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#74322 MarshallJSONTo: Skip fields when marshalling to json #180

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60 changes: 60 additions & 0 deletions arshal_default.go
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Original file line number Diff line number Diff line change
Expand Up @@ -786,6 +786,9 @@ func makeMapArshaler(t reflect.Type) *arshaler {
k.SetIterKey(iter)
err := marshalKey(enc, k, mo)
if err != nil {
if errors.Is(err, errSkipMember) {
continue
}
if mo.Flags.Get(jsonflags.CallMethodsWithLegacySemantics) &&
errors.Is(err, jsontext.ErrNonStringName) && nillableLegacyKey && k.IsNil() {
err = enc.WriteToken(jsontext.String(""))
Expand All @@ -799,6 +802,14 @@ func makeMapArshaler(t reflect.Type) *arshaler {
}
v.SetIterValue(iter)
if err := marshalVal(enc, v, mo); err != nil {
if errors.Is(err, errSkipMember) {
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixString(xe.Buf)
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixByte(xe.Buf, ',')
xe.Tokens.Last--
continue
}
return err
}
}
Expand All @@ -817,6 +828,14 @@ func makeMapArshaler(t reflect.Type) *arshaler {
k.SetString(name)
v.Set(va.MapIndex(k.Value))
if err := marshalVal(enc, v, mo); err != nil {
if errors.Is(err, errSkipMember) {
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixString(xe.Buf)
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixByte(xe.Buf, ',')
xe.Tokens.Last--
continue
}
return err
}
}
Expand All @@ -838,6 +857,9 @@ func makeMapArshaler(t reflect.Type) *arshaler {
v.SetIterValue(iter)
err := marshalKey(enc, k, mo)
if err != nil {
if errors.Is(err, errSkipMember) {
continue
}
if mo.Flags.Get(jsonflags.CallMethodsWithLegacySemantics) &&
errors.Is(err, jsontext.ErrNonStringName) && nillableLegacyKey && k.IsNil() {
err = enc.WriteToken(jsontext.String(""))
Expand All @@ -863,6 +885,14 @@ func makeMapArshaler(t reflect.Type) *arshaler {
return err
}
if err := marshalVal(enc, member.val, mo); err != nil {
if errors.Is(err, errSkipMember) {
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixString(xe.Buf)
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixByte(xe.Buf, ',')
xe.Tokens.Last--
continue
}
return err
}
}
Expand Down Expand Up @@ -979,6 +1009,10 @@ func makeMapArshaler(t reflect.Type) *arshaler {
seen.SetMapIndex(k.Value, reflect.Zero(emptyStructType))
}
if err != nil {
if errors.Is(err, errSkipMember) {
dec.ReadToken()
continue
}
if isFatalError(err, uo.Flags) {
return err
}
Expand Down Expand Up @@ -1141,6 +1175,14 @@ func makeStructArshaler(t reflect.Type) *arshaler {
mo.Flags = flagsOriginal
mo.Format = ""
if err != nil {
if errors.Is(err, errSkipMember) {
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixString(xe.Buf)
xe.Buf = jsonwire.TrimSuffixWhitespace(xe.Buf)
xe.Buf = jsonwire.TrimSuffixByte(xe.Buf, ',')
xe.Tokens.Last--
continue
}
return err
}

Expand Down Expand Up @@ -1304,6 +1346,10 @@ func makeStructArshaler(t reflect.Type) *arshaler {
uo.Flags = flagsOriginal
uo.Format = ""
if err != nil {
if errors.Is(err, errSkipMember) {
dec.ReadToken()
continue // skip member
}
if isFatalError(err, uo.Flags) {
return err
}
Expand Down Expand Up @@ -1444,6 +1490,9 @@ func makeSliceArshaler(t reflect.Type) *arshaler {
for i := range n {
v := addressableValue{va.Index(i), false} // indexed slice element is always addressable
if err := marshal(enc, v, mo); err != nil {
if errors.Is(err, errSkipMember) {
continue
}
return err
}
}
Expand Down Expand Up @@ -1499,6 +1548,10 @@ func makeSliceArshaler(t reflect.Type) *arshaler {
v.SetZero()
}
if err := unmarshal(dec, v, uo); err != nil {
if errors.Is(err, errSkipMember) {
dec.ReadToken()
continue // skip member
}
if isFatalError(err, uo.Flags) {
va.SetLen(i)
return err
Expand Down Expand Up @@ -1550,6 +1603,9 @@ func makeArrayArshaler(t reflect.Type) *arshaler {
for i := range n {
v := addressableValue{va.Index(i), va.forcedAddr} // indexed array element is addressable if array is addressable
if err := marshal(enc, v, mo); err != nil {
if errors.Is(err, errSkipMember) {
continue
}
return err
}
}
Expand Down Expand Up @@ -1595,6 +1651,10 @@ func makeArrayArshaler(t reflect.Type) *arshaler {
v.SetZero()
}
if err := unmarshal(dec, v, uo); err != nil {
if errors.Is(err, errSkipMember) {
dec.ReadToken()
continue // skip member
}
if isFatalError(err, uo.Flags) {
return err
}
Expand Down
8 changes: 8 additions & 0 deletions arshal_funcs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,14 @@ import (
// [jsontext.Encoder.WriteToken] since such methods mutate the state.
var SkipFunc = errors.New("json: skip function")

// SkipMember may be returned by [MarshalToFunc] and [UnmarshalFromFunc] functions.
//
// Any function that returns SkipMember must not cause observable side effects
// on the provided [jsontext.Encoder] or [jsontext.Decoder].
// When a member (json property) is skipped, the corresponding member name (key name)
// is also removed from the byte stream.
var errSkipMember = errors.New("json: skip member")

var errSkipMutation = errors.New("must not read or write any tokens when skipping")
var errNonSingularValue = errors.New("must read or write exactly one value")

Expand Down
6 changes: 6 additions & 0 deletions arshal_methods.go
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Original file line number Diff line number Diff line change
Expand Up @@ -193,6 +193,9 @@ func makeMethodArshaler(fncs *arshaler, t reflect.Type) *arshaler {
prevDepth, prevLength := xe.Tokens.DepthLength()
xe.Flags.Set(jsonflags.WithinArshalCall | 1)
err := va.Addr().Interface().(MarshalerTo).MarshalJSONTo(enc)
if errors.Is(err, errSkipMember) { // should this apply to v1 and v2?
return err
}
xe.Flags.Set(jsonflags.WithinArshalCall | 0)
currDepth, currLength := xe.Tokens.DepthLength()
if (prevDepth != currDepth || prevLength+1 != currLength) && err == nil {
Expand Down Expand Up @@ -283,6 +286,9 @@ func makeMethodArshaler(fncs *arshaler, t reflect.Type) *arshaler {
prevDepth, prevLength := xd.Tokens.DepthLength()
xd.Flags.Set(jsonflags.WithinArshalCall | 1)
err := va.Addr().Interface().(UnmarshalerFrom).UnmarshalJSONFrom(dec)
if errors.Is(err, errSkipMember) {
return err
}
xd.Flags.Set(jsonflags.WithinArshalCall | 0)
currDepth, currLength := xd.Tokens.DepthLength()
if (prevDepth != currDepth || prevLength+1 != currLength) && err == nil {
Expand Down
149 changes: 149 additions & 0 deletions arshal_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -560,6 +560,16 @@ type (
pointerAlwaysZero string
pointerNeverZero string

skipStruct struct {
namedString string
}
skipString string
skipInt int
skipFloat64 float64
skipBool bool
skipMap map[string]string
skipSlice []string

valueStringer struct{}
pointerStringer struct{}

Expand Down Expand Up @@ -698,6 +708,49 @@ func addr[T any](v T) *T {
return &v
}

func (*skipString) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipString) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}
func (*skipInt) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipInt) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}
func (*skipFloat64) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipFloat64) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}
func (*skipBool) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipBool) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}
func (*skipStruct) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipStruct) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}
func (*skipMap) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipMap) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}
func (*skipSlice) MarshalJSONTo(enc *jsontext.Encoder) error {
return errSkipMember
}
func (*skipSlice) UnmarshalJSONFrom(*jsontext.Decoder) error {
return errSkipMember
}

func mustParseTime(layout, value string) time.Time {
t, err := time.Parse(layout, value)
if err != nil {
Expand Down Expand Up @@ -4544,6 +4597,60 @@ func TestMarshal(t *testing.T) {
opts: []Options{invalidFormatOption},
in: time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC),
want: `"2000-01-01T00:00:00Z"`,
}, {
name: jsontest.Name("Skip/Struct"),
in: skipStruct{
namedString: "this is a named string",
},
want: ``,
wantErr: errSkipMember,
}, {
name: jsontest.Name("Skip/StructMember"),
in: struct {
X1 string
Y1 skipString
X2 int
Y2 skipInt
X3 float64
Y3 skipFloat64
X4 bool
Y4 skipBool
}{
"this is X",
"skipString",
5,
5,
0.123,
0.123,
true,
true,
},
want: `{"X1":"this is X","X2":5,"X3":0.123,"X4":true}`,
}, {
name: jsontest.Name("Skip/Map"),
in: struct {
skipMap
}{
skipMap{"hello": "world"},
},
want: ``,
wantErr: errSkipMember,
}, {
name: jsontest.Name("Skip/MapMember"),
in: map[string]any{
"X1": "X1 should be visible",
"X2": skipString("X2 should not be visible"),
},
want: `{"X1":"X1 should be visible"}`,
}, {
name: jsontest.Name("Skip/Slice"),
in: skipSlice{"hello", "world!"},
want: "",
wantErr: errSkipMember,
}, {
name: jsontest.Name("Skip/SliceMember"),
in: []any{"Visible", skipString("Hidden")},
want: "[\"Visible\"]",
}}

for _, tt := range tests {
Expand Down Expand Up @@ -9110,6 +9217,48 @@ func TestUnmarshal(t *testing.T) {
inBuf: `"2000-01-01T00:00:00Z"`,
inVal: addr(time.Time{}),
want: addr(time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)),
}, {
name: jsontest.Name("Skip/Struct"),
inBuf: `{"X":"this is namedString"}`,
inVal: new(skipStruct),
want: addr(skipStruct{}),
wantErr: errSkipMember,
}, {
name: jsontest.Name("Skip/StructMember"),
inBuf: `{"X":"hello", "Y": "should not show"}`,
inVal: new(struct {
X string
Y skipString
}),
want: addr(struct {
X string
Y skipString
}{X: "hello"}),
}, {
name: jsontest.Name("Skip/MapMember"),
inBuf: `{"K1":"hello", "K2": "this is wrong", "K3": 3}`,
inVal: addr(map[string]any{
"K1": string("should not show"),
"K2": skipString("this is correct"),
"K3": 0,
}),
want: addr(map[string]any{
"K1": string("hello"),
"K2": skipString("this is correct"),
"K3": 3,
}),
}, {
name: jsontest.Name("Skip/ArrayMember"),
inBuf: `["X", "Y", "Z"]`,
inVal: addr([]skipString{}),
// using make is needed to solve issue
// *[]json.skipString, &[%!t(json.skipString=) %!t(json.skipString=) %!t(json.skipString=)]
want: addr(make([]skipString, 3)),
}, {
name: jsontest.Name("Skip/SliceMember"),
inBuf: `["X", "Y", "Z"]`,
inVal: addr([]skipString{}),
want: addr(make([]skipString, 3)),
}}

for _, tt := range tests {
Expand Down