Pass root field names together with resolvers

This commit is contained in:
Eugen Wissner 2019-07-01 06:39:13 +02:00
parent f64e186c60
commit 1017b728d9

View File

@ -31,14 +31,16 @@ import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.State ( get
, put
)
import Data.Foldable (fold)
import Data.Foldable ( find
, fold
)
import Data.GraphQL.Error
import Data.List.NonEmpty (NonEmpty)
import Data.Maybe (fromMaybe)
import Data.Monoid (Alt(..))
import qualified Data.Aeson as Aeson
import Data.HashMap.Strict (HashMap)
import qualified Data.HashMap.Strict as HashMap
import Data.Text (Text)
import qualified Data.Text as T
import Data.GraphQL.AST.Core
@ -48,10 +50,10 @@ import Data.GraphQL.AST.Core
type Schema m = NonEmpty (Resolver m)
-- | Resolves a 'Field' into an @Aeson.@'Aeson.Object' with error information
-- (or 'empty'). @f@ is usually expected to be an instance of 'Alternative'.
type Resolver m = Field -> CollectErrsT m Aeson.Object
type Resolvers m = [Resolver m]
-- (or 'empty'). @m@ is usually expected to be an instance of 'MonadPlus'.
data Resolver m = Resolver
Text -- ^ Name
(Field -> CollectErrsT m Aeson.Object) -- ^ Resolver
type Fields = [Field]
@ -61,7 +63,7 @@ type Arguments = [Argument]
type Subs = Name -> Maybe Value
-- | Create a new 'Resolver' with the given 'Name' from the given 'Resolver's.
object :: MonadPlus m => Name -> Resolvers m -> Resolver m
object :: MonadPlus m => Name -> [Resolver m] -> Resolver m
object name resolvers = objectA name $ \case
[] -> resolvers
_ -> empty
@ -69,12 +71,14 @@ object name resolvers = objectA name $ \case
-- | Like 'object' but also taking 'Argument's.
objectA
:: MonadPlus m
=> Name -> (Arguments -> Resolvers m) -> Resolver m
objectA name f fld@(Field _ _ args flds) = withField name (resolve (f args) flds) fld
=> Name -> (Arguments -> [Resolver m]) -> Resolver m
objectA name f = Resolver name go
where
go fld@(Field _ _ args flds) = withField name (resolve (f args) flds) fld
-- | Create a named 'Resolver' from a list of 'Resolver's.
object' :: MonadPlus m => Name -> m (Resolvers m) -> Resolver m
object' :: MonadPlus m => Name -> m [Resolver m] -> Resolver m
object' name resolvs = objectA' name $ \case
[] -> resolvs
_ -> empty
@ -82,8 +86,10 @@ object' name resolvs = objectA' name $ \case
-- | Like 'object'' but also taking 'Argument's.
objectA'
:: MonadPlus m
=> Name -> (Arguments -> m (Resolvers m)) -> Resolver m
objectA' name f fld@(Field _ _ args flds) = do
=> Name -> (Arguments -> m [Resolver m]) -> Resolver m
objectA' name f = Resolver name go
where
go fld@(Field _ _ args flds) = do
resolvs <- lift $ f args
withField name (resolve resolvs flds) fld
@ -97,10 +103,12 @@ scalar name s = scalarA name $ \case
scalarA
:: (MonadPlus m, Aeson.ToJSON a)
=> Name -> (Arguments -> m a) -> Resolver m
scalarA name f fld@(Field _ _ args []) = withField name (lift $ f args) fld
scalarA _ _ _ = empty
scalarA name f = Resolver name go
where
go fld@(Field _ _ args []) = withField name (lift $ f args) fld
go _ = empty
array :: MonadPlus m => Name -> [Resolvers m] -> Resolver m
array :: MonadPlus m => Name -> [[Resolver m]] -> Resolver m
array name resolvers = arrayA name $ \case
[] -> resolvers
_ -> empty
@ -108,12 +116,13 @@ array name resolvers = arrayA name $ \case
-- | Like 'array' but also taking 'Argument's.
arrayA
:: MonadPlus m
=> Name -> (Arguments -> [Resolvers m]) -> Resolver m
arrayA name f fld@(Field _ _ args sels) =
withField name (traverse (`resolve` sels) $ f args) fld
=> Name -> (Arguments -> [[Resolver m]]) -> Resolver m
arrayA name f = Resolver name go
where
go fld@(Field _ _ args sels) = withField name (traverse (`resolve` sels) $ f args) fld
-- | Like 'object'' but taking lists of 'Resolver's instead of a single list.
array' :: MonadPlus m => Name -> m [Resolvers m] -> Resolver m
array' :: MonadPlus m => Name -> m [[Resolver m]] -> Resolver m
array' name resolvs = arrayA' name $ \case
[] -> resolvs
_ -> empty
@ -121,46 +130,50 @@ array' name resolvs = arrayA' name $ \case
-- | Like 'array'' but also taking 'Argument's.
arrayA'
:: MonadPlus m
=> Name -> (Arguments -> m [Resolvers m]) -> Resolver m
arrayA' name f fld@(Field _ _ args sels) = do
=> Name -> (Arguments -> m [[Resolver m]]) -> Resolver m
arrayA' name f = Resolver name go
where
go fld@(Field _ _ args sels) = do
resolvs <- lift $ f args
withField name (traverse (`resolve` sels) resolvs) fld
-- | Represents one of a finite set of possible values.
-- Used in place of a 'scalar' when the possible responses are easily enumerable.
enum :: MonadPlus m => Name -> m [T.Text] -> Resolver m
enum :: MonadPlus m => Name -> m [Text] -> Resolver m
enum name enums = enumA name $ \case
[] -> enums
_ -> empty
-- | Like 'enum' but also taking 'Argument's.
enumA :: MonadPlus m => Name -> (Arguments -> m [T.Text]) -> Resolver m
enumA name f fld@(Field _ _ args []) = withField name (lift $ f args) fld
enumA _ _ _ = empty
enumA :: MonadPlus m => Name -> (Arguments -> m [Text]) -> Resolver m
enumA name f = Resolver name go
where
go fld@(Field _ _ args []) = withField name (lift $ f args) fld
go _ = empty
-- | Helper function to facilitate 'Argument' handling.
withField :: (MonadPlus m, Aeson.ToJSON a)
=> Name -> CollectErrsT m a -> Field -> CollectErrsT m (HashMap T.Text Aeson.Value)
withField name v (Field alias name' _ _)
| name == name' = do
=> Name -> CollectErrsT m a -> Field -> CollectErrsT m (HashMap Text Aeson.Value)
withField name v (Field alias _ _ _) = do
collection <- HashMap.singleton aliasOrName . Aeson.toJSON <$> runAppendErrs v
errors <- get
if null errors
then return collection
-- TODO: Report error when Non-Nullable type for field argument.
else put [] >> return (HashMap.singleton aliasOrName Aeson.Null)
| otherwise = empty
where
aliasOrName = fromMaybe name alias
-- | Takes a list of 'Resolver's and a list of 'Field's and applies each
-- 'Resolver' to each 'Field'. Resolves into a value containing the
-- resolved 'Field', or a null value and error information.
resolve :: MonadPlus m => Resolvers m -> Fields -> CollectErrsT m Aeson.Value
resolve resolvers =
fmap (Aeson.toJSON . fold)
. traverse (\fld -> getAlt (foldMap (Alt . ($ fld)) resolvers) <|> errmsg fld)
resolve :: MonadPlus m
=> [Resolver m] -> Fields -> CollectErrsT m Aeson.Value
resolve resolvers = fmap (Aeson.toJSON . fold) . traverse tryResolvers
where
tryResolvers fld = maybe empty (tryResolver fld) (find (compareResolvers fld) resolvers) <|> errmsg fld
compareResolvers (Field _ name _ _) (Resolver name' _) = name == name'
tryResolver fld (Resolver _ resolver) = resolver fld
errmsg (Field alias name _ _) = do
addErrMsg $ T.unwords ["field", name, "not resolved."]
return $ HashMap.singleton aliasOrName Aeson.Null