Allow loading extensions via relative paths

[chrisbouchard]

The Problem

I would like to use relative import paths to describe my extensions, e.g., .extensions.foo rather than requiring an absolute path like my_bot.extensions.foo. I use relative paths for package-internal imports, so it seems logical that extensions would follow the same pattern.

This does not currently work. I get the following error:

Traceback (most recent call last):
  File "/usr/lib64/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib64/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/chris/Projects/discord-fate-bot/discord_fate_bot/__main__.py", line 15, in <module>
    bot.load_extension('.extensions.error_handling')
  File "/home/chris/.local/share/virtualenvs/discord-fate-bot-MUSnTVTS/lib/python3.7/site-packages/discord/ext/commands/bot.py", line 621, in load_extension
    lib = importlib.import_module(name)
  File "/home/chris/.local/share/virtualenvs/discord-fate-bot-MUSnTVTS/lib64/python3.7/importlib/__init__.py", line 122, in import_module
    raise TypeError(msg.format(name))
TypeError: the 'package' argument is required to perform a relative import for '.extensions.error_handling'

It would seam this library is using importlib internally, which can handle relative paths, but is not passing enough parameters.

The Ideal Solution

I would like Bot.load_extension to take an optional second parameter, which would specify the package to resolve against. This follows the example of importlib.import_module, which takes a package parameter in the same way. If no package is provided, the path is looked up as if from a top-level script (the current behavior).

This would allow us to say

bot.load_extension('.extensions.foo', __package__)

which would load the extension relative to the current package.

The Current Solution

Currently the solution is to only use absolute paths. I use importlib.utils.resolve_name to resolve my relative paths to absolute ones:

from importlib.util import resolve_name
# ...
bot.load_extension(resolve_name('.extensions.foo', __package__))

Summary

Please allow us to load extensions using relative paths via an optional package parameter in Bot.load_extension.

This feature request looks similar to #1703, but that request wants something similar old Python 2.x-style relative paths (just concatenating package and name with a dot). I would like something compatible with Python 3 and importlib.

I would be willing to work on a merge request. I just wanted to make an issue first in case there was a conscious decision not to support relative paths. (I would still ask you to reconsider.)