Support for Automatically Parsing Negative Number Arguments

[thomask77]

I would like to re-open the discussion from issue #555 and #1624.

My program makes heavy use of numeric arguments, including negative numbers, special float values (NaN, Infinity..), negative hex numbers, etc.

At the moment I'm using the following monkey patch as a work-around:

from click.parser import OptionParser, ParsingState


def _is_number(arg: str) -> bool:
    try:
        _ = int(arg, 0)
    except ValueError:
        try:
            _ = float(arg)
        except ValueError:
            return False
    return True


# Allow negative numbers as arguments
#
# Based on click/parser.py v8.1.7
#
def _process_args_for_options(self, state: ParsingState) -> None:
    while state.rargs:
        arg = state.rargs.pop(0)
        if arg == "--":
            return
        elif arg[:1] in self._opt_prefixes and len(arg) > 1 and not _is_number(arg):
            self._process_opts(arg, state)
        elif self.allow_interspersed_args:
            state.largs.append(arg)
        else:
            state.rargs.insert(0, arg)
            return


# Monkey-patch the OptionParser class
#
OptionParser._process_args_for_options = _process_args_for_options

It would be nice, if click would offer an official mode that accepts negative numbers.
I can also submit a PR, but would need further input on how to properly integrate the feature.

[Rowlando13]

Based on looking at the previous issues, the issue results from an argument(-1 or --1) looking like options, and so get parsed that way. In the documentation there are clear work arounds such as pass -- or passing an ignore_unknown_options to the context settings. I am not sure that its worth the parsing complexity. Possibly for integers and floats. @AndreasBackx Thoughts?

https://click.palletsprojects.com/en/stable/arguments/#option-like-arguments

[thomask77]

We are using click in a power-electronics control application, and it's absolutely critical.

There's just no way, we can explain to our customers that they have to use "--" when they want to output a negative voltage.

The additional complexity is minimal, as shown by the monkey patch above.

[AndreasBackx]

I think it's something that should be possible indeed. Though I'm unsure if the proposed solution is ideal. Clap has solved this in a different way which also allows for non-number values that start with dashes: clap-rs/clap#1245. We could possibly explore a similar solution.

I think for now it's good there's a workaround for those who need it. @davidism, would the parser rewrite of yours possible be able to accommodate this more easily?

I think we should think about this in this a bit more in the future. Right now we should catch up with the other issues and PRs that aren't parser related. Then we can tackle the parser related issues possibly in the next major version with the rewrite, or in a further down the line minor release.