Merge pull request #148 from jainpiyush19/possibletypes_fix

Fix possible types not being returned for interface introspection

execution.go

@@ -396,14 +396,14 @@ func resolveType(ctx context.Context, schema *ast.Schema, typ *ast.Type, selecti
 			}
 			result[f.Alias] = interfaces
 		case "possibleTypes":
-			if len(namedType.Types) > 0 {
+			if namedType.Kind != ast.Interface && namedType.Kind != ast.Union {
+				result[f.Alias] = nil
+			} else {
 				types := []map[string]interface{}{}
-				for _, t := range namedType.Types {
-					types = append(types, resolveType(ctx, schema, &ast.Type{NamedType: t}, f.SelectionSet))
+				for _, t := range schema.PossibleTypes[namedType.Name] {
+					types = append(types, resolveType(ctx, schema, &ast.Type{NamedType: t.Name}, f.SelectionSet))
 				}
 				result[f.Alias] = types
-			} else {
-				result[f.Alias] = nil
 			}
 		case "enumValues":
 			includeDeprecated := false
@@ -425,13 +425,17 @@ func resolveType(ctx context.Context, schema *ast.Schema, typ *ast.Type, selecti
 			}
 			result[f.Alias] = enums
 		case "inputFields":
-			inputFields := []map[string]interface{}{}
-			for _, fi := range namedType.Fields {
-				// call resolveField instead of resolveInputValue because it has
-				// the right type and is a superset of it
-				inputFields = append(inputFields, resolveField(ctx, schema, fi, f.SelectionSet))
+			if namedType.Kind == ast.InputObject {
+				inputFields := []map[string]interface{}{}
+				for _, fi := range namedType.Fields {
+					// call resolveField instead of resolveInputValue because it has
+					// the right type and is a superset of it
+					inputFields = append(inputFields, resolveField(ctx, schema, fi, f.SelectionSet))
+				}
+				result[f.Alias] = inputFields
+			} else {
+				result[f.Alias] = nil
 			}
-			result[f.Alias] = inputFields
 		default:
 			result[f.Alias] = nil
 		}

execution_test.go

@@ -347,6 +347,31 @@ func TestIntrospectionQuery(t *testing.T) {
 		`, string(resp.Data))
 	})
 
+	t.Run("interface", func(t *testing.T) {
+		query := gqlparser.MustLoadQuery(es.MergedSchema, `
+		{
+			__type(name: "Person") {
+				possibleTypes {
+					name
+				}
+			}
+		}
+		`)
+		ctx := testContextWithoutVariables(query.Operations[0])
+		resp := es.ExecuteQuery(ctx)
+		require.JSONEq(t, `
+		{
+			"__type": {
+				"possibleTypes": [
+				{
+					"name": "Cast"
+				}
+				]
+			}
+		}
+		`, string(resp.Data))
+	})
+
 	t.Run("type referenced only through an interface", func(t *testing.T) {
 		query := gqlparser.MustLoadQuery(es.MergedSchema, `{
 			__type(name: "Cast") {