cmd/go: go clean -cache silently ignores GOCACHE relative path

[mneverov]

Go version

go version go1.23.1 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/mneverov/.cache/go-build'
GOENV='/home/mneverov/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/mneverov/go/pkg/mod'
GOOS='linux'
GOPATH='/home/mneverov/go'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR='/home/mneverov/tmp'
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.1'
GODEBUG=''
GOTELEMETRY='on'
GOTELEMETRYDIR='/home/mneverov/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/mneverov/go/src/github.com/mneverov/ingress-nginx/go.mod'
GOWORK='/home/mneverov/go/src/github.com/mneverov/ingress-nginx/go.work'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/home/mneverov/tmp/go-build82578650=/tmp/go-build -gno-record-gcc-switches'

What did you do?

GOCACHE='.cache' go clean --cache

What did you see happen?

No output. Neither default gocache directory nor ".cache" directory cleaned up.

What did you expect to see?

Error or empty .cache directory.

[gabyhelp]

Related Issues and Documentation

• cmd/go: clean -n -cache should only print cache removal commands, not run them #27469 (closed)
• cmd/go: clean -cache -n should not delete cache #39250 (closed)
• cmd/go: go clean -testcache fails if GOCACHE directory does not exist #29100 (closed)
• cmd/go: go clean should not accept flags like -modcache with packages #53725 (closed)
• cmd/go clean -testcache does not clean test cache #29757 (closed)
• cmd/go: cache is not aware of go build -trimpath flag #31896 (closed)
• cmd/go: making the output of the `go clean -h` command more informative #68242 (closed)
• "go clean -modcache" shouldn't need to "find" anything #30480 (closed)
• cmd/go: error if GOCACHE is set but is not an absolute path #30447 (closed)
• cmd/go: go clean -modcache should not download modules #36798 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[mneverov]

I see a couple of issues here:

• Documentation https://pkg.go.dev/cmd/go#hdr-Build_and_test_caching does not mention that GOCACHE must be an absolute path.
• No way to check if DefaultDir produces an error.

I'd like to work on this. I see a couple of ways to address the second point.

DefaultDir should return string, bool, error

Pros

1. Consistent with go convention if a function during execution encounters an error it should return the error
2. Function with this signature already exists: cfg.EnvFile

Cons

1. Looks ugly to me
2. Change should be propagated to 8 places that uses the function

Introduce func DefaultDirError() error { return defaultDirErr }

Pros

1. Can be used only where needed (go clean command) to check the error

Cons

1. Implicit dependency: should be used only after DefaultDir is called. Can be fixed with the proper comment.
2. Introduces new public method.

[cagedmantis]

cc @matloob @samthanawalla

[matloob]

I don't think we need to document the absolute path requirement in the "Build and test caching" section, but that we should in the GOCACHE entry in the https://pkg.go.dev/cmd/go#hdr-Environment_variables section.

I agree that there's no nice way to address the second point, though my preference is to return string, bool, error. (We already had to change the usages to ignore the ok value when we added it and this is a similar addition)

[gopherbot]

Change https://go.dev/cl/628596 mentions this issue: cmd/go: fail go clean command when failed to find go cache directory