False positive: unnecessary lambda with kwargs in the call

[clemux]

Bug description

# pylint: disable=missing-module-docstring,undefined-variable,missing-function-docstring
def f(a, d):
    print(lambda x: a(x, **d))   

Configuration

No response

Command used

pylint test.py

Pylint output

************* Module test
test.py:3:2: W0108: Lambda may not be necessary (unnecessary-lambda)

------------------------------------------------------------------
Your code has been rated at 0.00/10 (previous run: 0.00/10, +0.00)

Expected behavior

---

Your code has been rated at 10.00/10 (previous run: 0.00/10, +10.00)

Pylint version

pylint 3.0.1
astroid 3.0.0
Python 3.11.4 (main, Jun  9 2023, 07:59:55) [GCC 12.3.0]

OS / Environment

Distributor ID: Ubuntu
Description: Ubuntu 23.04
Release: 23.04
Codename: lunar

Additional dependencies

No response

[clemux]

I stumbled upon this false positive for W0108 (unnecessary-lambda) in the tests of pandas, for example this

I've looked into the implementation, and this part looks weird to me:

        if call.keywords:
            # Look for additional keyword arguments that are not part
            # of the lambda's signature
            lambda_kwargs = {keyword.name for keyword in node.args.defaults}
            if len(lambda_kwargs) != len(call_site.keyword_arguments):
                # Different lengths, so probably not identical
                return
            if set(call_site.keyword_arguments).difference(lambda_kwargs):
                return

As far as I can tell, lambda_kwargs is always empty because of this condition at the beginning of the check

        if node.args.defaults:
            return

In the case of my example, len(call_site.keyword_arguments) is empty. I don't know why it is empty, or even why the condition is made on this instead of simply comparing call.keywords and node.args.kwargs, but it explains why the warning is triggered here.