better failure when ~/.docker/config.json has a busted credential helper

[vito]

Displayed error message

resolve failed: error getting credentials - err: exec: "docker-credential-desktop": executable file not found in $PATH, out: ``

To Reproduce

With a bad credStore in ~/.docker/config.json, run any kind of thunk:

(run (from (linux/alpine) ($ echo "Hello")))

I'm not really sure what makes credStore become "bad" but it's a thing that can happen. Would appreciate if someone could post an example bad configuration here!

I ran into a similar error on OS X when I didn't have docker-credential-osxkeychain installed.

I suspect this is sometimes the result of bit-rotten ~/.docker/config.json from not having used Docker in a while on the machine, but letting it auto-update. Just a wild guess though. Seems like Docker is OK with the config while Bass is not.

Suggested message
What would have helped you identify the root cause quicker?

It would be great to point the user towards ~/.docker/config.json to try to clean it up, or try running a Docker command to confirm that it's broken.

[srenatus]

Regarding "bad", that's the config I had, never having touched it myself before:

{"auths":{"ghcr.io":{},"https://index.docker.io/v1/":{}},"credsStore":"desktop","currentContext":"default","experimental":"enabled","stackOrchestrator":"swarm"}

I had changed the key to _credsStore, assuming that that would disable it, and it seemed to work fine after that change.

[srenatus]

FWIW that executable seems to be in my PATH

$ which docker-credential-desktop                     
/usr/local/bin/docker-credential-desktop

[vito]

Great, thanks.

One thing that's probably happening here is it's choking on Bass's sanitization of the process env:

bass/pkg/bass/env.go

Lines 10 to 21 in b63ace4

	func ImportSystemEnv() *Scope {
	env := NewEmptyScope()
	for _, v := range os.Environ() {
	kv := strings.SplitN(v, "=", 2)
	env.Set(Symbol(kv[0]), String(kv[1]))
	}
	os.Clearenv()
	return env
	}

So it might have been properly configured, but by the time the Buildkit runtime tried to use it the $PATH had been cleared. That's definitely a bug.

Might be worth keeping some critical env vars like $PATH around.

[vito]

fixed by #218