Add a reader instance to the resolvers

The Reader contains a Name/Value hashmap, which will contain resolver
arguments.
This commit is contained in:
Eugen Wissner 2019-11-23 09:49:12 +01:00
parent 625d7100ca
commit 587aab005e
4 changed files with 35 additions and 8 deletions

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@ -14,6 +14,8 @@ All notable changes to this project will be documented in this file.
- `Language.GraphQL.AST.Transform` is isn't exposed publically anymore.
- `Language.GraphQL.Schema.resolve` accepts a selection `Seq` (`Data.Sequence`)
instead of a list. Selections are stored as sequences internally as well.
- Add a reader instance to the resolver's monad stack. The Reader contains
a Name/Value hashmap, which will contain resolver arguments.
### Added
- Nested fragment support.
@ -29,6 +31,19 @@ All notable changes to this project will be documented in this file.
- `Language.GraphQL.AST.Parser.type_`: Try type parsers in a variable
definition in a different order to avoid using `but`.
### Removed
- `Language.GraphQL.AST.Arguments`. Use `[Language.GraphQL.AST.Argument]`
instead.
- `Language.GraphQL.AST.Directives`. Use `[Language.GraphQL.AST.Directives]`
instead.
- `Language.GraphQL.AST.VariableDefinitions`. Use
`[Language.GraphQL.AST.VariableDefinition]` instead.
- `Language.GraphQL.AST.FragmentName`. Use `Language.GraphQL.AST.Name` instead.
- `Language.GraphQL.Execute.Schema` - It was a resolver list, not a schema.
- `Language.GraphQL.Schema`: `enum`, `enumA`, `wrappedEnum` and `wrappedEnumA`.
Use `scalar`, `scalarA`, `wrappedScalar` and `wrappedScalarA` instead.
## [0.5.1.0] - 2019-10-22
### Deprecated
- `Language.GraphQL.AST.Arguments`. Use `[Language.GraphQL.AST.Argument]`

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@ -23,10 +23,10 @@ import Data.Text.Lazy.Builder.Int (decimal)
import Data.Text.Lazy.Builder.RealFloat (realFloat)
import qualified Language.GraphQL.AST as Full
-- | Instructs the encoder whether a GraphQL should be minified or pretty
-- printed.
-- | Instructs the encoder whether the GraphQL document should be minified or
-- pretty printed.
--
-- Use 'pretty' and 'minified' to construct the formatter.
-- Use 'pretty' or 'minified' to construct the formatter.
data Formatter
= Minified
| Pretty Word

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@ -23,6 +23,7 @@ module Language.GraphQL.Schema
import Control.Monad.IO.Class (MonadIO(..))
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.Except (runExceptT)
import Control.Monad.Trans.Reader (runReaderT)
import Data.Foldable (find, fold)
import Data.Maybe (fromMaybe)
import qualified Data.Aeson as Aeson
@ -102,9 +103,10 @@ resolveFieldValue :: MonadIO m
-> Field
-> CollectErrsT m (HashMap Text Aeson.Value)
resolveFieldValue f resolveRight fld@(Field _ _ args _) = do
result <- lift $ runExceptT . runActionT $ f args
result <- lift $ reader . runExceptT . runActionT $ f args
either resolveLeft (resolveRight fld) result
where
reader = flip runReaderT $ Context mempty
resolveLeft err = do
_ <- addErrMsg err
return $ HashMap.singleton (aliasOrName fld) Aeson.Null

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@ -1,6 +1,7 @@
-- | Monad transformer stack used by the @GraphQL@ resolvers.
module Language.GraphQL.Trans
( ActionT(..)
, Context(Context)
) where
import Control.Applicative (Alternative(..))
@ -8,10 +9,19 @@ import Control.Monad (MonadPlus(..))
import Control.Monad.IO.Class (MonadIO(..))
import Control.Monad.Trans.Class (MonadTrans(..))
import Control.Monad.Trans.Except (ExceptT)
import Control.Monad.Trans.Reader (ReaderT)
import Data.HashMap.Strict (HashMap)
import Data.Text (Text)
import Language.GraphQL.AST.Core (Name, Value)
-- | Monad transformer stack used by the resolvers to provide error handling.
newtype ActionT m a = ActionT { runActionT :: ExceptT Text m a }
-- | Resolution context holds resolver arguments.
newtype Context = Context (HashMap Name Value)
-- | Monad transformer stack used by the resolvers to provide error handling
-- and resolution context (resolver arguments).
newtype ActionT m a = ActionT
{ runActionT :: ExceptT Text (ReaderT Context m) a
}
instance Functor m => Functor (ActionT m) where
fmap f = ActionT . fmap f . runActionT
@ -25,7 +35,7 @@ instance Monad m => Monad (ActionT m) where
(ActionT action) >>= f = ActionT $ action >>= runActionT . f
instance MonadTrans ActionT where
lift = ActionT . lift
lift = ActionT . lift . lift
instance MonadIO m => MonadIO (ActionT m) where
liftIO = lift . liftIO