Merge pull request #302 from fadi-alkatut/master

Validate types are including all fields from implemented interface(s)

internal/schema/schema.go

@@ -291,6 +291,11 @@ func (s *Schema) Parse(schemaString string, useStringDescriptions bool) error {
 			if !ok {
 				return errors.Errorf("type %q is not an interface", intfName)
 			}
+			for _, f := range intf.Fields.Names() {
+				if obj.Fields.Get(f) == nil {
+					return errors.Errorf("interface %q expects field %q but %q does not provide it", intfName, f, obj.Name)
+				}
+			}
 			obj.Interfaces[i] = intf
 			intf.PossibleTypes = append(intf.PossibleTypes, obj)
 		}

internal/schema/schema_test.go

@@ -3,6 +3,7 @@ package schema_test
 import (
 	"testing"
 
+	"github.com/graph-gophers/graphql-go/errors"
 	"github.com/graph-gophers/graphql-go/internal/schema"
 )
 
@@ -89,3 +90,25 @@ func TestParse(t *testing.T) {
 		})
 	}
 }
+
+func TestInvalidInterfaceImpl(t *testing.T) {
+	var tests = []parseTestCase{{
+		description: "Parses type Welcome that implements interface Greeting without providing required fields",
+		sdl:         "interface Greeting { message: String! } type Welcome implements Greeting {}",
+		err:         errors.Errorf(`interface "Greeting" expects field "message" but "Welcome" does not provide it`),
+	}}
+
+	setup := func(t *testing.T) *schema.Schema {
+		t.Helper()
+		return schema.New()
+	}
+	for _, test := range tests {
+		t.Run(test.description, func(t *testing.T) {
+			schema := setup(t)
+			err := schema.Parse(test.sdl, false)
+			if err == nil || err.Error() != test.err.Error() {
+				t.Fatal(err)
+			}
+		})
+	}
+}