support exit code for custom commands

[garethr]

I was experimenting with adding a set of validation commands to my cue configuration, in _tools.cue files. The commands they exec out to will return non-zero exit codes when those commands fail, but running them via the cue <cmd> runner eats those exit codes and always returns 0. Checking the code this doesn't appear to be something I can add to the print task.

cue/cmd/cue/cmd/custom.go

Lines 299 to 310 in 2b0e7cd

	func (c *printCmd) Run(ctx context.Context, v cue.Value) (res interface{}, err error) {
	str, err := v.Lookup("text").String()
	if err != nil {
	return nil, err
	}
	if testOut != nil {
	fmt.Fprintln(testOut, str)
	} else {
	fmt.Println(str)
	}
	return nil, nil
	}

Is there a way of achieving this at present? Supporting passing through the exit codes would make integration of cue commands into pipelines easier.

[mpvl]

Yes, it makes sense to at least return a non-zero error code on failure. To what extent does it need to be the same code? As there may be multiple tasks executed concurrently, returning the code of the failed first task may result in indeterministic behavior, so simply returning 1, for instance, may be a better approach.

[garethr]

Agreed, returning 1 makes sense in all the cases I have in mind.

[garethr]

Thanks, just tested this out and this works for me. Appreciated.

[cueckoo]

This issue has been migrated to cue-lang/cue#30.

For more details about CUE's migration to a new home, please see cue-lang/cue#1078.