Pass root field names together with resolvers
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@ -31,14 +31,16 @@ import Control.Monad.Trans.Class (lift)
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import Control.Monad.Trans.State ( get
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, put
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)
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import Data.Foldable (fold)
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import Data.Foldable ( find
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, fold
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)
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import Data.GraphQL.Error
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import Data.List.NonEmpty (NonEmpty)
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import Data.Maybe (fromMaybe)
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import Data.Monoid (Alt(..))
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import qualified Data.Aeson as Aeson
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import Data.HashMap.Strict (HashMap)
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import qualified Data.HashMap.Strict as HashMap
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import Data.Text (Text)
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import qualified Data.Text as T
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import Data.GraphQL.AST.Core
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@ -48,10 +50,10 @@ import Data.GraphQL.AST.Core
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type Schema m = NonEmpty (Resolver m)
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-- | Resolves a 'Field' into an @Aeson.@'Aeson.Object' with error information
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-- (or 'empty'). @f@ is usually expected to be an instance of 'Alternative'.
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type Resolver m = Field -> CollectErrsT m Aeson.Object
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type Resolvers m = [Resolver m]
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-- (or 'empty'). @m@ is usually expected to be an instance of 'MonadPlus'.
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data Resolver m = Resolver
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Text -- ^ Name
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(Field -> CollectErrsT m Aeson.Object) -- ^ Resolver
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type Fields = [Field]
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@ -61,7 +63,7 @@ type Arguments = [Argument]
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type Subs = Name -> Maybe Value
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-- | Create a new 'Resolver' with the given 'Name' from the given 'Resolver's.
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object :: MonadPlus m => Name -> Resolvers m -> Resolver m
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object :: MonadPlus m => Name -> [Resolver m] -> Resolver m
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object name resolvers = objectA name $ \case
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[] -> resolvers
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_ -> empty
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@ -69,12 +71,14 @@ object name resolvers = objectA name $ \case
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-- | Like 'object' but also taking 'Argument's.
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objectA
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:: MonadPlus m
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=> Name -> (Arguments -> Resolvers m) -> Resolver m
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objectA name f fld@(Field _ _ args flds) = withField name (resolve (f args) flds) fld
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=> Name -> (Arguments -> [Resolver m]) -> Resolver m
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objectA name f = Resolver name go
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where
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go fld@(Field _ _ args flds) = withField name (resolve (f args) flds) fld
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-- | Create a named 'Resolver' from a list of 'Resolver's.
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object' :: MonadPlus m => Name -> m (Resolvers m) -> Resolver m
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object' :: MonadPlus m => Name -> m [Resolver m] -> Resolver m
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object' name resolvs = objectA' name $ \case
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[] -> resolvs
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_ -> empty
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@ -82,10 +86,12 @@ object' name resolvs = objectA' name $ \case
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-- | Like 'object'' but also taking 'Argument's.
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objectA'
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:: MonadPlus m
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=> Name -> (Arguments -> m (Resolvers m)) -> Resolver m
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objectA' name f fld@(Field _ _ args flds) = do
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resolvs <- lift $ f args
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withField name (resolve resolvs flds) fld
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=> Name -> (Arguments -> m [Resolver m]) -> Resolver m
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objectA' name f = Resolver name go
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where
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go fld@(Field _ _ args flds) = do
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resolvs <- lift $ f args
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withField name (resolve resolvs flds) fld
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-- | A scalar represents a primitive value, like a string or an integer.
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scalar :: (MonadPlus m, Aeson.ToJSON a) => Name -> a -> Resolver m
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@ -97,10 +103,12 @@ scalar name s = scalarA name $ \case
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scalarA
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:: (MonadPlus m, Aeson.ToJSON a)
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=> Name -> (Arguments -> m a) -> Resolver m
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scalarA name f fld@(Field _ _ args []) = withField name (lift $ f args) fld
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scalarA _ _ _ = empty
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scalarA name f = Resolver name go
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where
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go fld@(Field _ _ args []) = withField name (lift $ f args) fld
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go _ = empty
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array :: MonadPlus m => Name -> [Resolvers m] -> Resolver m
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array :: MonadPlus m => Name -> [[Resolver m]] -> Resolver m
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array name resolvers = arrayA name $ \case
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[] -> resolvers
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_ -> empty
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@ -108,12 +116,13 @@ array name resolvers = arrayA name $ \case
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-- | Like 'array' but also taking 'Argument's.
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arrayA
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:: MonadPlus m
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=> Name -> (Arguments -> [Resolvers m]) -> Resolver m
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arrayA name f fld@(Field _ _ args sels) =
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withField name (traverse (`resolve` sels) $ f args) fld
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=> Name -> (Arguments -> [[Resolver m]]) -> Resolver m
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arrayA name f = Resolver name go
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where
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go fld@(Field _ _ args sels) = withField name (traverse (`resolve` sels) $ f args) fld
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-- | Like 'object'' but taking lists of 'Resolver's instead of a single list.
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array' :: MonadPlus m => Name -> m [Resolvers m] -> Resolver m
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array' :: MonadPlus m => Name -> m [[Resolver m]] -> Resolver m
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array' name resolvs = arrayA' name $ \case
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[] -> resolvs
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_ -> empty
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@ -121,46 +130,50 @@ array' name resolvs = arrayA' name $ \case
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-- | Like 'array'' but also taking 'Argument's.
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arrayA'
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:: MonadPlus m
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=> Name -> (Arguments -> m [Resolvers m]) -> Resolver m
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arrayA' name f fld@(Field _ _ args sels) = do
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resolvs <- lift $ f args
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withField name (traverse (`resolve` sels) resolvs) fld
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=> Name -> (Arguments -> m [[Resolver m]]) -> Resolver m
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arrayA' name f = Resolver name go
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where
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go fld@(Field _ _ args sels) = do
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resolvs <- lift $ f args
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withField name (traverse (`resolve` sels) resolvs) fld
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-- | Represents one of a finite set of possible values.
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-- Used in place of a 'scalar' when the possible responses are easily enumerable.
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enum :: MonadPlus m => Name -> m [T.Text] -> Resolver m
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enum :: MonadPlus m => Name -> m [Text] -> Resolver m
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enum name enums = enumA name $ \case
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[] -> enums
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_ -> empty
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-- | Like 'enum' but also taking 'Argument's.
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enumA :: MonadPlus m => Name -> (Arguments -> m [T.Text]) -> Resolver m
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enumA name f fld@(Field _ _ args []) = withField name (lift $ f args) fld
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enumA _ _ _ = empty
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enumA :: MonadPlus m => Name -> (Arguments -> m [Text]) -> Resolver m
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enumA name f = Resolver name go
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where
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go fld@(Field _ _ args []) = withField name (lift $ f args) fld
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go _ = empty
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-- | Helper function to facilitate 'Argument' handling.
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withField :: (MonadPlus m, Aeson.ToJSON a)
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=> Name -> CollectErrsT m a -> Field -> CollectErrsT m (HashMap T.Text Aeson.Value)
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withField name v (Field alias name' _ _)
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| name == name' = do
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collection <- HashMap.singleton aliasOrName . Aeson.toJSON <$> runAppendErrs v
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errors <- get
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if null errors
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then return collection
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-- TODO: Report error when Non-Nullable type for field argument.
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else put [] >> return (HashMap.singleton aliasOrName Aeson.Null)
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| otherwise = empty
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=> Name -> CollectErrsT m a -> Field -> CollectErrsT m (HashMap Text Aeson.Value)
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withField name v (Field alias _ _ _) = do
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collection <- HashMap.singleton aliasOrName . Aeson.toJSON <$> runAppendErrs v
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errors <- get
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if null errors
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then return collection
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-- TODO: Report error when Non-Nullable type for field argument.
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else put [] >> return (HashMap.singleton aliasOrName Aeson.Null)
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where
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aliasOrName = fromMaybe name alias
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-- | Takes a list of 'Resolver's and a list of 'Field's and applies each
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-- 'Resolver' to each 'Field'. Resolves into a value containing the
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-- resolved 'Field', or a null value and error information.
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resolve :: MonadPlus m => Resolvers m -> Fields -> CollectErrsT m Aeson.Value
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resolve resolvers =
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fmap (Aeson.toJSON . fold)
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. traverse (\fld -> getAlt (foldMap (Alt . ($ fld)) resolvers) <|> errmsg fld)
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resolve :: MonadPlus m
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=> [Resolver m] -> Fields -> CollectErrsT m Aeson.Value
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resolve resolvers = fmap (Aeson.toJSON . fold) . traverse tryResolvers
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where
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tryResolvers fld = maybe empty (tryResolver fld) (find (compareResolvers fld) resolvers) <|> errmsg fld
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compareResolvers (Field _ name _ _) (Resolver name' _) = name == name'
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tryResolver fld (Resolver _ resolver) = resolver fld
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errmsg (Field alias name _ _) = do
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addErrMsg $ T.unwords ["field", name, "not resolved."]
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return $ HashMap.singleton aliasOrName Aeson.Null
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