Avoid C414 for stable multi-key sorted calls

CHANGELOG.rst

@@ -5,6 +5,12 @@ Changelog
 Unreleased
 ----------
 
+* Fix a C414 false positive for nested ``sorted()`` calls where the outer call
+  specifies a non-``None`` ``key``, including potentially through a ``**``
+  expansion.
+
+  Fixes `Issue #661 <https://github.com/adamchainz/flake8-comprehensions/issues/661>`__.
+
 * Support Python 3.15.
 
 * Switch package build backend from setuptools to `uv_build <https://docs.astral.sh/uv/concepts/build-backend/>`__.

README.rst

@@ -158,6 +158,7 @@ C414: Unnecessary ``<list/reversed/set/sorted/tuple>`` call within ``<list/set/s
 --------------------------------------------------------------------------------------------------
 
 It's unnecessary to double-cast or double-process iterables by wrapping the listed functions within ``list``/``set``/``sorted``/``tuple``.
+One exception is a nested ``sorted()`` call where the outer call has a non-``None`` ``key``, including potentially through a ``**`` expansion, since the stable sorts can establish primary and secondary orderings.
 For example:
 
 * Rewrite ``list(list(iterable))`` as ``list(iterable)``

src/flake8_comprehensions/__init__.py

@@ -239,6 +239,21 @@ def run(self) -> Generator[tuple[int, int, str, type[Any]]]:
                             node.func.id in {"set", "sorted"}
                             and node.args[0].func.id
                             in {"list", "reversed", "sorted", "tuple"}
+                            and not (
+                                node.func.id == "sorted"
+                                and node.args[0].func.id == "sorted"
+                                and (
+                                    has_double_star_args(node)
+                                    or any(
+                                        keyword.arg == "key"
+                                        and not (
+                                            isinstance(keyword.value, ast.Constant)
+                                            and keyword.value.value is None
+                                        )
+                                        for keyword in node.keywords
+                                    )
+                                )
+                            )
                         )
                         or (
                             node.func.id in {"list", "tuple"}

tests/test_flake8_comprehensions.py

@@ -610,6 +610,9 @@ def test_C413_fail(code, failures, flake8_path):
         "list(set(a))",
         "tuple(set(a))",
         "sorted(set(a))",
+        "sorted(sorted(a), key=len)",
+        "sorted(sorted(a), **kwargs)",
+        'sorted(sorted(a), **{"key": len})',
     ],
 )
 def test_C414_pass(code, flake8_path):
@@ -674,6 +677,10 @@ def test_C414_pass(code, flake8_path):
             "sorted(sorted(a), reverse=True)",
             ["./example.py:1:1: C414 Unnecessary sorted call within sorted()."],
         ),
+        (
+            "sorted(sorted(a), key=None)",
+            ["./example.py:1:1: C414 Unnecessary sorted call within sorted()."],
+        ),
         (
             "sorted(sorted(a, reverse=True))",
             ["./example.py:1:1: C414 Unnecessary sorted call within sorted()."],