cmd/go: GOCACHE=false is not the same as GOCACHE=off

[poy]

Please answer these questions before submitting your issue. Thanks!

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

go version
go version go1.11.1 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/pivotal/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/pivotal/workspace/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/44/zr3txl1n45b23kd2kgx1xqq00000gn/T/go-build585099442=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

GOCACHE=false go test ./...

What did you expect to see?

go's test cache turned off

What did you see instead?

Left the cache on and created a folder named false. I've noticed several devs (including myself) expect type to be a bool instead of a more human readable value.

[ianlancetaylor]

Well, GOCACHE=off is documented. It's a special case. And every new value we treat as disabling the cache is another special case. It seems to me best to minimize special cases, meaning that we should stick to the current documented status.

On the other hand we could perhaps consider failing if GOCACHE is not off and is not an absolute path. It's hard to imagine a use for explicitly setting GOCACHE to anything other than an absolute path.

[poy]

I would agree with the absolute path idea. That would at least surface the misconfiguration without creating an erroneous directory.

[agnivade]

On the other hand we could perhaps consider failing if GOCACHE is not off and is not an absolute path.

I don't see a need to change GOCACHE to allow only absolute paths. Cases like GOCACHE=mycache are not that hard to imagine. There are other environment vars which take relative paths too.

And more importantly, with 1.12 GOCACHE=off is going to go away altogether. https://tip.golang.org/doc/go1.11#gocache. So doing something which is not going to be there anyways seems like wasteful.

[poy]

I didn't realize it was being deprecated. I would agree then.