cmd/go: fmt suggests -buildvcs when it doesn't take build flags

[ocket8888]

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

$ go version
go version 1.18 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/ocket8888/.cache/go-build"
GOENV="/home/ocket8888/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/ocket8888/pkg/mod"
GONONPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/ocket8888"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="REDACTED"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="REDACTED"
GOVCS="*:off"
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
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-build1502895740=/tmp/go-build -gno-record-gcc-switches"

What did you do?

mkdir -p "$GOPATH/src/example.com/m"
cd "$GOPATH/src/example.com/m"
go mod init
cat > main.go <<-EOF
package main
import "fmt"

func main(){
fmt.Println("Hello World!");
}
EOF
mkdir .git
go fmt ./...

What did you expect to see?

package main

import "fmt"

func main() {
    fmt.Println("Hello World!")
}

What did you see instead?

go: missing Git command. See https://golang.org/s/gogetcmd
error obtaining VCS status: exec: "git": executable file not found in $PATH
        Use -buildvcs=false to disable VCS stamping.

Note that this error message is incorrect as neither go nor go fmt accept the -buildvcs flag. Also note that GOVCS is set to *:off.

[mvdan]

This will be solved by #51748 in Go 1.18.2, but I agree that it's unexpected that go fmt would do any VCS build stamping at all. It shouldn't be doing any building.

[ocket8888]

Will the fix be backported? Ultimately that doesn't actually matter to me unless backporting would happen sooner than the 18.2 release. Otherwise I'd just upgrade. But still curious.

[seankhliao]

Given that 1.18.1 is out, 1.18.2 is the soonest release it can be in. Backport issue is #51798

[ocket8888]

Well that's about changing build behavior, right? With go fmt I can't explicitly enable or disable vcs stamping - because it shouldn't need to do that at all, no? gofmt itself doesn't do anything like that, just seems like a true bug in the invocation. Because if it does find git then according to the proposal for --buildvcs=auto in #51798, the go fmt run will fail if invocation of git fails for some reason. But go fmt shouldn't depend on git at all, because gofmt doesn't.

[mvdan]

Right, this seems like a regression bug. I imagine 1.18.2 will be out sometime over the next week; it's already been four weeks since 1.18 and usually there would have been a bugfix release two weeks ago.

I think keeping this issue open is worthwhile because it's not a dupliate; as already stated, there's presumably no reason for go fmt to stamp VCS information.

[seankhliao]

I believe it may have been unintentionally fixed in 1.18.1 already by #51723, which restricts when buildvcs is included (eg go run doesn't have it now, #52338).
strace -f go fmt 2>&1 | grep execve doesn't show git being called for 1.18.1, but it does for 1.18

[mvdan]

Ah, you're right. 1.18.1 was announced as a security release, so I assumed it only contained security fixes, but it doesn't.

[ocket8888]

I didn't check 1.18.1 - didn't realize that existed when I wrote the example. I'll check that out and close the issue if it's resolved in the newest release. (or should I leave it open for tracking backport?)

[ocket8888]

1.18.1 doesn't have this problem