cmd/go: Since 1.18.1, go run always uses -buildvcs=false

[mgabeler-lee-6rs]

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

$ go version
go version go1.18.1 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/circleci/.cache/go-build"
GOENV="/home/circleci/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/circleci/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/circleci/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.1"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="0"
GOMOD="/home/circleci/project/go.mod"
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2409035375=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Attempting to extract VCS info from debug.ReadBuildInfo() when running under go run.

1. https://go.dev/play/p/_09ZOz1UlC7
2. Create a new directory
3. go mod init example
4. Save the playground code as main.go
5. git add . && git commit -m 'example'
6. go run .

What did you expect to see?

With go 1.18.0, I get:

$ go run . 
-compiler gc
CGO_ENABLED 1
CGO_CFLAGS 
CGO_CPPFLAGS 
CGO_CXXFLAGS 
CGO_LDFLAGS 
GOARCH amd64
GOOS linux
GOAMD64 v1
vcs git
vcs.revision 3905f8828680bce9d913660e098c704687ec309b
vcs.time 2022-04-13T20:07:46Z
vcs.modified false

What did you see instead?

With go 1.18.1:

$ go run . 
-compiler gc
CGO_ENABLED 0
GOARCH amd64
GOOS linux
GOAMD64 v1

Even worse, -buildvcs=auto is not recognized:

$ go run -buildvcs=auto .
invalid boolean value "auto" for -buildvcs: parse error
usage: go run [build flags] [-exec xprog] package [arguments...]
Run 'go help run' for details.

Even even worse, -buildvcs=true is ignored:

$ go run -buildvcs=true .
-compiler gc
CGO_ENABLED 0
GOARCH amd64
GOOS linux
GOAMD64 v1

[mgabeler-lee-6rs]

Presumably this is (unintentional) fallout from #51723 and/or #51748

[seankhliao]

The backport for -buildvcs=auto is still open, so that's not expected to work yet #51798

cc @bcmills @matloob

[bcmills]

go run intentionally should not stamp VCS metadata. It has a nonzero latency cost and essentially zero benefit; the fact that it happened to stamp the binary in Go 1.18 was a bug missed during pre-release testing.

go run may be used with or without an explicit version.

• With an explicit version, there is no applicable VCS containing the package anyway.
• Without an explicit version, the VCS metadata can be recovered by running the VCS tool manually, since (by definition) go run does not result in a binary to be stored and shipped separately from the VCS and the go run command must have occurred within the repository.

[mgabeler-lee-6rs]

@bcmills I ask you reconsider for the following context/reasons:

1. The use case of go run . has VCS data available
2. At the very least, if go run is never going to stamp VCS data, then it should report an error if you invoke it as go run -buildvcs=true. Currently it accepts this flag but silently ignores it.