Add allow wrapping the return result in Identity.

Why:

Often two very similar types exist in the application.
1) The type returned from the server.
2) The type used by a component.
Frequently enough the only difference between the two is that some fields are wrapped in a functor. So if we allow wrapping the results in Identity, we will be able to share the type definition. E.g.

type Data f = { id: ID, name: f String }

type Return = Data Identity
type State = Data (Either Union)

Thus Identity fulfills a similar role to ErrorBoundary, but is a newtype.

spago.dhall

@@ -29,6 +29,7 @@ You can edit this file as you like.
   , "halogen-subscriptions"
   , "heterogeneous"
   , "http-methods"
+  , "identity"
   , "integers"
   , "lists"
   , "maybe"

src/GraphQL/Client/QueryReturns.purs

@@ -8,6 +8,7 @@ module GraphQL.Client.QueryReturns
 
 import Prelude
 
+import Data.Identity (Identity(..))
 import Data.Maybe (Maybe)
 import Data.Newtype (class Newtype, unwrap)
 import Data.Symbol (class IsSymbol)
@@ -55,6 +56,8 @@ else instance queryReturnsGqlType :: QueryReturnsAt at a q t => QueryReturnsAt a
   queryReturnsAtImpl at _ q = queryReturnsAtImpl at (undefined :: a) q
 else instance queryReturnsApplyDirective :: QueryReturnsAt at a q t => QueryReturnsAt at a (ApplyDirective name args q) t where
   queryReturnsAtImpl at a _ = queryReturnsAtImpl at a (undefined :: q)
+else instance queryReturnsIdentity :: QueryReturnsAt at a q t => QueryReturnsAt at a (Identity q) (Identity t) where
+  queryReturnsAtImpl at a _ = Identity $ queryReturnsAtImpl at a (undefined :: q)  
 else instance queryReturnErrorBoundary :: QueryReturnsAt at a q t => QueryReturnsAt at a (ErrorBoundary q) (BoundaryResult Unit t) where
   queryReturnsAtImpl at a _ = ErrorBoundary.Result $ queryReturnsAtImpl at a (undefined :: q)
 else instance queryReturnsSpread ::
@@ -75,9 +78,9 @@ else instance queryReturnsArray :: QueryReturnsAt at a q t => QueryReturnsAt at
 else instance queryReturnsMaybe :: QueryReturnsAt at a q t => QueryReturnsAt at (Maybe a) q (Maybe t) where
   queryReturnsAtImpl at _ q = pure $ queryReturnsAtImpl at (undefined :: a) q
 else instance queryReturnsUnion ::
-  HMapWithIndex (PropToSchemaType schema) (Record query) (Record returns) =>
+  HMapWithIndex (PropToSchemaType schema) { | query} { | returns } =>
   QueryReturnsAt at (GqlUnion schema) (GqlUnion query) (UnionReturned returns) where
-  queryReturnsAtImpl at _ _ = undefined
+  queryReturnsAtImpl _ _ _ = undefined
 else instance queryReturnsParamsArgs ::
   ( QueryReturnsAt at t q result
   , HMapWithIndex (ArgPropToGql params) { | args } s

src/GraphQL/Client/ToGqlString.purs

@@ -41,6 +41,7 @@ import Data.DateTime as DT
 import Data.Enum (class BoundedEnum, fromEnum)
 import Data.FoldableWithIndex (foldlWithIndex)
 import Data.Function (on)
+import Data.Identity (Identity(..))
 import Data.List (List)
 import Data.List as List
 import Data.Map (Map)
@@ -108,6 +109,8 @@ else instance gqlQueryStringApplyDirective ::
       <> reflectSymbol (Proxy :: Proxy name)
       <> gqlArgStringRecordTopLevel args
       <> toGqlQueryStringImpl opts q
+else instance gqlQueryStringIdentity :: GqlQueryString a => GqlQueryString (Identity a) where
+  toGqlQueryStringImpl opts (Identity a) = toGqlQueryStringImpl opts a
 else instance gqlQueryStringErrorBoundary :: GqlQueryString a => GqlQueryString (ErrorBoundary a) where
   toGqlQueryStringImpl opts (ErrorBoundary a) = toGqlQueryStringImpl opts a
 else instance gqlQueryStringSymbol :: IsSymbol s => GqlQueryString (Proxy s) where
@@ -484,4 +487,3 @@ else instance isIgnoreArgOrArg :: (IsIgnoreArg l, IsIgnoreArg r) => IsIgnoreArg
     ArgR r -> isIgnoreArg r
 else instance isIgnoreArgOther :: IsIgnoreArg a where
   isIgnoreArg _ = false
-

test/GraphQL/Client/QueryReturns.Test.purs

@@ -2,6 +2,7 @@ module GraphQL.Client.QueryReturns.Test where
 
 import Prelude
 
+import Data.Identity (Identity(..))
 import Data.Maybe (Maybe(..))
 import Data.Newtype (class Newtype)
 import GraphQL.Client.Alias ((:))
@@ -328,6 +329,23 @@ testDirective =
               =>> { id }
         }
 
+testIdentity
+  :: Proxy
+       { users ::
+           Array
+             { id :: Identity Int
+             }
+       }
+testIdentity =
+  queryReturns testSchemaProxy
+    $ 
+        { users:
+            { is_in_rec:
+                [ { int: 0 } ] +++ ((ArgR [ ignoreOrStr true, ignoreOrStr false ]) :: OrArg IgnoreArg _)
+            }
+              =>> { id: Identity id }
+        }        
+
 ignoreOrStr
   :: Boolean
   -> OrArg IgnoreArg