Propagate Maybe in the transform tree
Since the transform tree can already find some errors, it may fail here and there. Almost all functions return a Maybe to signalize an error. Will be replaced with an Either of course.
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@ -1,5 +1,3 @@
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{-# LANGUAGE OverloadedStrings #-}
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-- | After the document is parsed, before getting executed the AST is
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-- transformed into a similar, simpler AST. This module is responsible for
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-- this transformation.
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@ -12,26 +10,24 @@ import Data.HashMap.Strict (HashMap)
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import qualified Data.HashMap.Strict as HashMap
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import Data.List.NonEmpty (NonEmpty)
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import qualified Data.List.NonEmpty as NonEmpty
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import Data.Maybe (fromMaybe)
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import qualified Language.GraphQL.AST as Full
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import qualified Language.GraphQL.AST.Core as Core
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import qualified Language.GraphQL.Schema as Schema
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-- | Associates a fragment name with a list of 'Core.Field's.
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type Fragments = HashMap Core.Name [Core.Field]
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type Fragments = HashMap Core.Name (NonEmpty Core.Field)
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-- | Rewrites the original syntax tree into an intermediate representation used
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-- for query execution.
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document :: Schema.Subs -> Full.Document -> Maybe Core.Document
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document subs doc = operations subs fragments operations'
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document subs doc =
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case fragments of
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Just fragments' -> operations subs fragments' operations'
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Nothing -> Nothing
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where
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(fragments, operations') = foldr (defrag subs) mempty
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(fragments, operations') = foldr (defrag subs) (Just HashMap.empty, [])
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$ NonEmpty.toList doc
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extractFragment :: Fragments -> Core.Name -> [Core.Selection]
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extractFragment fragments name = Core.SelectionField
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<$> fromMaybe mempty (HashMap.lookup name fragments)
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-- * Operation
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-- TODO: Replace Maybe by MonadThrow CustomError
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@ -53,27 +49,27 @@ operation subs fragments (Full.OperationSelectionSet sels) =
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operation subs fragments $ Full.OperationDefinition Full.Query mempty mempty mempty sels
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-- TODO: Validate Variable definitions with substituter
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operation subs fragments (Full.OperationDefinition Full.Query name _vars _dirs sels) =
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pure $ Core.Query name $ appendSelection subs fragments sels
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Core.Query name <$> appendSelection subs fragments sels
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operation subs fragments (Full.OperationDefinition Full.Mutation name _vars _dirs sels) =
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pure $ Core.Mutation name $ appendSelection subs fragments sels
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Core.Mutation name <$> appendSelection subs fragments sels
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selection ::
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Schema.Subs ->
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Fragments ->
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Full.Selection ->
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Either [Core.Selection] Core.Selection
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Maybe (Either (NonEmpty Core.Selection) Core.Selection)
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selection subs fragments (Full.SelectionField fld)
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= Right $ Core.SelectionField $ field subs fragments fld
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= Right . Core.SelectionField <$> field subs fragments fld
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selection _ fragments (Full.SelectionFragmentSpread (Full.FragmentSpread name _))
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= Left $ extractFragment fragments name
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= Left . fmap Core.SelectionField <$> HashMap.lookup name fragments
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selection subs fragments (Full.SelectionInlineFragment fragment)
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| (Full.InlineFragment (Just typeCondition) _ selectionSet) <- fragment
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= Right
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$ Core.SelectionFragment
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$ Core.Fragment typeCondition
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$ appendSelection subs fragments selectionSet
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. Core.SelectionFragment
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. Core.Fragment typeCondition
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<$> appendSelection subs fragments selectionSet
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| (Full.InlineFragment Nothing _ selectionSet) <- fragment
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= Left $ NonEmpty.toList $ appendSelection subs fragments selectionSet
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= Left <$> appendSelection subs fragments selectionSet
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-- * Fragment replacement
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@ -81,35 +77,37 @@ selection subs fragments (Full.SelectionInlineFragment fragment)
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defrag ::
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Schema.Subs ->
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Full.Definition ->
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(Fragments, [Full.OperationDefinition]) ->
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(Fragments, [Full.OperationDefinition])
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(Maybe Fragments, [Full.OperationDefinition]) ->
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(Maybe Fragments, [Full.OperationDefinition])
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defrag _ (Full.DefinitionOperation op) (fragments, operations') =
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(fragments, op : operations')
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defrag subs (Full.DefinitionFragment fragDef) (fragments, operations') =
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defrag subs (Full.DefinitionFragment fragDef) (Just fragments, operations') =
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(fragmentDefinition subs fragments fragDef, operations')
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defrag _ _ (Nothing, operations') =
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(Nothing, operations')
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fragmentDefinition ::
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Schema.Subs ->
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Fragments ->
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Full.FragmentDefinition ->
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Fragments
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fragmentDefinition subs fragments (Full.FragmentDefinition name _tc _dirs sels) =
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HashMap.insert name (extractField <$> emitValue) fragments
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Maybe Fragments
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fragmentDefinition subs fragments (Full.FragmentDefinition name _tc _dirs sels) = do
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emitted <- emitValue
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newValue <- traverse extractField emitted
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Just $ HashMap.insert name newValue fragments
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where
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emitValue :: Maybe (NonEmpty Core.Selection)
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emitValue = do
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selections <- NonEmpty.toList $ selection subs mempty <$> sels
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either id pure selections
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extractField (Core.SelectionField field') = field'
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extractField _ = error "Fragments within fragments are not supported yet"
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selections <- traverse (selection subs fragments) sels
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pure $ selections >>= either id pure
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extractField :: Core.Selection -> Maybe Core.Field
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extractField (Core.SelectionField field') = Just field'
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extractField _ = Nothing -- Fragments within fragments are not supported yet
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field :: Schema.Subs -> Fragments -> Full.Field -> Core.Field
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field :: Schema.Subs -> Fragments -> Full.Field -> Maybe Core.Field
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field subs fragments (Full.Field a n args _dirs sels) =
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Core.Field a n (fold $ argument subs `traverse` args) (foldr go mempty sels)
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where
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go :: Full.Selection -> [Core.Selection] -> [Core.Selection]
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go (Full.SelectionFragmentSpread (Full.FragmentSpread name _dirs)) =
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(extractFragment fragments name <>)
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go sel = (either id pure (selection subs fragments sel) <>)
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Core.Field a n (fold $ argument subs `traverse` args)
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<$> appendSelectionOpt subs fragments sels
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argument :: Schema.Subs -> Full.Argument -> Maybe Core.Argument
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argument subs (Full.Argument n v) = Core.Argument n <$> value subs v
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@ -130,10 +128,25 @@ value subs (Full.ValueObject o) =
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objectField :: Schema.Subs -> Full.ObjectField -> Maybe Core.ObjectField
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objectField subs (Full.ObjectField n v) = Core.ObjectField n <$> value subs v
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appendSelectionOpt ::
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Traversable t =>
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Schema.Subs ->
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Fragments ->
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t Full.Selection ->
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Maybe [Core.Selection]
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appendSelectionOpt subs fragments = foldr go (Just [])
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where
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go :: Full.Selection -> Maybe [Core.Selection] -> Maybe [Core.Selection]
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go _ Nothing = Nothing
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go sel (Just acc) = append acc <$> selection subs fragments sel
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append acc (Left list) = NonEmpty.toList list <> acc
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append acc (Right one) = one : acc
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appendSelection ::
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Schema.Subs ->
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Fragments ->
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NonEmpty Full.Selection ->
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NonEmpty Core.Selection
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appendSelection subs fragments = NonEmpty.fromList
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. foldr (either (++) (:) . selection subs fragments) []
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Maybe (NonEmpty Core.Selection)
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appendSelection subs fragments fullSelection = do
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coreSelection <-appendSelectionOpt subs fragments fullSelection
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NonEmpty.nonEmpty coreSelection
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