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2025-07-14encoding/json: decompose legacy optionsJoe Tsai
WARNING: This commit contains breaking changes for those already using GOEXPERIMENT=jsonv2. This decomposes FormatBytesWithLegacySemantics as: * FormatBytesWithLegacySemantics * FormatByteArrayAsArray * ParseBytesWithLooseRFC4648 This decomposes FormatTimeWithLegacySemantics as: * FormatDurationAsNano * ParseTimeWithLooseRFC3339 In particular, it splits out specific behaviors from the option that may need to be specified on a finer-grain level. FormatByteArrayAsArray and FormatDurationAsNano are targeted to just the default representation of a [N]byte or time.Duration type. Both of these are not necessary if the `format` tag is explicitly specified. However, we want to isolate their behavior from other behaviors that used to be part of FormatBytesWithLegacySemantics and FormatTimeWithLegacySemantics. ParseBytesWithLooseRFC4648 and ParseTimeWithLooseRFC3339 are targeted to just historically buggy parsing according to the relevant RFCs, which may need to be enabled by some services for backwards compatibility. While FormatTimeWithLegacySemantics is deleted, we still need FormatBytesWithLegacySemantics to configure highly esoteric aspects of how v1 used to handle byte slices. We rename OmitEmptyWithLegacyDefinition as OmitEmptyWithLegacySemantics to be consistent with other options with the WithLegacySemantics suffix. Updates #71497 Change-Id: Ic660515fb086fe3af237135f195736de99c2bd33 Reviewed-on: https://go-review.googlesource.com/c/go/+/685395 Auto-Submit: Joseph Tsai <joetsai@digital-static.net> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
2025-07-14encoding/json/v2: add security section to docJoe Tsai
This follows up CL 684315 with an expanded section in the v2 doc. Updates #14750 Updates #71845 Change-Id: I1ffa97e030f5f2b709e8142028e3c8e0e38b80ce Reviewed-on: https://go-review.googlesource.com/c/go/+/685195 Auto-Submit: Joseph Tsai <joetsai@digital-static.net> Reviewed-by: Damien Neil <dneil@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
2025-07-11encoding/json/v2: report wrapped io.ErrUnexpectedEOFJoe Tsai
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>
2025-06-30encoding/json/v2: avoid escaping jsonopts.StructJoe Tsai
The jsonopts.Struct.join method unfortunately escapes the receiver because it is passed to JoinUnknownOption, which is a dynamically implemented function. This affects jsontext.Encoder.reset and jsontext.Decoder.reset, which relied on a local jsonopts.Struct to temporarily store prior options such that it would have to be heap allocated. Adjust the signature of JoinUnknownOption to avoid pointers so that nothing escape. This is a regression from https://github.com/go-json-experiment/json/pull/163 Performance: name old time/op new time/op delta Marshal/Bool-32 72.1ns ± 2% 51.3ns ± 1% -28.77% (p=0.000 n=10+9) name old allocs/op new allocs/op delta Marshal/Bool-32 2.00 ± 0% 1.00 ± 0% -50.00% (p=0.000 n=10+10) Updates #71845 Change-Id: Ife500d82d3d2beb13652553a4ffdf882c136f5a0 Reviewed-on: https://go-review.googlesource.com/c/go/+/685135 Auto-Submit: Joseph Tsai <joetsai@digital-static.net> Reviewed-by: Damien Neil <dneil@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
2025-06-25encoding/json/jsontext: rename Encoder.UnusedBuffer as Encoder.AvailableBufferJoe Tsai
This follows the precedent set by: bufio.Writer.AvailableBuffer bytes.Buffer.AvailableBuffer both with methods that return a zero-length buffer that is intended to only be used with a following Write call. This keeps the older UnusedBuffer method around so that at least one commit that has both methods for migration purposes. Updates #71497 Change-Id: I3815f593e09f645280ae5ad9cbdd63a6c147123b Reviewed-on: https://go-review.googlesource.com/c/go/+/683896 Reviewed-by: Damien Neil <dneil@google.com> TryBot-Bypass: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
2025-06-24encoding/json/v2: support ISO 8601 durationsJoe Tsai
Based on the discussion in #71631, it is hotly contested whether the default JSON representation for a Go time.Duration should be the time.Duration.String format or a particular profile of ISO 8601. Regardless of the default, it seems clear that we should at least support ISO 8601 if specified via a format flag. Note that this CL does not alter the default representation. Unfortunately, ISO 8601 is a large and evolving standard with many optional extensions and optional restrictions. Thus, the term "ISO 8601 duration" unfortunately does not resolve to a particular grammar, nor one that is stable. However, there is precedence that we can follow in this matter. JSON finds its heritage in JavaScript and JavaScript is adding a Temporal.Duration type whose default JSON representation is ISO 8601. There is a well-specified grammar for their particular profile of ISO 8601, which is documented at: https://tc39.es/proposal-temporal/#prod-Duration This particular CL adds support for ISO 8601 according to the exact same grammar that JavaScript uses. While Temporal.Duration is technically still a proposal, it is already in stage 3 of the TC39 proposal process (i.e., "no changes to the proposal are expected" and "has been recommended for implementation") and therefore close to final adoption. One major concern with ISO 8601 is that it supports nominal date units like years, months, weeks, and days that do not have an accurate meaning without being anchored to a particular point in time and place on Earth. Fortunately, JavaScript (by default) avoids producing Temporal.Duration values with nominal units unless arithmetic in JavaScript explicitly sets a largestUnits value that is larger than "hours". In the Go implementation, we support syntactically parsing the full ISO 8601 grammar (according to JavaScript), but semantically report an error if nominal units are present. This ensures that ISO 8601 durations remain accurate so long as they only use the accurate units of hours, minutes, or seconds. Updates #71631 Change-Id: I983593662f2150461ebc486a5acfeb72f0286939 Reviewed-on: https://go-review.googlesource.com/c/go/+/682403 Reviewed-by: Daniel Martí <mvdan@mvdan.cc> Reviewed-by: Damien Neil <dneil@google.com> Auto-Submit: Joseph Tsai <joetsai@digital-static.net> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
2025-06-24encoding/json/v2: reject unquoted dash as a JSON field nameJoe Tsai
In this blog: https://blog.trailofbits.com/2025/06/17/unexpected-security-footguns-in-gos-parsers/ the concern was raised that whenever "-" is combined with other options, the "-" is intepreted as as a name, rather than an ignored field, which may go contrary to user expectation. Static analysis demonstrates that there are ~2k instances of `json:"-,omitempty" in the wild, where almost all of them intended for the field to be ignored. To prevent this footgun, reject any tags that has "-," as a prefix and warn the user to choose one of the reasonable alternatives. The documentation of json/v2 already suggests `json:"'-'"` as the recommended way to explicitly specify dash as the name. See Example_fieldNames for example usages of the single-quoted literal. Update the v1 json documentation to suggest the same thing. Updates #71497 Change-Id: I7687b6eecdf82a5d894d057c78a4a90af4f5a6e4 Reviewed-on: https://go-review.googlesource.com/c/go/+/683175 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com> Reviewed-by: Damien Neil <dneil@google.com> Auto-Submit: Joseph Tsai <joetsai@digital-static.net> Reviewed-by: Daniel Martí <mvdan@mvdan.cc> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
2025-06-23encoding/json/v2: report error on time.Duration without explicit formatJoe Tsai
The default representation of a time.Duration is still undecided. In order to keep the future open, report an error on a time.Duration without an explicit format flag provided. Updates #71631 Change-Id: I08248404ff6551723851417c8188a13f53c61937 Reviewed-on: https://go-review.googlesource.com/c/go/+/682455 Auto-Submit: Joseph Tsai <joetsai@digital-static.net> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Damien Neil <dneil@google.com>
2025-06-11encoding/json/jsontext, encoding/json/v2: document experimental natureDamien Neil
Change-Id: I7b2c391749e0113e006f37b2ac1ebfe3ee0a4e0e Reviewed-on: https://go-review.googlesource.com/c/go/+/680715 TryBot-Bypass: Damien Neil <dneil@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Joseph Tsai <joetsai@digital-static.net> Auto-Submit: Damien Neil <dneil@google.com>
2025-04-18encoding/json: add json/v2 with GOEXPERIMENT=jsonv2 guardDamien Neil
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>