Empty or incorrect config causes crashes instead of error messages

[frol]

There are all sorts of possible errors with configs, but none are handled at this point.

Legal cases that cause crashes when they shouldn't:

1. Empty invoke.yaml breaks on merge_dict because update data is None.
2. Empty invoke.json raises ValueError in json module itself.

NOTE: When invoke.yaml contains one word (without colon), yaml parser returns a str object, which is also not a dict.

NOTE: Error handling is not implemented in Invoke yet, see #269. So it should get addressed first.

[bitprophet]

Yup, no real smoke testing has been done on that feature yet. Thanks!

[presidento]

I also run into this problem. While not touching other error handling related things, could we recognize empty config files as (valid) empty configs? (May I create a patch for it?)

[bitprophet]

Have a proximate fix for this in now, prompted by #551. A little worried about the root cause though - why is a config level None instead of an empty dict?

#551 is phrased as this being caused by a runtime file (which would imply the issue is with that, relatively new, feature) but the traceback therein seems to show the problem being merging of a user-level file instead, which would mean it's a more generic problem.

---

At a glance it seems to be specifically that PyYAML turns an empty file into None instead of a dict; whether this is on-spec or not doesn't really matter, it's a thing that can happen.

I quickly looked to see what happens with other formats; unfortunately the json module straight up throws a JSONDecodeError if the file is blank instead of eg {}, and there's no nice way to mute that without muting actual "you had JSON and it was bad" or "you accidentally put YAML into a .json" or etc etc, errors.

So, sans a nice clean way to tackle this in a blanket fashion, I am just going to leave my fix as "merge_dicts gracefully handles None input".