GraphQL.Resolver

Documentation

data ResolverError

Constructors

SchemaError NameError

There was a problem in the schema. Server-side problem.

FieldNotFoundError Name

Couldn't find the requested field in the object. A client-side problem.

ValueMissing Name

No value provided for name, and no default specified. Client-side problem.

InvalidValue Name Text

Could not translate value into Haskell. Probably a client-side problem.

ValidationError ValidationErrors

Found validation errors when we tried to merge fields.

SubSelectionOnLeaf (SelectionSetByType Value)

Tried to get subselection of leaf field.

MissingSelectionSet

Tried to treat an object as a leaf.

Instances

Eq ResolverError

Methods

(==) :: ResolverError -> ResolverError -> Bool

(/=) :: ResolverError -> ResolverError -> Bool

Show ResolverError

Methods

showsPrec :: Int -> ResolverError -> ShowS

show :: ResolverError -> String

showList :: [ResolverError] -> ShowS

GraphQLError ResolverError

Methods

formatError :: ResolverError -> Text

toError :: ResolverError -> Error

class HasResolver m a where

Minimal complete definition

resolve

Associated Types

type Handler m a

Methods

resolve :: Handler m a -> Maybe (SelectionSetByType Value) -> m (Result Value)

Instances

Applicative m => HasResolver * m Bool

Associated Types

type Handler m (Bool :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m Bool a -> Maybe (SelectionSetByType Value) -> Bool (Result Value)

Applicative m => HasResolver * m Text

Associated Types

type Handler m (Text :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m Text a -> Maybe (SelectionSetByType Value) -> Text (Result Value)

Applicative m => HasResolver * m Double

Associated Types

type Handler m (Double :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m Double a -> Maybe (SelectionSetByType Value) -> Double (Result Value)

Applicative m => HasResolver * m Int32

Associated Types

type Handler m (Int32 :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m Int32 a -> Maybe (SelectionSetByType Value) -> Int32 (Result Value)

(HasResolver * m hg, Functor m, ToValue (Maybe hg)) => HasResolver * m (Maybe hg)

Associated Types

type Handler m (Maybe hg :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m (Maybe hg) a -> Maybe (SelectionSetByType Value) -> Maybe hg (Result Value)

(Monad m, Applicative m, HasResolver Type m hg) => HasResolver * m (List hg)

Associated Types

type Handler m (List hg :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m (List hg) a -> Maybe (SelectionSetByType Value) -> List hg (Result Value)

(Monad m, KnownSymbol unionName, RunUnion [Type] m (Union unionName objects) objects) => HasResolver * m (Union unionName objects)

Associated Types

type Handler m (Union unionName objects :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m (Union unionName objects) a -> Maybe (SelectionSetByType Value) -> Union unionName objects (Result Value)

(Applicative m, GraphQLEnum enum) => HasResolver * m (Enum ksN enum)

Associated Types

type Handler m (Enum ksN enum :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m (Enum ksN enum) a -> Maybe (SelectionSetByType Value) -> Enum ksN enum (Result Value)

(RunFields m (RunFieldsType m fields), HasObjectDefinition * (Object typeName interfaces fields), Monad m) => HasResolver * m (Object typeName interfaces fields)

Associated Types

type Handler m (Object typeName interfaces fields :: * -> *) (a :: m) :: *

Methods

resolve :: Handler m (Object typeName interfaces fields) a -> Maybe (SelectionSetByType Value) -> Object typeName interfaces fields (Result Value)

data a :<> b infixr 8

Object field separation operator.

Use this to provide handlers for fields of an object.

Say you had the following GraphQL type with "foo" and "bar" fields, e.g.

  type MyObject {
    foo: Int!
    bar: String!
  }

You could provide handlers for it like this:

>>> :m +System.Environment
>>> let fooHandler = pure 42
>>> let barHandler = System.Environment.getProgName
>>> let myObjectHandler = pure $ fooHandler :<> barHandler :<> ()

Constructors

a :<> b infixr 8

class Defaultable a where

Specify a default value for a type in a GraphQL schema.

GraphQL schema can have default values in certain places. For example, arguments to fields can have default values. Because we cannot lift arbitrary values to the type level, we need some way of getting at those values. This typeclass provides the means.

To specify a default, implement this typeclass.

The default implementation is to say that there *is* no default for this type.

Methods

defaultFor :: Name -> Maybe a

defaultFor returns the value to be used when no value has been given.

Instances

Defaultable Bool

Methods

defaultFor :: Name -> Maybe Bool

Defaultable Double

Methods

defaultFor :: Name -> Maybe Double

Defaultable Int32

Methods

defaultFor :: Name -> Maybe Int32

Defaultable Text

Methods

defaultFor :: Name -> Maybe Text

Defaultable (Maybe a)

Methods

defaultFor :: Name -> Maybe (Maybe a)

data Result a

Constructors

Result [ResolverError] a

Instances

Functor Result

Methods

fmap :: (a -> b) -> Result a -> Result b

(<$) :: a -> Result b -> Result a

Applicative Result

Methods

pure :: a -> Result a

(<*>) :: Result (a -> b) -> Result a -> Result b

(*>) :: Result a -> Result b -> Result b

(<*) :: Result a -> Result b -> Result a

Eq a => Eq (Result a)

Methods

(==) :: Result a -> Result a -> Bool

(/=) :: Result a -> Result a -> Bool

Show a => Show (Result a)

Methods

showsPrec :: Int -> Result a -> ShowS

show :: Result a -> String

showList :: [Result a] -> ShowS

unionValue :: forall object union m name interfaces fields. (Monad m, Object name interfaces fields ~ object, KnownSymbol name) => TypeIndex m object union -> m (DynamicUnionValue union m)

Translate a Handler into a DynamicUnionValue type required by Union handlers. This is dynamic, but nevertheless type-safe because we can only tag with types that are part of the union.

Use e.g. like "unionValue @Cat" if you have an object like this:

>>> type Cat = API.Object "Cat" '[] '[API.Field "name" Text]

and then use `unionValue @Cat (pure (pure Felix))`. See `examples/UnionExample.hs` for more code.