Improve the `filename` argument of `pdb`'s `break` command

[gaogaotiantian]

Feature or enhancement

Proposal:

Currently in the docs we say b(reak) command can take a filename, but we are very vague about it. It only mentioned the file will be searched in sys.path.

The actual implementation currently allows:

• absolute path
• relative path (including a path with /, so not only "filename")
• module name (only if module.py is in sys.path)

As you can tell, we allow module name like pprint:100, but not package.module like multiprocessing.queue:100, however, multiprocessing/queue.py:100 works. This is inconsistent by itself, let alone the lack of description.

I'm making a PR to clean this up a bit. This PR will improve the lookupmodule function to support package.module, and clean up both code and docs.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-117618: Make package.module searchable for breakpoints and clean up docs #117619