feat: Annotated based argparse, and auto completer inference

[KelvinChung2000]

This is a full rework of #1612. Instead of wrapping Typer. We now extract the types and build the argparse parser.

I want to mark it as a draft for now, as some of the stuff will likely need a bit more cleanup. Please have a look at the documentation and example, and let me know if I missed anything obvious.

[codecov]

Codecov Report

❌ Patch coverage is 97.08029% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.40%. Comparing base (ca8495e) to head (1834450).

Files with missing lines	Patch %	Lines
cmd2/annotated.py	97.68%	5 Missing ⚠️
cmd2/decorators.py	92.85%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1614      +/-   ##
==========================================
- Coverage   99.51%   99.40%   -0.12%     
==========================================
  Files          21       22       +1     
  Lines        4758     5031     +273     
==========================================
+ Hits         4735     5001     +266     
- Misses         23       30       +7     

Flag	Coverage Δ
unittests	99.40% <97.08%> (-0.12%)	⬇️

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[KelvinChung2000]

I started working on this before I closed that PR. While this PR is still using LLMs, I have a much better understanding of what it is writing, since it is based on Python type processing, which I am much more familiar with than click. As mentioned, this code needs some more cleanup before it's ready for review; that's why this is a draft. However, I would like some feedback on the documentation and the example to make sure I haven't missed anything obvious. If you'd prefer to defer until it is fully ready, that's fine as well.

[tleonhardt]

I'm curious to see where this goes. I can't make any promises in advance, but it sounds like a potentially interesting feature. Though, I would prefer for all the tests to pass before I spend any time reviewing it.

If the code isn't too complex so that it appears to integrate with the rest of cmd2 in a way that is easy to maintain I could see it being a valuable addition.

If for some reason it doesn't immediately integrate well, there may be the possibility of creating a new open-source module that generates argparse argument parsers from type annotations.

[tleonhardt]

Need to fix fundamental type error causing all tests and mypy to fail:

cmd2/annotated.py:234:5: error: "Callable[[str], Enum]" has no attribute "_cmd2_enum_class"  [attr-defined]

[KelvinChung2000]

I am aware of this. I am working on the code's style right now. I will push once it is at a good enough state.

This page of code contains all the logic required to generate the argparser. While it is not too difficult to understand, I don't like the long if-else chain because it is not intuitive.

[tleonhardt]

I haven't look at this particular case, but since cmd2 now only supports Python 3.10 or newer, using the match statement can be a nice option for structural pattern matching with match/case to replace some long if/else chains.

[KelvinChung2000]

I originally considered something like a dict dispatch pattern:

def dis(type_to_resolve):
    type_dict = {Enum: _reslove_enum}
    return type_dict[type_to_resolve]

But the things that return for the _resolve_* are too different, and are slowly moving toward more like filling in an "argparse specification," then having a function that takes in this specification and turns it into a parser.

I like this dict dispatch pattern because it is very easy to read and extend, but it might not be the right pattern here.