Special handling for pointers to slices (#1363)

TESTING.md

@@ -5,7 +5,7 @@ Testing generated code is a little tricky, heres how its currently set up.
 
 ### Testing responses from a server
 
-There is a server in `codegen/testserver` that is generated as part 
+There is a server in `codegen/testserver` that is generated as part
 of `go generate ./...`, and tests written against it.
 
 There are also a bunch of tests in against the examples, feel free to take examples from there.
@@ -15,7 +15,7 @@ There are also a bunch of tests in against the examples, feel free to take examp
 
 These tests are **really** slow, because they need to run the whole codegen step. Use them very sparingly. If you can, find a way to unit test it instead.
 
-Take a look at `codegen/input_test.go` for an example.
+Take a look at `codegen/testserver/input_test.go` for an example.
 
 ### Testing introspection
 

codegen/config/binder.go

@@ -217,6 +217,14 @@ func (t *TypeReference) IsSlice() bool {
 	return t.GQL.Elem != nil && isSlice
 }
 
+func (t *TypeReference) IsPtrToSlice() bool {
+	if t.IsPtr() {
+		_, isPointerToSlice := t.GO.(*types.Pointer).Elem().(*types.Slice)
+		return isPointerToSlice
+	}
+	return false
+}
+
 func (t *TypeReference) IsNamed() bool {
 	_, isSlice := t.GO.(*types.Named)
 	return isSlice

codegen/testserver/ptr_to_slice.go

@@ -0,0 +1,5 @@
+package testserver
+
+type PtrToSliceContainer struct {
+	PtrToSlice *[]string
+}

codegen/testserver/ptr_to_slice.graphql

@@ -0,0 +1,7 @@
+type PtrToSliceContainer {
+    ptrToSlice: [String!]
+}
+
+extend type Query {
+    ptrToSliceContainer: PtrToSliceContainer!
+}

codegen/testserver/ptr_to_slice_test.go

@@ -0,0 +1,37 @@
+package testserver
+
+import (
+	"context"
+	"testing"
+
+	"github.com/99designs/gqlgen/client"
+	"github.com/99designs/gqlgen/graphql/handler"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPtrToSlice(t *testing.T) {
+	resolvers := &Stub{}
+
+	c := client.New(handler.NewDefaultServer(NewExecutableSchema(Config{Resolvers: resolvers})))
+
+	resolvers.QueryResolver.PtrToSliceContainer = func(ctx context.Context) (wrappedStruct *PtrToSliceContainer, e error) {
+		ptrToSliceContainer := PtrToSliceContainer{
+			PtrToSlice: &[]string{"hello"},
+		}
+		return &ptrToSliceContainer, nil
+	}
+
+	t.Run("pointer to slice", func(t *testing.T) {
+		var resp struct {
+			PtrToSliceContainer struct {
+				PtrToSlice []string
+			}
+		}
+
+		err := c.Post(`query { ptrToSliceContainer {  ptrToSlice }}`, &resp)
+		require.NoError(t, err)
+
+		require.Equal(t, []string{"hello"}, resp.PtrToSliceContainer.PtrToSlice)
+
+	})
+}

codegen/testserver/resolver.go

@@ -260,6 +260,10 @@ func (r *queryResolver) PrimitiveStringObject(ctx context.Context) ([]PrimitiveS
 	panic("not implemented")
 }
 
+func (r *queryResolver) PtrToSliceContainer(ctx context.Context) (*PtrToSliceContainer, error) {
+	panic("not implemented")
+}
+
 func (r *queryResolver) DefaultScalar(ctx context.Context, arg string) (string, error) {
 	panic("not implemented")
 }

codegen/type.go

@@ -26,7 +26,7 @@ func processType(ret map[string]*config.TypeReference, ref *config.TypeReference
 	}
 	ret[key] = ref
 
-	if ref.IsSlice() {
+	if ref.IsSlice() || ref.IsPtrToSlice() {
 		processType(ret, ref.Elem())
 	}
 }

codegen/type.gotpl

@@ -4,7 +4,10 @@
 			{{- if and $type.IsNilable (not $type.GQL.NonNull) }}
 				if v == nil { return nil, nil }
 			{{- end }}
-			{{- if $type.IsSlice }}
+			{{- if $type.IsPtrToSlice }}
+				res, err := ec.{{ $type.Elem.UnmarshalFunc }}(ctx, v)
+				return &res, graphql.ErrorOnPath(ctx, err)
+			{{- else if $type.IsSlice }}
 				var vSlice []interface{}
 				if v != nil {
 					if tmp1, ok := v.([]interface{}); ok {
@@ -66,7 +69,9 @@
 
 	{{ with $type.MarshalFunc }}
 		func (ec *executionContext) {{ . }}(ctx context.Context, sel ast.SelectionSet, v {{ $type.GO | ref }}) graphql.Marshaler {
-			{{- if $type.IsSlice }}
+			{{- if $type.IsPtrToSlice }}
+				return ec.{{ $type.Elem.MarshalFunc }}(ctx, sel, *v)
+			{{- else if $type.IsSlice }}
 				{{- if not $type.GQL.NonNull }}
 					if v == nil {
 						return graphql.Null