encoding/json: support encoding.TextMarshaler, encoding.TextUnmarshaler

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12703043

src/pkg/encoding/json/decode.go

@@ -8,6 +8,7 @@
 package json
 
 import (
+	"encoding"
 	"encoding/base64"
 	"errors"
 	"fmt"
@@ -293,7 +294,7 @@ func (d *decodeState) value(v reflect.Value) {
 // until it gets to a non-pointer.
 // if it encounters an Unmarshaler, indirect stops and returns that.
 // if decodingNull is true, indirect stops at the last pointer so it can be set to nil.
-func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, reflect.Value) {
+func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
 	// If v is a named type and is addressable,
 	// start with its address, so that if the type has pointer methods,
 	// we find them.
@@ -322,28 +323,38 @@ func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler,
 			v.Set(reflect.New(v.Type().Elem()))
 		}
 		if v.Type().NumMethod() > 0 {
-			if unmarshaler, ok := v.Interface().(Unmarshaler); ok {
-				return unmarshaler, reflect.Value{}
+			if u, ok := v.Interface().(Unmarshaler); ok {
+				return u, nil, reflect.Value{}
+			}
+			if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
+				return nil, u, reflect.Value{}
 			}
 		}
 		v = v.Elem()
 	}
-	return nil, v
+	return nil, nil, v
 }
 
 // array consumes an array from d.data[d.off-1:], decoding into the value v.
 // the first byte of the array ('[') has been read already.
 func (d *decodeState) array(v reflect.Value) {
 	// Check for unmarshaler.
-	unmarshaler, pv := d.indirect(v, false)
-	if unmarshaler != nil {
+	u, ut, pv := d.indirect(v, false)
+	if u != nil {
 		d.off--
-		err := unmarshaler.UnmarshalJSON(d.next())
+		err := u.UnmarshalJSON(d.next())
 		if err != nil {
 			d.error(err)
 		}
 		return
 	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"array", v.Type()})
+		d.off--
+		d.next()
+		return
+	}
+
 	v = pv
 
 	// Check type of target.
@@ -434,15 +445,21 @@ func (d *decodeState) array(v reflect.Value) {
 // the first byte of the object ('{') has been read already.
 func (d *decodeState) object(v reflect.Value) {
 	// Check for unmarshaler.
-	unmarshaler, pv := d.indirect(v, false)
-	if unmarshaler != nil {
+	u, ut, pv := d.indirect(v, false)
+	if u != nil {
 		d.off--
-		err := unmarshaler.UnmarshalJSON(d.next())
+		err := u.UnmarshalJSON(d.next())
 		if err != nil {
 			d.error(err)
 		}
 		return
 	}
+	if ut != nil {
+		d.saveError(&UnmarshalTypeError{"object", v.Type()})
+		d.off--
+		d.next() // skip over { } in input
+		return
+	}
 	v = pv
 
 	// Decoding into nil interface?  Switch to non-reflect code.
@@ -611,14 +628,37 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 		return
 	}
 	wantptr := item[0] == 'n' // null
-	unmarshaler, pv := d.indirect(v, wantptr)
-	if unmarshaler != nil {
-		err := unmarshaler.UnmarshalJSON(item)
+	u, ut, pv := d.indirect(v, wantptr)
+	if u != nil {
+		err := u.UnmarshalJSON(item)
 		if err != nil {
 			d.error(err)
 		}
 		return
 	}
+	if ut != nil {
+		if item[0] != '"' {
+			if fromQuoted {
+				d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.saveError(&UnmarshalTypeError{"string", v.Type()})
+			}
+		}
+		s, ok := unquoteBytes(item)
+		if !ok {
+			if fromQuoted {
+				d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
+			} else {
+				d.error(errPhase)
+			}
+		}
+		err := ut.UnmarshalText(s)
+		if err != nil {
+			d.error(err)
+		}
+		return
+	}
+
 	v = pv
 
 	switch c := item[0]; c {

src/pkg/encoding/json/decode_test.go

@@ -6,6 +6,7 @@ package json
 
 import (
 	"bytes"
+	"encoding"
 	"fmt"
 	"image"
 	"reflect"
@@ -57,7 +58,7 @@ type unmarshaler struct {
 }
 
 func (u *unmarshaler) UnmarshalJSON(b []byte) error {
-	*u = unmarshaler{true} // All we need to see that UnmarshalJson is called.
+	*u = unmarshaler{true} // All we need to see that UnmarshalJSON is called.
 	return nil
 }
 
@@ -65,6 +66,26 @@ type ustruct struct {
 	M unmarshaler
 }
 
+type unmarshalerText struct {
+	T bool
+}
+
+// needed for re-marshaling tests
+func (u *unmarshalerText) MarshalText() ([]byte, error) {
+	return []byte(""), nil
+}
+
+func (u *unmarshalerText) UnmarshalText(b []byte) error {
+	*u = unmarshalerText{true} // All we need to see that UnmarshalText is called.
+	return nil
+}
+
+var _ encoding.TextUnmarshaler = (*unmarshalerText)(nil)
+
+type ustructText struct {
+	M unmarshalerText
+}
+
 var (
 	um0, um1 unmarshaler // target2 of unmarshaling
 	ump      = &um1
@@ -72,6 +93,13 @@ var (
 	umslice  = []unmarshaler{{true}}
 	umslicep = new([]unmarshaler)
 	umstruct = ustruct{unmarshaler{true}}
+
+	um0T, um1T unmarshalerText // target2 of unmarshaling
+	umpT       = &um1T
+	umtrueT    = unmarshalerText{true}
+	umsliceT   = []unmarshalerText{{true}}
+	umslicepT  = new([]unmarshalerText)
+	umstructT  = ustructText{unmarshalerText{true}}
 )
 
 // Test data structures for anonymous fields.
@@ -261,6 +289,13 @@ var unmarshalTests = []unmarshalTest{
 	{in: `[{"T":false}]`, ptr: &umslicep, out: &umslice},
 	{in: `{"M":{"T":false}}`, ptr: &umstruct, out: umstruct},
 
+	// UnmarshalText interface test
+	{in: `"X"`, ptr: &um0T, out: umtrueT}, // use "false" so test will fail if custom unmarshaler is not called
+	{in: `"X"`, ptr: &umpT, out: &umtrueT},
+	{in: `["X"]`, ptr: &umsliceT, out: umsliceT},
+	{in: `["X"]`, ptr: &umslicepT, out: &umsliceT},
+	{in: `{"M":"X"}`, ptr: &umstructT, out: umstructT},
+
 	{
 		in: `{
 			"Level0": 1,
@@ -505,7 +540,7 @@ func TestUnmarshal(t *testing.T) {
 				dec.UseNumber()
 			}
 			if err := dec.Decode(vv.Interface()); err != nil {
-				t.Errorf("#%d: error re-unmarshaling: %v", i, err)
+				t.Errorf("#%d: error re-unmarshaling %#q: %v", i, enc, err)
 				continue
 			}
 			if !reflect.DeepEqual(v.Elem().Interface(), vv.Elem().Interface()) {
@@ -979,15 +1014,20 @@ func TestRefUnmarshal(t *testing.T) {
 		// Ref is defined in encode_test.go.
 		R0 Ref
 		R1 *Ref
+		R2 RefText
+		R3 *RefText
 	}
 	want := S{
 		R0: 12,
 		R1: new(Ref),
+		R2: 13,
+		R3: new(RefText),
 	}
 	*want.R1 = 12
+	*want.R3 = 13
 
 	var got S
-	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref"}`), &got); err != nil {
+	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref","R2":"ref","R3":"ref"}`), &got); err != nil {
 		t.Fatalf("Unmarshal: %v", err)
 	}
 	if !reflect.DeepEqual(got, want) {

src/pkg/encoding/json/encode.go

@@ -12,6 +12,7 @@ package json
 
 import (
 	"bytes"
+	"encoding"
 	"encoding/base64"
 	"math"
 	"reflect"
@@ -361,17 +362,29 @@ func newTypeEncoder(t reflect.Type, vx reflect.Value) encoderFunc {
 	if !vx.IsValid() {
 		vx = reflect.New(t).Elem()
 	}
+
 	_, ok := vx.Interface().(Marshaler)
 	if ok {
-		return valueIsMarshallerEncoder
+		return marshalerEncoder
 	}
-	// T doesn't match the interface. Check against *T too.
 	if vx.Kind() != reflect.Ptr && vx.CanAddr() {
 		_, ok = vx.Addr().Interface().(Marshaler)
 		if ok {
-			return valueAddrIsMarshallerEncoder
+			return addrMarshalerEncoder
 		}
 	}
+
+	_, ok = vx.Interface().(encoding.TextMarshaler)
+	if ok {
+		return textMarshalerEncoder
+	}
+	if vx.Kind() != reflect.Ptr && vx.CanAddr() {
+		_, ok = vx.Addr().Interface().(encoding.TextMarshaler)
+		if ok {
+			return addrTextMarshalerEncoder
+		}
+	}
+
 	switch vx.Kind() {
 	case reflect.Bool:
 		return boolEncoder
@@ -406,7 +419,7 @@ func invalidValueEncoder(e *encodeState, v reflect.Value, quoted bool) {
 	e.WriteString("null")
 }
 
-func valueIsMarshallerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+func marshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
 	if v.Kind() == reflect.Ptr && v.IsNil() {
 		e.WriteString("null")
 		return
@@ -422,9 +435,9 @@ func valueIsMarshallerEncoder(e *encodeState, v reflect.Value, quoted bool) {
 	}
 }
 
-func valueAddrIsMarshallerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+func addrMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
 	va := v.Addr()
-	if va.Kind() == reflect.Ptr && va.IsNil() {
+	if va.IsNil() {
 		e.WriteString("null")
 		return
 	}
@@ -439,6 +452,37 @@ func valueAddrIsMarshallerEncoder(e *encodeState, v reflect.Value, quoted bool)
 	}
 }
 
+func textMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := v.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err == nil {
+		_, err = e.stringBytes(b)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
+func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err == nil {
+		_, err = e.stringBytes(b)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err})
+	}
+}
+
 func boolEncoder(e *encodeState, v reflect.Value, quoted bool) {
 	if quoted {
 		e.WriteByte('"')
@@ -728,6 +772,7 @@ func (sv stringValues) Swap(i, j int)      { sv[i], sv[j] = sv[j], sv[i] }
 func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
 func (sv stringValues) get(i int) string   { return sv[i].String() }
 
+// NOTE: keep in sync with stringBytes below.
 func (e *encodeState) string(s string) (int, error) {
 	len0 := e.Len()
 	e.WriteByte('"')
@@ -800,6 +845,79 @@ func (e *encodeState) string(s string) (int, error) {
 	return e.Len() - len0, nil
 }
 
+// NOTE: keep in sync with string above.
+func (e *encodeState) stringBytes(s []byte) (int, error) {
+	len0 := e.Len()
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' && b != '&' {
+				i++
+				continue
+			}
+			if start < i {
+				e.Write(s[start:i])
+			}
+			switch b {
+			case '\\', '"':
+				e.WriteByte('\\')
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('\\')
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('\\')
+				e.WriteByte('r')
+			default:
+				// This encodes bytes < 0x20 except for \n and \r,
+				// as well as < and >. The latter are escaped because they
+				// can lead to security holes when user-controlled strings
+				// are rendered into JSON and served to some browsers.
+				e.WriteString(`\u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRune(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.Write(s[start:])
+	}
+	e.WriteByte('"')
+	return e.Len() - len0, nil
+}
+
 // A field represents a single field found in a struct.
 type field struct {
 	name      string

src/pkg/encoding/json/encode_test.go

@@ -9,6 +9,7 @@ import (
 	"math"
 	"reflect"
 	"testing"
+	"unicode"
 )
 
 type Optionals struct {
@@ -146,19 +147,46 @@ func (Val) MarshalJSON() ([]byte, error) {
 	return []byte(`"val"`), nil
 }
 
+// RefText has Marshaler and Unmarshaler methods with pointer receiver.
+type RefText int
+
+func (*RefText) MarshalText() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *RefText) UnmarshalText([]byte) error {
+	*r = 13
+	return nil
+}
+
+// ValText has Marshaler methods with value receiver.
+type ValText int
+
+func (ValText) MarshalText() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
 func TestRefValMarshal(t *testing.T) {
 	var s = struct {
 		R0 Ref
 		R1 *Ref
+		R2 RefText
+		R3 *RefText
 		V0 Val
 		V1 *Val
+		V2 ValText
+		V3 *ValText
 	}{
 		R0: 12,
 		R1: new(Ref),
+		R2: 14,
+		R3: new(RefText),
 		V0: 13,
 		V1: new(Val),
+		V2: 15,
+		V3: new(ValText),
 	}
-	const want = `{"R0":"ref","R1":"ref","V0":"val","V1":"val"}`
+	const want = `{"R0":"ref","R1":"ref","R2":"\"ref\"","R3":"\"ref\"","V0":"val","V1":"val","V2":"\"val\"","V3":"\"val\""}`
 	b, err := Marshal(&s)
 	if err != nil {
 		t.Fatalf("Marshal: %v", err)
@@ -175,15 +203,32 @@ func (C) MarshalJSON() ([]byte, error) {
 	return []byte(`"<&>"`), nil
 }
 
+// CText implements Marshaler and returns unescaped text.
+type CText int
+
+func (CText) MarshalText() ([]byte, error) {
+	return []byte(`"<&>"`), nil
+}
+
 func TestMarshalerEscaping(t *testing.T) {
 	var c C
-	const want = `"\u003c\u0026\u003e"`
+	want := `"\u003c\u0026\u003e"`
 	b, err := Marshal(c)
 	if err != nil {
-		t.Fatalf("Marshal: %v", err)
+		t.Fatalf("Marshal(c): %v", err)
 	}
 	if got := string(b); got != want {
-		t.Errorf("got %q, want %q", got, want)
+		t.Errorf("Marshal(c) = %#q, want %#q", got, want)
+	}
+
+	var ct CText
+	want = `"\"\u003c\u0026\u003e\""`
+	b, err = Marshal(ct)
+	if err != nil {
+		t.Fatalf("Marshal(ct): %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("Marshal(ct) = %#q, want %#q", got, want)
 	}
 }
 
@@ -310,3 +355,49 @@ func TestDuplicatedFieldDisappears(t *testing.T) {
 		t.Fatalf("Marshal: got %s want %s", got, want)
 	}
 }
+
+func TestStringBytes(t *testing.T) {
+	// Test that encodeState.stringBytes and encodeState.string use the same encoding.
+	es := &encodeState{}
+	var r []rune
+	for i := '\u0000'; i <= unicode.MaxRune; i++ {
+		r = append(r, i)
+	}
+	s := string(r) + "\xff\xff\xffhello" // some invalid UTF-8 too
+	_, err := es.string(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	esBytes := &encodeState{}
+	_, err = esBytes.stringBytes([]byte(s))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	enc := es.Buffer.String()
+	encBytes := esBytes.Buffer.String()
+	if enc != encBytes {
+		i := 0
+		for i < len(enc) && i < len(encBytes) && enc[i] == encBytes[i] {
+			i++
+		}
+		enc = enc[i:]
+		encBytes = encBytes[i:]
+		i = 0
+		for i < len(enc) && i < len(encBytes) && enc[len(enc)-i-1] == encBytes[len(encBytes)-i-1] {
+			i++
+		}
+		enc = enc[:len(enc)-i]
+		encBytes = encBytes[:len(encBytes)-i]
+
+		if len(enc) > 20 {
+			enc = enc[:20] + "..."
+		}
+		if len(encBytes) > 20 {
+			encBytes = encBytes[:20] + "..."
+		}
+
+		t.Errorf("encodings differ at %#q vs %#q", enc, encBytes)
+	}
+}