Fix pytest.mark.usefixtures() without arguments silently erroring

AUTHORS

@@ -103,6 +103,7 @@ Cornelius Riemenschneider
 CrazyMerlyn
 Cristian Vera
 Cyrus Maden
+Daara Shaw
 Damian Skrzypczak
 Daniel Grana
 Daniel Hahler
@@ -209,6 +210,7 @@ Jeff Rackauckas
 Jeff Widman
 Jenni Rinker
 Jens Tröger
+Jiajun Xu
 John Eddie Ayson
 John Litborn
 John Towler

changelog/12426.improvement.rst

@@ -0,0 +1 @@
+A warning is now issued when :ref:`pytest.mark.usefixtures ref` is used without specifying any fixtures. Previously, empty usefixtures markers were silently ignored.

src/_pytest/fixtures.py

@@ -71,6 +71,7 @@
 from _pytest.scope import HIGH_SCOPES
 from _pytest.scope import Scope
 from _pytest.warning_types import PytestRemovedIn9Warning
+from _pytest.warning_types import PytestWarning
 
 
 if sys.version_info < (3, 11):
@@ -1562,7 +1563,13 @@
 
     def _getusefixturesnames(self, node: nodes.Item) -> Iterator[str]:
         """Return the names of usefixtures fixtures applicable to node."""
-        for mark in node.iter_markers(name="usefixtures"):
+        for marker_node, mark in node.iter_markers_with_node(name="usefixtures"):
+            if not mark.args:
+                marker_node.warn(
+                    PytestWarning(
+                        f"usefixtures() in {node.nodeid} without arguments has no effect"
+                    )
+                )
             yield from mark.args
 
     def getfixtureclosure(

testing/plugins_integration/pytest.ini

@@ -3,4 +3,5 @@ addopts = --strict-markers
 asyncio_mode = strict
 filterwarnings =
     error::pytest.PytestWarning
+    ignore:usefixtures.* without arguments has no effect:pytest.PytestWarning
     ignore:.*.fspath is deprecated and will be replaced by .*.path.*:pytest.PytestDeprecationWarning

testing/python/fixtures.py

@@ -1435,6 +1435,23 @@ def test_two(self):
         reprec = pytester.inline_run()
         reprec.assertoutcome(passed=2)
 
+    def test_empty_usefixtures_marker(self, pytester: Pytester) -> None:
+        """Empty usefixtures() marker issues a warning (#12439)."""
+        pytester.makepyfile(
+            """
+            import pytest
+
+            @pytest.mark.usefixtures()
+            def test_one():
+                assert 1 == 1
+        """
+        )
+        result = pytester.runpytest()
+        result.stdout.fnmatch_lines(
+            "*PytestWarning: usefixtures() in test_empty_usefixtures_marker.py::test_one"
+            " without arguments has no effect"
+        )
+
     def test_usefixtures_ini(self, pytester: Pytester) -> None:
         pytester.makeini(
             """