Support for null values

language/ast/node.go

@@ -26,6 +26,7 @@ var _ Node = (*EnumValue)(nil)
 var _ Node = (*ListValue)(nil)
 var _ Node = (*ObjectValue)(nil)
 var _ Node = (*ObjectField)(nil)
+var _ Node = (*NullValue)(nil)
 var _ Node = (*Directive)(nil)
 var _ Node = (*Named)(nil)
 var _ Node = (*List)(nil)

language/ast/values.go

@@ -19,6 +19,7 @@ var _ Value = (*BooleanValue)(nil)
 var _ Value = (*EnumValue)(nil)
 var _ Value = (*ListValue)(nil)
 var _ Value = (*ObjectValue)(nil)
+var _ Value = (*NullValue)(nil)
 
 // Variable implements Node, Value
 type Variable struct {
@@ -300,3 +301,31 @@ func (f *ObjectField) GetLoc() *Location {
 func (f *ObjectField) GetValue() interface{} {
 	return f.Value
 }
+
+// NullValue implements Node, Value
+type NullValue struct {
+	Kind string
+	Loc  *Location
+}
+
+func (n *NullValue) GetKind() string {
+	return n.Kind
+}
+
+func (n *NullValue) GetLoc() *Location {
+	return n.Loc
+}
+
+func (n *NullValue) GetValue() interface{} {
+	return nil
+}
+
+func NewNullValue(v *NullValue) *NullValue {
+	if v == nil {
+		v = &NullValue{}
+	}
+	return &NullValue{
+		Kind: kinds.NullValue,
+		Loc:  v.Loc,
+	}
+}

language/kinds/kinds.go

@@ -27,6 +27,7 @@ const (
 	ListValue    = "ListValue"
 	ObjectValue  = "ObjectValue"
 	ObjectField  = "ObjectField"
+	NullValue    = "NullValue"
 
 	// Directives
 	Directive = "Directive"

language/parser/parser.go

@@ -606,7 +606,14 @@ func parseValueLiteral(parser *Parser, isConst bool) (ast.Value, error) {
 				Value: value,
 				Loc:   loc(parser, token.Start),
 			}), nil
-		} else if token.Value != "null" {
+		} else if token.Value == "null" {
+			if err := advance(parser); err != nil {
+				return nil, err
+			}
+			return ast.NewNullValue(&ast.NullValue{
+				Loc: loc(parser, token.Start),
+			}), nil
+		} else {
 			if err := advance(parser); err != nil {
 				return nil, err
 			}
@@ -1562,7 +1569,8 @@ func unexpectedEmpty(parser *Parser, beginLoc int, openKind, closeKind lexer.Tok
 	return gqlerrors.NewSyntaxError(parser.Source, beginLoc, description)
 }
 
-//  Returns list of parse nodes, determined by
+//	Returns list of parse nodes, determined by
+//
 // the parseFn. This list begins with a lex token of openKind
 // and ends with a lex token of closeKind. Advances the parser
 // to the next lex token after the closing token.

language/parser/parser_test.go

@@ -183,15 +183,6 @@ func TestDoesNotAcceptFragmentsSpreadOfOn(t *testing.T) {
 	testErrorMessage(t, test)
 }
 
-func TestDoesNotAllowNullAsValue(t *testing.T) {
-	test := errorMessageTest{
-		`{ fieldWithNullableStringInput(input: null) }'`,
-		`Syntax Error GraphQL (1:39) Unexpected Name "null"`,
-		false,
-	}
-	testErrorMessage(t, test)
-}
-
 func TestParsesMultiByteCharacters_Unicode(t *testing.T) {
 
 	doc := `
@@ -498,6 +489,14 @@ func TestParsesEnumValueDefinitionWithDescription(t *testing.T) {
 	}
 }
 
+func TestNullIsAllowedAsValue(t *testing.T) {
+	source := `{ fieldWithNullableStringInput(input: null) }`
+	_, err := Parse(ParseParams{Source: source})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 func TestDefinitionsWithDescriptions(t *testing.T) {
 	testCases := []struct {
 		name            string

language/printer/printer.go

@@ -428,6 +428,16 @@ var printDocASTReducer = map[string]visitor.VisitFunc{
 		}
 		return visitor.ActionNoChange, nil
 	},
+	"NullValue": func(p visitor.VisitFuncParams) (string, interface{}) {
+		const nullStr = "null"
+		switch p.Node.(type) {
+		case *ast.NullValue:
+			return visitor.ActionUpdate, nullStr
+		case map[string]interface{}: //TODO: not sure if this is necessary
+			return visitor.ActionUpdate, nullStr
+		}
+		return visitor.ActionNoChange, nil
+	},
 
 	// Directive
 	"Directive": func(p visitor.VisitFuncParams) (string, interface{}) {

scalars.go

@@ -15,6 +15,9 @@ import (
 // n.b. JavaScript's integers are safe between -(2^53 - 1) and 2^53 - 1 because
 // they are internally represented as IEEE 754 doubles.
 func coerceInt(value interface{}) interface{} {
+	if value == nil {
+		return nil
+	}
 	switch value := value.(type) {
 	case bool:
 		if value == true {
@@ -162,12 +165,17 @@ var Int = NewScalar(ScalarConfig{
 			if intValue, err := strconv.Atoi(valueAST.Value); err == nil {
 				return intValue
 			}
+		case *ast.NullValue:
+			return nil
 		}
 		return nil
 	},
 })
 
 func coerceFloat(value interface{}) interface{} {
+	if value == nil {
+		return nil
+	}
 	switch value := value.(type) {
 	case bool:
 		if value == true {
@@ -299,12 +307,17 @@ var Float = NewScalar(ScalarConfig{
 			if floatValue, err := strconv.ParseFloat(valueAST.Value, 64); err == nil {
 				return floatValue
 			}
+		case *ast.NullValue:
+			return nil
 		}
 		return nil
 	},
 })
 
 func coerceString(value interface{}) interface{} {
+	if value == nil {
+		return nil
+	}
 	if v, ok := value.(*string); ok {
 		if v == nil {
 			return nil
@@ -326,12 +339,17 @@ var String = NewScalar(ScalarConfig{
 		switch valueAST := valueAST.(type) {
 		case *ast.StringValue:
 			return valueAST.Value
+		case *ast.NullValue:
+			return nil
 		}
 		return nil
 	},
 })
 
 func coerceBool(value interface{}) interface{} {
+	if value == nil {
+		return nil
+	}
 	switch value := value.(type) {
 	case bool:
 		return value
@@ -485,6 +503,8 @@ var Boolean = NewScalar(ScalarConfig{
 		switch valueAST := valueAST.(type) {
 		case *ast.BooleanValue:
 			return valueAST.Value
+		case *ast.NullValue:
+			return nil
 		}
 		return nil
 	},
@@ -506,12 +526,17 @@ var ID = NewScalar(ScalarConfig{
 			return valueAST.Value
 		case *ast.StringValue:
 			return valueAST.Value
+		case *ast.NullValue:
+			return nil
 		}
 		return nil
 	},
 })
 
 func serializeDateTime(value interface{}) interface{} {
+	if value == nil {
+		return nil
+	}
 	switch value := value.(type) {
 	case time.Time:
 		buff, err := value.MarshalText()
@@ -531,6 +556,9 @@ func serializeDateTime(value interface{}) interface{} {
 }
 
 func unserializeDateTime(value interface{}) interface{} {
+	if value == nil {
+		return nil
+	}
 	switch value := value.(type) {
 	case []byte:
 		t := time.Time{}
@@ -564,6 +592,8 @@ var DateTime = NewScalar(ScalarConfig{
 		switch valueAST := valueAST.(type) {
 		case *ast.StringValue:
 			return unserializeDateTime(valueAST.Value)
+		case *ast.NullValue:
+			return nil
 		}
 		return nil
 	},