[feature request] New warning: too many positional arguments

[sabik]

Current problem

With R0913 too-many-arguments now including keyword arguments (#8667), the reasonable setting for max-args is now larger, since it's not really a problem to have a dozen keyword-only arguments.

However, having a dozen positional arguments remains a poor design.

Desired solution

A new warning for too many positional arguments, with a separately configurable maximum. This would warn when there are more than a very small number of positional arguments (including positional-only arguments).

This would be in addition to the existing too-many-arguments warning.

Additional context

This has been previously suggested in comments on #8667

[jacobtylerwalls]

+1

[mbyrnepr2]

As for specification would this proposed checker be for emitting a message where a function or class is called? (as opposed to too-many-arguments which is emitted for the function or class definition. It sounds similar to the existing #385.

[jacobtylerwalls]

As I'm hearing the request, it's just on the definition (and that's what I would suggest, too).

[sabik]

Yeah, I intended this to be on the definition, just like the too-many-arguments warning (but excluding keyword-only arguments from the count and with a separate maximum)

[mbyrnepr2]

I think the idea behind too-many-arguments is that, regardless of the argument being positional or keyword or positional-only (etc.), the function is complex by having too many of them (subjective I know :D) and doing too many things. At definition time this is possible because we have all the information we need (the number of params).

Would the new checker raise for this situation (where the function call has explicitly passed the names of the parameters)?

def tomato(one, two, three, four, five, six):
    ...

tomato(one=1, two=2, three=3, four=4, five=5, six=6)

Perhaps if it were to raise for positional-only, then raising at definition time is ok:

def tomato(one, two, three, four, five, six, /):
    ...

tomato(1, 2, 3, 4, 5, 6)

[sabik]

Yeah; the idea was that the new checker would raise for:

def tomato(one, two, three, four, five, six):
    ...

and also raise for:

def tomato(one, two, three, four, five, six, /):
    ...

It would be OK with

def tomato(one, two, *, three, four, five, six):
    ...

and OK with

def tomato(*, one, two, three, four, five, six):
    ...

In any case, I was thinking of definition time; the design of the function encourages calls with a confusing undifferentiated argument list, regardless of whether or not it's called that way (or called at all).

Call time would be more of a variant of #385, function actually being called with a confusing undifferentiated argument list, which is not what I was thinking of here...