Using golang.org/dl/go1.12 with testscript

[pwaller]

Hi, I have go in my $PATH by symlinking to a golang.org/dl/go* binary. The problem is, that binary seems to locate itself by using the home directory.

The net result is that when I run this, exec go build doesn't work, because:

> exec go build
[stderr]
go1.12: not downloaded. Run 'go1.12 download' to install to /no-home/sdk/go1.12

... i.e, it thinks it isn't yet installed. Any tricks for working around this?

[myitcv]

@mvdan - do you use golang.org/dl/go*?

I'm afraid I don't use it. Instead I have full installs and use process mount namespaces to flip between versions (largely to avoid any issues with binaries being called go1.12 etc)

[mvdan]

Hmm, I do use golang.org/dl/go* for old Go versions. Right now, I have go1.11.5 set up via that.

Perhaps a way to work around this would be to run testscript with an explicit GOROOT, and then teach programs like go1.11.5 to look there.

[mvdan]

With https://go.dev/doc/toolchain existing today, I think this problem is "solved" as long as GOTOOLCHAIN is forwarded into testscripts. We already have a bit of code that does this for other env vars, so we could add it there as well:

go-internal/testscript/testscript.go

Lines 457 to 470 in 2af95f2

	// These env vars affect how a Go program behaves at run-time;
	// If the user or `go test` wrapper set them, we should propagate them
	// so that sub-process commands run via the test binary see them as well.
	for _, name := range []string{
	// If we are collecting coverage profiles, e.g. `go test -coverprofile`.
	"GOCOVERDIR",
	// If the user set GORACE when running a command like `go test -race`,
	// such as GORACE=atexit_sleep_ms=10 to avoid the default 1s sleeps.
	"GORACE",
	} {
	if val := os.Getenv(name); val != "" {
	env.Vars = append(env.Vars, name+"="+val)
	}
	}