gh-117941: Reject option names starting with "--no-" in argparse.BooleanOptionalAction

[serhiy-storchaka]

They never worked correctly.

• Issue: BooleanOptionalAction does not correctly resolve arguments that are defined as starting with "--no-" #117941

[savannahostrowski]

LGTM, but I think we should also update the documentation to reflect that --no-foo is no longer supported, right? The blurb from the docs:

You may also specify an arbitrary action by passing an Action subclass or other object that implements the same interface. The BooleanOptionalAction is available in argparse and adds support for boolean actions such as --foo and --no-foo:

[serhiy-storchaka]

It never was supported. Just now you will get an error instead of wrong result when you use BooleanOptionalAction in the way it was not supposed to be used.

[savannahostrowski]

Right, but isn't the text I mentioned above suggesting that --no-foo can be used with BooleanOptionalAction? After this PR is merged, this is no longer recommended, as you'll get an error, so shouldn't we remove this as an example in the documentation?

[serhiy-storchaka]

but isn't the text I mentioned above suggesting that --no-foo can be used with BooleanOptionalAction?

Read it in the context. The following example shows that it creates action for --no-foo when '--foo' is passed to add_argument().

[savannahostrowski]

Yeah, I see the example. It just sort of reads a bit unclear to me and implies that I should be able to create a parser with:
parser.add_argument('--no-foo', action=argparse.BooleanOptionalAction), which is no longer the case. My comment was more about creating clarity in the docs that --no- prefixed options are not supported.

[serhiy-storchaka]

I do not see anything that implies that '--no-foo' works. And it never worked.

[serhiy-storchaka]

Thank you for your review @savannahostrowski.