => ToGraphQL (Vector a)
+  where
     toGraphQL = Type.List . toList . fmap toGraphQL
 
-instance ToGraphQL a => ToGraphQL (Maybe a) where
+instance ToGraphQL a => ToGraphQL (Maybe a)
+  where
     toGraphQL (Just justValue) = toGraphQL justValue
     toGraphQL Nothing = Type.Null
 
-instance ToGraphQL Bool where
+instance ToGraphQL Bool
+  where
     toGraphQL = Type.Boolean
 
+instance ToGraphQL Float
+  where
+    toGraphQL = Type.Float . realToFrac
+
+instance ToGraphQL Double
+  where
+    toGraphQL = Type.Float
+
+instance ToGraphQL Scientific
+  where
+    toGraphQL = Type.Float . toRealFloat
+
+instance ToGraphQL Day
+  where
+    toGraphQL = Type.String . Text.pack . showGregorian
+
+instance ToGraphQL DiffTime
+  where
+    toGraphQL = Type.Int . truncate . (realToFrac :: DiffTime -> Double)
+
+instance ToGraphQL NominalDiffTime
+  where
+    toGraphQL = Type.Int . truncate . (realToFrac :: NominalDiffTime -> Double)
+
+instance ToGraphQL UTCTime
+  where
+    toGraphQL = iso8601ToGraphQL
+
+instance ToGraphQL TimeOfDay
+  where
+    toGraphQL = iso8601ToGraphQL
+
+instance ToGraphQL LocalTime
+  where
+    toGraphQL = iso8601ToGraphQL
+
+instance ToGraphQL a => ToGraphQL (HashMap.HashMap Text a)
+  where
+    toGraphQL = Type.Object . fmap toGraphQL
+
 -- | Instances of this typeclass can be used to convert GraphQL internal
 -- representation to user-defined type.
-class FromGraphQL a where
+class FromGraphQL a
+  where
     fromGraphQL :: Type.Value -> Maybe a
 
-instance FromGraphQL Text where
+instance FromGraphQL Type.Value
+  where
+    fromGraphQL = Just
+
+instance FromGraphQL Text
+  where
     fromGraphQL (Type.String value) = Just value
     fromGraphQL _ = Nothing
 
-instance FromGraphQL Int where
+instance FromGraphQL String
+  where
+    fromGraphQL (Type.String value) = Just $ Text.unpack value
+    fromGraphQL _ = Nothing
+
+instance FromGraphQL Int
+  where
     fromGraphQL = fromGraphQLToIntegral
 
-instance FromGraphQL Int8 where
+instance FromGraphQL Int8
+  where
     fromGraphQL = fromGraphQLToIntegral
 
-instance FromGraphQL Int16 where
+instance FromGraphQL Int16
+  where
     fromGraphQL = fromGraphQLToIntegral
 
-instance FromGraphQL Int32 where
+instance FromGraphQL Int32
+  where
     fromGraphQL = fromGraphQLToIntegral
 
-instance FromGraphQL Int64 where
+instance FromGraphQL Int64
+  where
     fromGraphQL = fromGraphQLToIntegral
 
-instance FromGraphQL a => FromGraphQL [a] where
+instance FromGraphQL Word
+  where
+    fromGraphQL = fromGraphQLToIntegral
+
+instance FromGraphQL Word8
+  where
+    fromGraphQL = fromGraphQLToIntegral
+
+instance FromGraphQL Word16
+  where
+    fromGraphQL = fromGraphQLToIntegral
+
+instance FromGraphQL Word32
+  where
+    fromGraphQL = fromGraphQLToIntegral
+
+instance FromGraphQL Word64
+  where
+    fromGraphQL = fromGraphQLToIntegral
+
+instance FromGraphQL a => FromGraphQL [a]
+  where
     fromGraphQL (Type.List value) = traverse fromGraphQL value
     fromGraphQL _ = Nothing
 
-instance FromGraphQL a => FromGraphQL (Vector a) where
+instance FromGraphQL a => FromGraphQL (Vector a)
+  where
     fromGraphQL (Type.List value) = Vector.fromList
         <$> traverse fromGraphQL value
     fromGraphQL _ = Nothing
 
-instance FromGraphQL a => FromGraphQL (Maybe a) where
+instance FromGraphQL a => FromGraphQL (Maybe a)
+  where
     fromGraphQL Type.Null = Just Nothing
     fromGraphQL value = Just <$> fromGraphQL value
 
-instance FromGraphQL Bool where
+instance FromGraphQL Bool
+  where
     fromGraphQL (Type.Boolean value) = Just value
     fromGraphQL _ = Nothing
+
+instance FromGraphQL Float
+  where
+    fromGraphQL (Type.Float value) = Just $ realToFrac value
+    fromGraphQL _ = Nothing
+
+instance FromGraphQL Double
+  where
+    fromGraphQL (Type.Float value) = Just value
+    fromGraphQL _ = Nothing
+
+instance FromGraphQL Scientific
+  where
+    fromGraphQL (Type.Float value) = Just $ realToFrac value
+    fromGraphQL _ = Nothing
+
+instance FromGraphQL Day
+  where
+    fromGraphQL = fromGraphQLToISO8601
+
+instance FromGraphQL DiffTime
+  where
+    fromGraphQL (Type.Int value') = Just $ secondsToDiffTime $ fromIntegral value'
+    fromGraphQL _ = Nothing
+
+instance FromGraphQL NominalDiffTime
+  where
+    fromGraphQL (Type.Int value') = Just $ secondsToNominalDiffTime $ fromIntegral value'
+    fromGraphQL _ = Nothing
+
+instance FromGraphQL UTCTime
+  where
+    fromGraphQL = fromGraphQLToISO8601
+
+instance FromGraphQL TimeOfDay
+  where
+    fromGraphQL = fromGraphQLToISO8601
+
+instance FromGraphQL LocalTime
+  where
+    fromGraphQL = fromGraphQLToISO8601
+
+instance FromGraphQL a => FromGraphQL (HashMap.HashMap Text a)
+  where
+    fromGraphQL (Type.Object hm) = traverse fromGraphQL hm
+    fromGraphQL _ = Nothing
+
+stringLE :: Name -> Q Exp
+stringLE = litE . stringL . nameBase
+
+-- | Given a type derives a 'FromGraphQL' instance for it.
+--
+-- The derivation can only work when all nested types already have 'FromGraphQL'
+-- instances.
+--
+-- The following cases are supported:
+--
+-- * Records encode input objects.
+-- * Sum types with all data constructors without parameters encode Enums.
+deriveFromGraphQL :: Name -> Q [Dec]
+deriveFromGraphQL typeName = do
+    TyConI plainConstructor <- reify typeName
+    case plainConstructor of
+        DataD _ _ _ _ [cons'] _
+            | RecC dataConName varBangTypes <- cons' ->
+                withRecordConstructor dataConName varBangTypes
+        DataD _ _ _ _ cons' _ -> pure <$> generateEnumInstance cons'
+        NewtypeD _ _ _ _ cons' _
+            | RecC dataConName varBangTypes <- cons' ->
+                withRecordConstructor dataConName varBangTypes
+        _ -> error "Only input objects and enums are supported if all member types have a FromGraphQL instance"
+  where
+    enumMemberPattern (NormalC normalName []) =
+        let fromGraphQLF = conP (mkName "Type.Enum") [litP $ stringL $ nameBase normalName]
+         in flip (clause [fromGraphQLF]) []
+            $ normalB [|Just $(conE normalName)|]
+    enumMemberPattern _ =
+        error "Enum member should be a normal constructor without parameters"
+    generateEnumInstance :: [Con] -> Q Dec
+    generateEnumInstance cons'
+        = instanceD mempty (appT (conT ''FromGraphQL) conTName)
+        $ pure $ funD 'fromGraphQL
+        $ (enumMemberPattern <$> cons')
+        <> [clause [wildP] (normalB [|Nothing|]) []]
+    hashMapLookup fieldName objectName =
+        [|HashMap.lookup $(stringLE fieldName) $objectName >>= fromGraphQL|]
+    addRecordField objectName accumulator (name', _, _)
+        = appE (appE (varE $ mkName "<*>") accumulator)
+        $ hashMapLookup name' objectName
+    withRecordConstructor dataConName varBangTypes = do
+        valueName <- newName "value"
+        let objectName = varE valueName
+            toGraphQLF = conP (mkName "Type.Object") [varP valueName]
+            fBody = makeRecordBody (conE dataConName) objectName varBangTypes
+            recordSize = litE $ integerL $ fromIntegral $ length varBangTypes
+        [d|
+            instance FromGraphQL $conTName
+              where
+                fromGraphQL $toGraphQLF
+                    | HashMap.size $objectName == $recordSize = $fBody
+                    | otherwise = Nothing
+                fromGraphQL _ = Nothing
+         |]
+    makeRecordBody dataConE objectName ((headName, _, _) : varBangTypes') =
+        let initialExpression = appE (appE (varE $ mkName "<$>") dataConE)
+                $ hashMapLookup headName objectName
+         in foldl' (addRecordField objectName) initialExpression varBangTypes'
+    makeRecordBody dataConE _ [] = dataConE
+    conTName = conT typeName
+
+-- | Given a type derives a 'ToGraphQL' instance for it.
+--
+-- The derivation can only work when all nested types already have 'ToGraphQL'
+-- instances.
+--
+-- The following cases are supported:
+--
+-- * Records are decoded as objects.
+-- * Sum types with all data constructors without parameters are decoded as Enums.
+-- * Sum types whose data constructors have exactly one parameter are decoded as Unions.
+deriveToGraphQL :: Name -> Q [Dec]
+deriveToGraphQL typeName = do
+    TyConI plainConstructor <- reify typeName
+    case plainConstructor of
+        DataD _ _ _ _ [cons'] _
+            | RecC dataConName varBangTypes <- cons' ->
+                withRecordConstructor dataConName varBangTypes
+        DataD _ _ _ _ cons' _ -> fmap pure
+            $ instanceD mempty (appT (conT ''ToGraphQL) conTName)
+            $ pure $ funD 'toGraphQL
+            $ generateSumTypeInstance cons'
+        NewtypeD _ _ _ _ cons' _
+            | RecC dataConName varBangTypes <- cons' ->
+                withRecordConstructor dataConName varBangTypes
+        _ -> error "Only objects, unions and enums are supported if all member types have a ToGraphQL instance"
+  where
+    conTName = conT typeName
+    collectEnumMemberNames (NormalC normalName []) = Just normalName
+    collectEnumMemberNames _ = Nothing
+    collectUnionMembers (NormalC normalName [_]) = Just normalName
+    collectUnionMembers _ = Nothing
+    enumMemberPattern normalName
+        = flip (clause [conP normalName mempty]) []
+        $ normalB [|Type.Enum $(stringLE normalName)|]
+    unionMemberPattern normalName = do
+        dataName <- newName "member"
+        flip (clause [conP normalName [varP dataName]]) []
+            $ normalB
+            $ appE (varE $ mkName "toGraphQL")
+            $ varE dataName
+    generateSumTypeInstance cons'
+        | Just enumMemberNames <- traverse collectEnumMemberNames cons' =
+            enumMemberPattern <$> enumMemberNames
+        | Just unionMembers <- traverse collectUnionMembers cons' =
+            unionMemberPattern <$> unionMembers
+        | otherwise =  error "All data constructors should have either no parameters (Enum) or one parameter (Union)"
+    withRecordConstructor dataConName varBangTypes = do
+        fieldAliases <- traverse newFieldAliases varBangTypes
+        let fBody =
+                [| Type.Object
+                    $ HashMap.insert "__typename" $(stringLE typeName)
+                    $ HashMap.fromList $(listE $ resultObjectPairs <$> fieldAliases)
+                |]
+            toGraphQLF = recP dataConName (newFieldPatterns <$> fieldAliases)
+        [d|
+            instance ToGraphQL $conTName
+              where
+                toGraphQL $toGraphQLF = $fBody
+         |]
+    newFieldAliases :: VarBangType -> Q (Name, Name)
+    newFieldAliases (name', _, _) = (name',) <$> newName (nameBase name')
+    newFieldPatterns (name', alias) = (name',) <$> varP alias
+    resultObjectPairs :: (Name, Name) -> Q Exp
+    resultObjectPairs (name', alias) = tupE
+        [ litE (stringL $ nameBase name')
+        , [|toGraphQL $(varE alias)|]
+        ]

src/Language/GraphQL/Resolver.hs

@@ -6,13 +6,14 @@
 
 -- | Helper functions and exceptions to write resolvers.
 module Language.GraphQL.Resolver
-    ( argument
+    ( ServerException(..)
+    , argument
     , defaultResolver
     ) where
 
 import Control.Monad.Catch (Exception(..), MonadCatch(..), MonadThrow(..))
 import Control.Monad.Trans.Reader (ReaderT, asks)
-import Data.HashMap.Strict ((!))
+import qualified Data.HashMap.Strict as HashMap
 import Data.Text (Text)
 import qualified Data.Text as Text
 import Data.Typeable (cast)
@@ -49,7 +50,8 @@ defaultResolver :: MonadCatch m => Name -> Type.Resolve m
 defaultResolver fieldName = do
     values' <- asks Type.values
     case values' of
-        Type.Object objectValue -> pure $ objectValue ! fieldName
+        Type.Object objectValue
+            | Just result <- HashMap.lookup fieldName objectValue -> pure result
         _nonObject -> throwM $ FieldNotResolvedException fieldName
 
 -- | Takes an argument name, validates that the argument exists, and optionally

src/Language/GraphQL/TH.hs

@@ -0,0 +1,49 @@
+{- 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/. -}
+
+module Language.GraphQL.TH
+    ( gql
+    ) where
+
+import Language.Haskell.TH
+    ( Exp(..)
+    , Lit(..)
+    )
+import Language.Haskell.TH.Quote (QuasiQuoter(..))
+
+stripIndentation :: String -> String
+stripIndentation code = reverse
+    $ dropWhile isLineBreak
+    $ reverse
+    $ unlines
+    $ indent spaces <$> lines' withoutLeadingNewlines
+  where
+    indent 0 xs = xs
+    indent count (' ' : xs) = indent (count - 1) xs
+    indent _ xs = xs
+    withoutLeadingNewlines = dropWhile isLineBreak code
+    spaces = length $ takeWhile (== ' ') withoutLeadingNewlines
+    lines' "" = []
+    lines' string =
+        let (line, rest) = break isLineBreak string
+            reminder =
+                case rest of
+                    [] -> []
+                    '\r' : '\n' : strippedString -> lines' strippedString
+                    _ : strippedString -> lines' strippedString
+         in line : reminder
+    isLineBreak = flip any ['\n', '\r'] . (==)
+
+-- | Removes leading and trailing newlines. Indentation of the first line is
+-- removed from each line of the string.
+gql :: QuasiQuoter
+gql = QuasiQuoter
+    { quoteExp = pure . LitE . StringL . stripIndentation
+    , quotePat = const
+        $ fail "Illegal gql QuasiQuote (allowed as expression only, used as a pattern)"
+    , quoteType = const
+        $ fail "Illegal gql QuasiQuote (allowed as expression only, used as a type)"
+    , quoteDec = const
+        $ fail "Illegal gql QuasiQuote (allowed as expression only, used as a declaration)"
+    }

tests/Language/GraphQL/ClassSpec.hs

@@ -3,14 +3,52 @@
    obtain one at https://mozilla.org/MPL/2.0/. -}
 
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE TemplateHaskell #-}
+
 module Language.GraphQL.ClassSpec
     ( spec
     ) where
 
 import Data.Text (Text)
+import Data.Time (UTCTime(..))
+import Data.Time.Calendar.OrdinalDate (fromOrdinalDate)
 import qualified Language.GraphQL.Type as Type
-import Language.GraphQL.Class (FromGraphQL(..), ToGraphQL(..))
+import Language.GraphQL.Class
+    ( FromGraphQL(..)
+    , ToGraphQL(..)
+    , deriveFromGraphQL
+    , deriveToGraphQL
+    )
 import Test.Hspec (Spec, describe, it, shouldBe)
+import qualified Data.HashMap.Strict as HashMap
+
+data TwoFieldRecord = TwoFieldRecord
+    { x :: Int
+    , y :: Bool
+    } deriving (Eq, Show)
+
+$(deriveToGraphQL ''TwoFieldRecord)
+$(deriveFromGraphQL ''TwoFieldRecord)
+
+data TwoVariantUnion
+    = FirstVariantUnion TwoFieldRecord
+    | SecondVariantUnion TwoFieldRecord
+    deriving (Eq, Show)
+
+$(deriveToGraphQL ''TwoVariantUnion)
+
+newtype NewTypeRecord = NewTypeRecord { newTypeField :: Int }
+    deriving (Eq, Show)
+
+$(deriveToGraphQL ''NewTypeRecord)
+$(deriveFromGraphQL ''NewTypeRecord)
+
+data TwoFieldEnum = TWO_FIELD_ENUM_1 | TWO_FIELD_ENUM_2
+    deriving (Eq, Show)
+
+$(deriveToGraphQL ''TwoFieldEnum)
+$(deriveFromGraphQL ''TwoFieldEnum)
 
 spec :: Spec
 spec = do
@@ -30,6 +68,15 @@ spec = do
         it "converts singleton lists" $
             toGraphQL [True] `shouldBe` Type.List [Type.Boolean True]
 
+        it "converts UTCTime" $
+            let given = UTCTime
+                    { utctDay = fromOrdinalDate 2023 5
+                    , utctDayTime = 90
+                    }
+                actual = toGraphQL given
+                expected = Type.String "2023-01-05T00:01:30Z"
+             in actual `shouldBe` expected
+
     describe "FromGraphQL" $ do
         it "converts integers" $
             fromGraphQL (Type.Int 5) `shouldBe` Just (5 :: Int)
@@ -45,3 +92,72 @@ spec = do
 
         it "converts singleton lists" $
             fromGraphQL (Type.List [Type.Boolean True]) `shouldBe` Just [True]
+
+        it "converts UTCTime" $
+            let given = Type.String "2023-01-05T00:01:30Z"
+                expected = Just $ UTCTime
+                    { utctDay = fromOrdinalDate 2023 5
+                    , utctDayTime = 90
+                    }
+                actual = fromGraphQL given
+             in actual `shouldBe` expected
+
+    describe "deriveToGraphQL" $ do
+        it "derives ToGraphQL for a record with multiple fields" $
+            let expected = Type.Object $ HashMap.fromList
+                    [ ("x", Type.Int 1)
+                    , ("y", Type.Boolean True)
+                    , ("__typename", Type.String "TwoFieldRecord")
+                    ]
+                given = TwoFieldRecord
+                    { x = 1
+                    , y = True
+                    }
+             in toGraphQL given `shouldBe` expected
+
+        it "derives ToGraphQL for a union" $
+            let expected = Type.Object $ HashMap.fromList
+                    [ ("x", Type.Int 2)
+                    , ("y", Type.Boolean False)
+                    , ("__typename", Type.String "TwoFieldRecord")
+                    ]
+                given = SecondVariantUnion $ TwoFieldRecord
+                    { x = 2
+                    , y = False
+                    }
+             in toGraphQL given `shouldBe` expected
+
+        it "derives ToGraphQL for a newtype record" $
+            let expected = Type.Object $ HashMap.fromList
+                    [ ("newTypeField", Type.Int 3)
+                    , ("__typename", Type.String "NewTypeRecord")
+                    ]
+                given = NewTypeRecord 3
+             in toGraphQL given `shouldBe` expected
+
+        it "derives ToGraphQL for an enumeration" $
+            let expected = Type.Enum "TWO_FIELD_ENUM_2"
+                given = TWO_FIELD_ENUM_2
+             in toGraphQL given `shouldBe` expected
+
+    describe "deriveFromGraphQL" $ do
+        it "derives FromGraphQL for a record with multiple fields" $
+            let given = Type.Object $ HashMap.fromList
+                    [ ("x", Type.Int 1)
+                    , ("y", Type.Boolean True)
+                    ]
+                expected = TwoFieldRecord
+                    { x = 1
+                    , y = True
+                    }
+             in fromGraphQL given `shouldBe` Just expected
+
+        it "derives FromGraphQL for a newtype record" $
+            let given = Type.Object $ HashMap.singleton "newTypeField" (Type.Int 3)
+                expected = NewTypeRecord 3
+             in fromGraphQL given `shouldBe` Just expected
+
+        it "derives FromGraphQL for an enumeration" $
+            let given = Type.Enum "TWO_FIELD_ENUM_2"
+                expected = TWO_FIELD_ENUM_2
+             in fromGraphQL given `shouldBe` Just expected

tests/Language/GraphQL/CoerceSpec.hs

@@ -3,6 +3,7 @@
    obtain one at https://mozilla.org/MPL/2.0/. -}
 
 {-# LANGUAGE OverloadedStrings #-}
+
 module Language.GraphQL.CoerceSpec
     ( spec
     ) where

tests/Language/GraphQL/DirectiveSpec.hs

@@ -4,7 +4,6 @@
 
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE PackageImports #-}
 
 module Language.GraphQL.DirectiveSpec
     ( spec
@@ -18,7 +17,7 @@ import Language.GraphQL.TH
 import Language.GraphQL.Type
 import qualified Language.GraphQL.Type.Out as Out
 import Test.Hspec (Spec, describe, it)
-import "graphql-spice" Test.Hspec.GraphQL
+import Test.Hspec.GraphQL
 
 experimentalResolver :: Schema IO
 experimentalResolver = schema queryType Nothing Nothing mempty

tests/Language/GraphQL/FragmentSpec.hs

@@ -4,7 +4,6 @@
 
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE PackageImports #-}
 
 module Language.GraphQL.FragmentSpec
     ( spec
@@ -20,7 +19,7 @@ import qualified Language.GraphQL.Type.Out as Out
 import Language.GraphQL.TH
 import qualified Language.GraphQL as GraphQL
 import Test.Hspec (Spec, describe, it)
-import "graphql-spice" Test.Hspec.GraphQL
+import Test.Hspec.GraphQL
 
 size :: (Text, Value)
 size = ("size", String "L")

tests/Language/GraphQL/RootOperationSpec.hs

@@ -4,7 +4,6 @@
 
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE QuasiQuotes #-}
-{-# LANGUAGE PackageImports #-}
 
 module Language.GraphQL.RootOperationSpec
     ( spec
@@ -18,7 +17,7 @@ import Test.Hspec (Spec, describe, it)
 import Language.GraphQL.TH
 import Language.GraphQL.Type
 import qualified Language.GraphQL.Type.Out as Out
-import "graphql-spice" Test.Hspec.GraphQL
+import Test.Hspec.GraphQL
 
 hatType :: Out.ObjectType IO
 hatType = Out.ObjectType "Hat" Nothing []

tests/Language/GraphQL/THSpec.hs

@@ -0,0 +1,27 @@
+{- 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.THSpec
+    ( spec
+    ) where
+
+import Data.Text (Text)
+import Language.GraphQL.TH (gql)
+import Test.Hspec (Spec, describe, it, shouldBe)
+
+spec :: Spec
+spec = do
+    describe "gql" $
+        it "replaces CRNL with NL" $
+            let expected :: Text
+                expected = "line1\nline2\nline3"
+                actual = [gql|
+                  line1
+                  line2
+                  line3
+                |]
+             in actual `shouldBe` expected