Fix false positive for unnecessary-lambda. (#9149) (#9200)

This simplifies the check for the call having kwargs but not the lambda.

(cherry picked from commit 2289c71)

Co-authored-by: Clément Schreiner <[email protected]>

doc/whatsnew/fragments/9148.false_positive

@@ -0,0 +1,3 @@
+Fixed false positive for ``unnecessary-lambda`` when the call has keyword arguments but not the lambda.
+
+Closes #9148

pylint/checkers/base/basic_checker.py

@@ -519,7 +519,6 @@ def _has_variadic_argument(
         )
 
     @utils.only_required_for_messages("unnecessary-lambda")
-    # pylint: disable-next=too-many-return-statements
     def visit_lambda(self, node: nodes.Lambda) -> None:
         """Check whether the lambda is suspicious."""
         # if the body of the lambda is a call expression with the same
@@ -544,29 +543,20 @@ def visit_lambda(self, node: nodes.Lambda) -> None:
             # return something else (but we don't check that, yet).
             return
 
-        call_site = astroid.arguments.CallSite.from_call(call)
         ordinary_args = list(node.args.args)
         new_call_args = list(self._filter_vararg(node, call.args))
         if node.args.kwarg:
-            if self._has_variadic_argument(call.kwargs, node.args.kwarg):
+            if self._has_variadic_argument(call.keywords, node.args.kwarg):
                 return
+        elif call.keywords:
+            return
 
         if node.args.vararg:
             if self._has_variadic_argument(call.starargs, node.args.vararg):
                 return
         elif call.starargs:
             return
 
-        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
-
         # The "ordinary" arguments must be in a correspondence such that:
         # ordinary_args[i].name == call.args[i].name.
         if len(ordinary_args) != len(new_call_args):

tests/functional/u/unnecessary/unnecessary_lambda.py

@@ -52,6 +52,10 @@
 _ = lambda: _ANYARGS(*[3], **{'three': 3})
 _ = lambda: _ANYARGS(func=42)
 
+# pylint: disable=missing-function-docstring
+def f(d):
+    print(lambda x: str(x, **d))
+
 # Don't warn about this.
 _ = lambda: code().analysis()