encoding/json/v2: fix UnmarshalDecode regression with EOF

When EOF is encountered within jsontext.Decoder stream without
starting to parse any token, UnmarshalDecode should report EOF,
rather than converting it into ErrUnexpectedEOF.

This fixes a regression introduced by https://go.dev/cl/689919.

This change only affects code compiled under goexperiment.jsonv2.

Fixes #74835

Change-Id: I7e8e57ab11b462c422c538503ed8c6b91ead53bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/692175
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Jake Bailey <jacob.b.bailey@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai 2025-07-31 15:01:47 -07:00 committed by Gopher Robot
parent b096ddb9ea
commit cf4af0b2f3
2 changed files with 47 additions and 2 deletions

View file

@ -470,7 +470,7 @@ func unmarshalDecode(in *jsontext.Decoder, out any, uo *jsonopts.Struct, last bo
// was validated before attempting to unmarshal it.
if uo.Flags.Get(jsonflags.ReportErrorsWithLegacySemantics) {
if err := export.Decoder(in).CheckNextValue(last); err != nil {
if err == io.EOF {
if err == io.EOF && last {
offset := in.InputOffset() + int64(len(in.UnreadBuffer()))
return &jsontext.SyntacticError{ByteOffset: offset, Err: io.ErrUnexpectedEOF}
}
@ -487,7 +487,7 @@ func unmarshalDecode(in *jsontext.Decoder, out any, uo *jsonopts.Struct, last bo
if !uo.Flags.Get(jsonflags.AllowDuplicateNames) {
export.Decoder(in).Tokens.InvalidateDisabledNamespaces()
}
if err == io.EOF {
if err == io.EOF && last {
offset := in.InputOffset() + int64(len(in.UnreadBuffer()))
return &jsontext.SyntacticError{ByteOffset: offset, Err: io.ErrUnexpectedEOF}
}

View file

@ -9413,6 +9413,51 @@ func TestUnmarshalDecodeOptions(t *testing.T) {
}
}
func TestUnmarshalDecodeStream(t *testing.T) {
tests := []struct {
in string
want []any
err error
}{
{in: ``, err: io.EOF},
{in: `{`, err: &jsontext.SyntacticError{ByteOffset: len64(`{`), Err: io.ErrUnexpectedEOF}},
{in: `{"`, err: &jsontext.SyntacticError{ByteOffset: len64(`{"`), Err: io.ErrUnexpectedEOF}},
{in: `{"k"`, err: &jsontext.SyntacticError{ByteOffset: len64(`{"k"`), JSONPointer: "/k", Err: io.ErrUnexpectedEOF}},
{in: `{"k":`, err: &jsontext.SyntacticError{ByteOffset: len64(`{"k":`), JSONPointer: "/k", Err: io.ErrUnexpectedEOF}},
{in: `{"k",`, err: &jsontext.SyntacticError{ByteOffset: len64(`{"k"`), JSONPointer: "/k", Err: jsonwire.NewInvalidCharacterError(",", "after object name (expecting ':')")}},
{in: `{"k"}`, err: &jsontext.SyntacticError{ByteOffset: len64(`{"k"`), JSONPointer: "/k", Err: jsonwire.NewInvalidCharacterError("}", "after object name (expecting ':')")}},
{in: `[`, err: &jsontext.SyntacticError{ByteOffset: len64(`[`), Err: io.ErrUnexpectedEOF}},
{in: `[0`, err: &jsontext.SyntacticError{ByteOffset: len64(`[0`), Err: io.ErrUnexpectedEOF}},
{in: ` [0`, err: &jsontext.SyntacticError{ByteOffset: len64(` [0`), Err: io.ErrUnexpectedEOF}},
{in: `[0.`, err: &jsontext.SyntacticError{ByteOffset: len64(`[`), JSONPointer: "/0", Err: io.ErrUnexpectedEOF}},
{in: `[0. `, err: &jsontext.SyntacticError{ByteOffset: len64(`[0.`), JSONPointer: "/0", Err: jsonwire.NewInvalidCharacterError(" ", "in number (expecting digit)")}},
{in: `[0,`, err: &jsontext.SyntacticError{ByteOffset: len64(`[0,`), Err: io.ErrUnexpectedEOF}},
{in: `[0:`, err: &jsontext.SyntacticError{ByteOffset: len64(`[0`), Err: jsonwire.NewInvalidCharacterError(":", "after array element (expecting ',' or ']')")}},
{in: `n`, err: &jsontext.SyntacticError{ByteOffset: len64(`n`), Err: io.ErrUnexpectedEOF}},
{in: `nul`, err: &jsontext.SyntacticError{ByteOffset: len64(`nul`), Err: io.ErrUnexpectedEOF}},
{in: `fal `, err: &jsontext.SyntacticError{ByteOffset: len64(`fal`), Err: jsonwire.NewInvalidCharacterError(" ", "in literal false (expecting 's')")}},
{in: `false`, want: []any{false}, err: io.EOF},
{in: `false0.0[]null`, want: []any{false, 0.0, []any{}, nil}, err: io.EOF},
}
for _, tt := range tests {
d := jsontext.NewDecoder(strings.NewReader(tt.in))
var got []any
for {
var v any
if err := UnmarshalDecode(d, &v); err != nil {
if !reflect.DeepEqual(err, tt.err) {
t.Errorf("`%s`: UnmarshalDecode error = %v, want %v", tt.in, err, tt.err)
}
break
}
got = append(got, v)
}
if !reflect.DeepEqual(got, tt.want) {
t.Errorf("`%s`: UnmarshalDecode = %v, want %v", tt.in, got, tt.want)
}
}
}
// BenchmarkUnmarshalDecodeOptions is a minimal decode operation to measure
// the overhead options setup before the unmarshal operation.
func BenchmarkUnmarshalDecodeOptions(b *testing.B) {