proper nil support for lists

example/starwars/starwars.go

@@ -279,11 +279,11 @@ func (r *Resolver) Hero(args struct{ Episode string }) characterResolver {
 	return &droidResolver{droidData["2001"]}
 }
 
-func (r *Resolver) Reviews(args struct{ Episode string }) []*reviewResolver {
+func (r *Resolver) Reviews(args struct{ Episode string }) *[]*reviewResolver {
 	panic("TODO")
 }
 
-func (r *Resolver) Search(args struct{ Text string }) []searchResultResolver {
+func (r *Resolver) Search(args struct{ Text string }) *[]searchResultResolver {
 	var l []searchResultResolver
 	for _, h := range humans {
 		if strings.Contains(h.Name, args.Text) {
@@ -300,7 +300,7 @@ func (r *Resolver) Search(args struct{ Text string }) []searchResultResolver {
 			l = append(l, &starshipResolver{s})
 		}
 	}
-	return l
+	return &l
 }
 
 func (r *Resolver) Character(args struct{ ID string }) characterResolver {
@@ -342,7 +342,7 @@ type friendsConenctionArgs struct {
 type characterResolver interface {
 	ID() string
 	Name() string
-	Friends() []characterResolver
+	Friends() *[]characterResolver
 	FriendsConnection(friendsConenctionArgs) *friendsConnectionResolver
 	AppearsIn() []string
 	ToHuman() (*humanResolver, bool)
@@ -369,7 +369,7 @@ func (r *humanResolver) Mass() float64 {
 	return float64(r.h.Mass)
 }
 
-func (r *humanResolver) Friends() []characterResolver {
+func (r *humanResolver) Friends() *[]characterResolver {
 	return resolveCharacters(r.h.Friends)
 }
 
@@ -381,12 +381,12 @@ func (r *humanResolver) AppearsIn() []string {
 	return r.h.AppearsIn
 }
 
-func (r *humanResolver) Starships() []*starshipResolver {
+func (r *humanResolver) Starships() *[]*starshipResolver {
 	l := make([]*starshipResolver, len(r.h.Starships))
 	for i, id := range r.h.Starships {
 		l[i] = &starshipResolver{starshipData[id]}
 	}
-	return l
+	return &l
 }
 
 func (r *humanResolver) ToHuman() (*humanResolver, bool) {
@@ -413,7 +413,7 @@ func (r *droidResolver) Name() string {
 	return r.d.Name
 }
 
-func (r *droidResolver) Friends() []characterResolver {
+func (r *droidResolver) Friends() *[]characterResolver {
 	return resolveCharacters(r.d.Friends)
 }
 
@@ -486,7 +486,7 @@ func convertLength(meters float64, unit string) float64 {
 	}
 }
 
-func resolveCharacters(ids []string) []characterResolver {
+func resolveCharacters(ids []string) *[]characterResolver {
 	var characters []characterResolver
 	for _, id := range ids {
 		if h, ok := humanData[id]; ok {
@@ -496,7 +496,7 @@ func resolveCharacters(ids []string) []characterResolver {
 			characters = append(characters, &droidResolver{d})
 		}
 	}
-	return characters
+	return &characters
 }
 
 type reviewResolver struct {
@@ -517,11 +517,11 @@ func (r *friendsConnectionResolver) TotalCount() int {
 	panic("TODO")
 }
 
-func (r *friendsConnectionResolver) Edges() []*friendsEdgeResolver {
+func (r *friendsConnectionResolver) Edges() *[]*friendsEdgeResolver {
 	panic("TODO")
 }
 
-func (r *friendsConnectionResolver) Friends() []characterResolver {
+func (r *friendsConnectionResolver) Friends() *[]characterResolver {
 	panic("TODO")
 }
 

internal/exec/exec.go

@@ -66,7 +66,7 @@ func makeExec(target *iExec, s *schema.Schema, t schema.Type, resolverType refle
 		ref = &typeRef{}
 		typeRefMap[k] = ref
 		var err error
-		ref.exec, err = makeExec2(s, t, resolverType, typeRefMap)
+		ref.exec, err = makeExec2(s, t, false, resolverType, typeRefMap)
 		if err != nil {
 			return err
 		}
@@ -75,7 +75,7 @@ func makeExec(target *iExec, s *schema.Schema, t schema.Type, resolverType refle
 	return nil
 }
 
-func makeExec2(s *schema.Schema, t schema.Type, resolverType reflect.Type, typeRefMap map[typeRefMapKey]*typeRef) (iExec, error) {
+func makeExec2(s *schema.Schema, t schema.Type, nonNull bool, resolverType reflect.Type, typeRefMap map[typeRefMapKey]*typeRef) (iExec, error) {
 	switch t := t.(type) {
 	case *schema.Scalar:
 		return &scalarExec{}, nil
@@ -122,21 +122,23 @@ func makeExec2(s *schema.Schema, t schema.Type, resolverType reflect.Type, typeR
 		return &scalarExec{}, nil
 
 	case *schema.List:
+		if !nonNull {
+			if resolverType.Kind() != reflect.Ptr {
+				return nil, fmt.Errorf("%s is not a pointer", resolverType)
+			}
+			resolverType = resolverType.Elem()
+		}
 		if resolverType.Kind() != reflect.Slice {
 			return nil, fmt.Errorf("%s is not a slice", resolverType)
 		}
-		e := &listExec{}
+		e := &listExec{nonNull: nonNull}
 		if err := makeExec(&e.elem, s, t.Elem, resolverType.Elem(), typeRefMap); err != nil {
 			return nil, err
 		}
 		return e, nil
 
 	case *schema.NonNull:
-		e := &nonNilExec{}
-		if err := makeExec(&e.elem, s, t.Elem, resolverType, typeRefMap); err != nil {
-			return nil, err
-		}
-		return e, nil
+		return makeExec2(s, t.Elem, true, resolverType, typeRefMap)
 
 	default:
 		panic("invalid type")
@@ -291,10 +293,17 @@ func (e *scalarExec) exec(r *request, selSet *query.SelectionSet, resolver refle
 }
 
 type listExec struct {
-	elem iExec
+	elem    iExec
+	nonNull bool
 }
 
 func (e *listExec) exec(r *request, selSet *query.SelectionSet, resolver reflect.Value) interface{} {
+	if !e.nonNull {
+		if resolver.IsNil() {
+			return nil
+		}
+		resolver = resolver.Elem()
+	}
 	l := make([]interface{}, resolver.Len())
 	var wg sync.WaitGroup
 	for i := range l {
@@ -460,15 +469,6 @@ type typeAssertExec struct {
 	typeExec    iExec
 }
 
-type nonNilExec struct {
-	elem iExec
-}
-
-func (e *nonNilExec) exec(r *request, selSet *query.SelectionSet, resolver reflect.Value) interface{} {
-	// TODO ensure non-nil result
-	return e.elem.exec(r, selSet, resolver)
-}
-
 func skipByDirective(r *request, d map[string]*query.Directive) bool {
 	if skip, ok := d["skip"]; ok {
 		if execValue(r, skip.Arguments["if"]).(bool) {

internal/exec/introspection.go

@@ -221,7 +221,7 @@ func (r *typeResolver) Description() string {
 	return ""
 }
 
-func (r *typeResolver) Fields(args struct{ IncludeDeprecated bool }) []*fieldResolver {
+func (r *typeResolver) Fields(args struct{ IncludeDeprecated bool }) *[]*fieldResolver {
 	var fields map[string]*schema.Field
 	var fieldOrder []string
 	switch t := r.typ.(type) {
@@ -239,18 +239,18 @@ func (r *typeResolver) Fields(args struct{ IncludeDeprecated bool }) []*fieldRes
 	for i, name := range fieldOrder {
 		l[i] = &fieldResolver{fields[name]}
 	}
-	return l
+	return &l
 }
 
-func (r *typeResolver) Interfaces() []*typeResolver {
+func (r *typeResolver) Interfaces() *[]*typeResolver {
 	panic("TODO")
 }
 
-func (r *typeResolver) PossibleTypes() []*typeResolver {
+func (r *typeResolver) PossibleTypes() *[]*typeResolver {
 	panic("TODO")
 }
 
-func (r *typeResolver) EnumValues(args struct{ IncludeDeprecated bool }) []*enumValueResolver {
+func (r *typeResolver) EnumValues(args struct{ IncludeDeprecated bool }) *[]*enumValueResolver {
 	t, ok := r.typ.(*schema.Enum)
 	if !ok {
 		return nil
@@ -260,10 +260,10 @@ func (r *typeResolver) EnumValues(args struct{ IncludeDeprecated bool }) []*enum
 	for i, v := range t.Values {
 		l[i] = &enumValueResolver{v}
 	}
-	return l
+	return &l
 }
 
-func (r *typeResolver) InputFields() []*inputValueResolver {
+func (r *typeResolver) InputFields() *[]*inputValueResolver {
 	panic("TODO")
 }