GH-139862: Remove color from HelpFormatter

[savannahostrowski]

After digging into this, I think that we should just remove color from being passed into HelpFormatter, since this never worked and was never documented. IMO, this should be controlled by the parser anyway.

• Issue: Investigate argparse formatter handling of color #139862

[hugovk]

(Updated from main to fix the Android failure: #142289)

[hamdanal]

This PR broke instantiating the formatter outside the parser because _theme is no longer set in __init__ as _set_color is no longer called.

import argparse

formatter = argparse.HelpFormatter(prog="program")
formatter.add_usage(usage=None, actions=[], groups=[])
print(formatter.format_help())

This now raises an AttributeError:

Traceback (most recent call last):
  File "/tmp/t.py", line 5, in <module>
    print(formatter.format_help())
          ~~~~~~~~~~~~~~~~~~~~~^^
  File "/tmp/argparse.py", line 303, in format_help
    help = self._root_section.format_help()
  File "/tmp/argparse.py", line 228, in format_help
    item_help = join([func(*args) for func, args in self.items])
                      ~~~~^^^^^^^
  File "/tmp/argparse.py", line 315, in _format_usage
    t = self._theme
        ^^^^^^^^^^^
AttributeError: 'HelpFormatter' object has no attribute '_theme'

This only broke a test over at https://github.com/hamdanal/rich-argparse and I am not sure if it a supported usage of the formatter. Let me know if I need to create an issue/PR.

[savannahostrowski]

Hey @hamdanal, thanks for raising this! Direct instantiation of HelpFormatter should continue to work. I think the fix is to call self._set_color(False) at the end of __init__ to initialize _theme with a no-color default. The parser can still override it afterward. I've put up #142384 to address this.

[hugovk]

@hamdanal And thank you for testing the nightly and reporting so quickly :)