Improve rm_rf to handle only known functions

Warnings are emitted if we cannot safely remove
paths.

Fix #5626

testing/test_tmpdir.py

@@ -312,7 +312,20 @@ class TestNumberedDir:
             p, consider_lock_dead_if_created_before=p.stat().st_mtime + 1
         )
 
-    def test_rmtree(self, tmp_path):
+    def test_cleanup_ignores_symlink(self, tmp_path):
+        the_symlink = tmp_path / (self.PREFIX + "current")
+        attempt_symlink_to(the_symlink, tmp_path / (self.PREFIX + "5"))
+        self._do_cleanup(tmp_path)
+
+    def test_removal_accepts_lock(self, tmp_path):
+        folder = pathlib.make_numbered_dir(root=tmp_path, prefix=self.PREFIX)
+        pathlib.create_cleanup_lock(folder)
+        pathlib.maybe_delete_a_numbered_dir(folder)
+        assert folder.is_dir()
+
+
+class TestRmRf:
+    def test_rm_rf(self, tmp_path):
         from _pytest.pathlib import rm_rf
 
         adir = tmp_path / "adir"
@@ -328,7 +341,7 @@ class TestNumberedDir:
         rm_rf(adir)
         assert not adir.exists()
 
-    def test_rmtree_with_read_only_file(self, tmp_path):
+    def test_rm_rf_with_read_only_file(self, tmp_path):
         """Ensure rm_rf can remove directories with read-only files in them (#5524)"""
         from _pytest.pathlib import rm_rf
 
@@ -337,14 +350,17 @@ class TestNumberedDir:
 
         fn.touch()
 
-        mode = os.stat(str(fn)).st_mode
-        os.chmod(str(fn), mode & ~stat.S_IWRITE)
+        self.chmod_r(fn)
 
         rm_rf(fn.parent)
 
         assert not fn.parent.is_dir()
 
-    def test_rmtree_with_read_only_directory(self, tmp_path):
+    def chmod_r(self, path):
+        mode = os.stat(str(path)).st_mode
+        os.chmod(str(path), mode & ~stat.S_IWRITE)
+
+    def test_rm_rf_with_read_only_directory(self, tmp_path):
         """Ensure rm_rf can remove read-only directories (#5524)"""
         from _pytest.pathlib import rm_rf
 
@@ -352,23 +368,37 @@ class TestNumberedDir:
         adir.mkdir()
 
         (adir / "foo.txt").touch()
-        mode = os.stat(str(adir)).st_mode
-        os.chmod(str(adir), mode & ~stat.S_IWRITE)
+        self.chmod_r(adir)
 
         rm_rf(adir)
 
         assert not adir.is_dir()
 
-    def test_cleanup_ignores_symlink(self, tmp_path):
-        the_symlink = tmp_path / (self.PREFIX + "current")
-        attempt_symlink_to(the_symlink, tmp_path / (self.PREFIX + "5"))
-        self._do_cleanup(tmp_path)
+    def test_on_rm_rf_error(self, tmp_path):
+        from _pytest.pathlib import on_rm_rf_error
 
-    def test_removal_accepts_lock(self, tmp_path):
-        folder = pathlib.make_numbered_dir(root=tmp_path, prefix=self.PREFIX)
-        pathlib.create_cleanup_lock(folder)
-        pathlib.maybe_delete_a_numbered_dir(folder)
-        assert folder.is_dir()
+        adir = tmp_path / "dir"
+        adir.mkdir()
+
+        fn = adir / "foo.txt"
+        fn.touch()
+        self.chmod_r(fn)
+
+        # unknown exception
+        with pytest.warns(pytest.PytestWarning):
+            exc_info = (None, RuntimeError(), None)
+            on_rm_rf_error(os.unlink, str(fn), exc_info, start_path=tmp_path)
+            assert fn.is_file()
+
+        # unknown function
+        with pytest.warns(pytest.PytestWarning):
+            exc_info = (None, PermissionError(), None)
+            on_rm_rf_error(None, str(fn), exc_info, start_path=tmp_path)
+            assert fn.is_file()
+
+        exc_info = (None, PermissionError(), None)
+        on_rm_rf_error(os.unlink, str(fn), exc_info, start_path=tmp_path)
+        assert not fn.is_file()
 
 
 def attempt_symlink_to(path, to_path):