time: output does not respect comma as millisecond separator

[746B61]

What version of Go are you using (go version)?

$ go version
go version go1.17 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/xxx/.cache/go-build"
GOENV="/home/xxx/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/xxx/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/xxx/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.17"
GCCGO="gccgo"
AR="ar"
CC="x86_64-pc-linux-gnu-gcc"
CXX="x86_64-pc-linux-gnu-g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1250957969=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I used time.Format to format a time including milliseconds with layout string "15:04:05,000". Before go 1.17, the comma was not recognized as separator for milliseconds and the string ,000 was added to the format output verbatim. The result was for example 23:00:12,000. Since go 1.17, the comma is recognized as separator for milliseconds, but changed to a period in the output. The result now is for example 23:00:12.345. I expect the result respect the comma in the layout string and getting 23:00:12,345.

Having the zeros replaced with the actual milliseconds changed the behavior to previous versions but is an improvement from my perspective. But, the changed behavior regarding the comma as separator breaks existing code that relies on a comma being used, e.g., because it is parsed by some other system later on.

Example code: https://play.golang.org/p/Bq6p4dxqhgG

What did you expect to see?

23:00:12,345
(or 23:00:12,000 as in go <1.17)

What did you see instead?

23:00:12.345

[WangLeonard]

Its behavior is changed by this commit f02a26b

[gopherbot]

Change https://golang.org/cl/345438 mentions this issue: time/format: support comma as separator for fractional seconds

[cherrymui]

cc @rsc @robpike

[AlekSi]

Please consider backporting it into 1.17.

[cherrymui]

@gopherbot please consider backporting it into 1.17. Thanks.

[gopherbot]

Backport issue(s) opened: #48177 (for 1.17).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.

[gopherbot]

Change https://golang.org/cl/350149 mentions this issue: [release-branch.go1.17] time: propagate "," separator for fractional seconds into Format