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Due to the lack of MarshalWrite in the v1 API,
it is unfortunately common to see:
json.NewEncoder(out).Encode(in)
where a single-use Encoder is constructed and thrown away.
This performed acceptably in v1 since every call to Encode
used a globally pooled encoder resource.
Prior to this change, the v1-in-v2 implementation relied
on a bytes.Buffer cached only for the lifetime of the Encoder
object itself. Thus, a single-use Encoder does not benefit.
Modify the wrapper implementation to use the internal
pooled encoder from v2 and use the intermediate buffer
to write directly to the output io.Writer.
We assume that the user-provided io.Writer never leaks the buffer,
but this assumption was already held in the v1 implementation.
We are not increasing the surface area of data corruption risk.
Performance of v1 to v1-in-v2 (before the pool fix):
name old time/op new time/op delta
NewEncoderEncode-32 30.2ms ± 4% 28.3ms ± 9% -6.19% (p=0.002 n=9+10)
name old alloc/op new alloc/op delta
NewEncoderEncode-32 7.64MB ± 0% 28.37MB ± 0% +271.23% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
NewEncoderEncode-32 200k ± 0% 100k ± 0% -49.99% (p=0.000 n=9+10)
Interestingly, v1-in-2 is slightly faster,
but the amount of allocated memory is massive.
Performance of v1 to v1-in-v2 (after the pool fix):
name old time/op new time/op delta
NewEncoderEncode-32 30.2ms ± 4% 24.0ms ± 7% -20.36% (p=0.000 n=9+10)
name old alloc/op new alloc/op delta
NewEncoderEncode-32 7.64MB ± 0% 4.09MB ± 3% -46.52% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
NewEncoderEncode-32 200k ± 0% 100k ± 0% -50.00% (p=0.000 n=9+9)
Now, the v1-in-v2 implementation is better than v1 on all metrics.
Fixes #75026
Change-Id: I50c975b1d5b8da806e46bc627966b0a39c1817eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/740660
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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Historically, Decoder.More reports true when the next read will
return an error. Adjust the v2 Decoder to follow this behavior.
Fixes #76467
Change-Id: I03bfa391e4e89ada8ca869db43c1d0bb63cc0413
Reviewed-on: https://go-review.googlesource.com/c/go/+/728300
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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The Decoder.InputOffset method was always ambiguous about the exact
offset returned since anything between the end of the previous token
to the start of the next token could be a valid result.
Empirically, it seems that the behavior was to report
the end of the previous token unless Decoder.More is called,
in which case it reports the start of the next token.
This is an odd semantic since a relatively side-effect free method
like More is not quite so side-effect free.
However, our goal is to preserve historical v1 semantic when possible
regardless of whether it made sense.
Note that jsontext.Decoder.InputOffset consistently always reports
the end of the previous token. Users can explicitly choose the
exact position they want by inspecting the UnreadBuffer.
Fixes #75468
Change-Id: I1e946e83c9d29dfc09f2913ff8d6b2b80632f292
Reviewed-on: https://go-review.googlesource.com/c/go/+/703856
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
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The jsontext.Decoder.ReadToken method reports a non-EOF error,
if the token stream is truncated and does not form a valid JSON value.
In contrast, the v1 json.Decoder.Token method would report EOF
so long as the input was a prefix of some valid JSON value.
Modify json.Decoder.Token to preserve historical behavior.
This only modifies code that is compiled in under goexperiment.jsonv2.
Updates #69449
Fixes #74750
Change-Id: Ifd281c46f118f0e748076013fefc7659f77c56ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/689516
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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In the event that the input is just JSON whitespace,
the underlying jsontext.Decoder treats this as an empty stream
and reports io.EOF.
The logic in unmarshalFull simply casted io.EOF as io.ErrUnexpectedEOF,
which is inconsistent with how all other io.ErrUnexpectedEOF are reported,
which are wrapped within a jsontext.SyntacticError.
Do the same thing for consistency.
We add a v1 test (without goexperiment.jsonv2) to verify that
the behavior is identical to how v1 has always behaved.
We add a v1in2 test (with goexperiment.jsonv2) to verify that
the v1in2 behavior correctly replicates historical v1 behavior.
We also fix a faulty check in v1 Decoder.Decode,
where it tried to detect errUnexpectedEnd and
return an unwrapped io.ErrUnexpectedEOF error.
This is the exact semantic that v1 has always done
in streaming Decoder.Decode (but not non-streaming Unmarshal).
There is a prior bug reported in #25956 about this inconsistency,
but we aim to preserve historical v1 behavior to reduce
the probability of churn when v1 is re-implemented in terms of v2.
Fixes #74548
Change-Id: Ibca52c3699ff3c09141e081c85f853781a86ec8e
Reviewed-on: https://go-review.googlesource.com/c/go/+/687115
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
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This imports the proposed new v2 JSON API implemented in
github.com/go-json-experiment/json as of commit
d3c622f1b874954c355e60c8e6b6baa5f60d2fed.
When GOEXPERIMENT=jsonv2 is set, the encoding/json/v2 and
encoding/jsontext packages are visible, the encoding/json
package is implemented in terms of encoding/json/v2, and
the encoding/json package include various additional APIs.
(See #71497 for details.)
When GOEXPERIMENT=jsonv2 is not set, the new API is not
present and the encoding/json package is unchanged.
The experimental API is not bound by the Go compatibility
promise and is expected to evolve as updates are made to
the json/v2 proposal.
The contents of encoding/json/internal/jsontest/testdata
are compressed with zstd v1.5.7 with the -19 option.
Fixes #71845
For #71497
Change-Id: Ib8c94e5f0586b6aaa22833190b41cf6ef59f4f01
Reviewed-on: https://go-review.googlesource.com/c/go/+/665796
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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