Allow omitted non-null arguments when a default value exists (#7)

definition.go

@@ -656,6 +656,13 @@ func (st *Argument) Error() error {
 	return nil
 }
 
+// IsRequired returns if an argument is required,
+// i.e. cannot be omitted.
+func (st *Argument) IsRequired() bool {
+	_, isOfTypeNonNull := st.Type.(*NonNull)
+	return isOfTypeNonNull && st.DefaultValue == nil
+}
+
 // Interface Type Definition
 //
 // When a field can return one of a heterogeneous set of types, a Interface type

rules.go

@@ -1271,15 +1271,15 @@ func ProvidedNonNullArgumentsRule(context *ValidationContext) *ValidationRuleIns
 						for _, argDef := range fieldDef.Args {
 							argAST, _ := argASTMap[argDef.Name()]
 							if argAST == nil {
-								if argDefType, ok := argDef.Type.(*NonNull); ok {
+								if argDef.IsRequired() {
 									fieldName := ""
 									if fieldAST.Name != nil {
 										fieldName = fieldAST.Name.Value
 									}
 									reportError(
 										context,
 										fmt.Sprintf(`Field "%v" argument "%v" of type "%v" `+
-											`is required but not provided.`, fieldName, argDef.Name(), argDefType),
+											`is required but not provided.`, fieldName, argDef.Name(), argDef.Type),
 										[]ast.Node{fieldAST},
 									)
 								}
@@ -1312,15 +1312,15 @@ func ProvidedNonNullArgumentsRule(context *ValidationContext) *ValidationRuleIns
 						for _, argDef := range directiveDef.Args {
 							argAST, _ := argASTMap[argDef.Name()]
 							if argAST == nil {
-								if argDefType, ok := argDef.Type.(*NonNull); ok {
+								if argDef.IsRequired() {
 									directiveName := ""
 									if directiveAST.Name != nil {
 										directiveName = directiveAST.Name.Value
 									}
 									reportError(
 										context,
 										fmt.Sprintf(`Directive "@%v" argument "%v" of type `+
-											`"%v" is required but not provided.`, directiveName, argDef.Name(), argDefType),
+											`"%v" is required but not provided.`, directiveName, argDef.Name(), argDef.Type),
 										[]ast.Node{directiveAST},
 									)
 								}

rules_provided_non_null_arguments_test.go

@@ -36,6 +36,24 @@ func TestValidate_ProvidedNonNullArguments_ValidNonNullableValue_NoArgOnOptional
         }
     `)
 }
+func TestValidate_ProvidedNonNullArguments_ValidNonNullableValue_WithDefault(t *testing.T) {
+	testutil.ExpectPassesRule(t, graphql.ProvidedNonNullArgumentsRule, `
+        {
+          complicatedArgs {
+            nonNullFieldWithDefault
+          }
+        }
+    `)
+}
+func TestValidate_ProvidedNonNullArguments_ValidNonNullableValue_WithDefaultAndValue(t *testing.T) {
+	testutil.ExpectPassesRule(t, graphql.ProvidedNonNullArgumentsRule, `
+        {
+          complicatedArgs {
+            nonNullFieldWithDefault(arg:1)
+          }
+        }
+    `)
+}
 func TestValidate_ProvidedNonNullArguments_ValidNonNullableValue_MultipleArgs(t *testing.T) {
 	testutil.ExpectPassesRule(t, graphql.ProvidedNonNullArgumentsRule, `
         {

testutil/rules_test_harness.go

@@ -383,6 +383,15 @@ func init() {
 					},
 				},
 			},
+			"nonNullFieldWithDefault": &graphql.Field{
+				Type: graphql.String,
+				Args: graphql.FieldConfigArgument{
+					"arg": &graphql.ArgumentConfig{
+						Type: graphql.NewNonNull(graphql.Int),
+						DefaultValue: 0,
+					},
+				},
+			},
 			"multipleOpts": &graphql.Field{
 				Type: graphql.String,
 				Args: graphql.FieldConfigArgument{