UX: error on 'directory does not exist'

[lczyk]

The error message when attempting to cut into a directory (to make sure all the slice is correct) is a bit confusing. When running: chisel cut --release=./ --root=mych libgcc-14-dev_libs i get error: cannot extract from package "base-files": target directory does not exist which gives me the full error hierarchy and points towards something wrong with the base-files, while the actual issue is that the directory mych does not exist.

As a UX feedback; I'd suggest caching this case and creating a more user friendly error. At least I'd present just the bottom error, and maybe even add the directory name. Something like cannot cut into mych directory. it does not exist.

I imagine this kind of treatment might be appropriate for some other errors, therefore my suggestion for reporting errors to the user would be to:

• allow the error to propagate to the topmost level normally - exactly as it is implemented at the moment
• just before passing the error to the user, check whether it is a special error which can be made more user friendly.
  • Yes: report it like that
  • No: Report it using the

I'm thinking of something along the lines of github.com/pkg/errors used to do?

When I have some time I'm happy to look at the code and make a PR.

[lczyk]

related to #206

[letFunny]

I think the proposed UX is better than what we have, thank you for that! I think there is a much simpler way to accomplish it than creating custom errors and wrapping, unwrapping. That is, we can check for the existence of the target directory in slicer and return a more appropriate error given the different context. Note that this doesn't mean we should remove the check in extract.go as it is a separate subsystem with its own API and requirements.

For example, in slicer.go we could:

	_, err = os.Stat(options.TargetDir)
	if os.IsNotExist(err) {
		return fmt.Errorf("target directory does not exist")
	} else if err != nil {
		return err
	}