Correct the order of operations to ensure that failed attempts aren't…

… cached and are thus retried on subsequent operations.

Closes pypa#304

distutils/dir_util.py

@@ -32,8 +32,9 @@ def wrap(self, func):
         def wrapper(path, *args, **kwargs):
             if path.absolute() in self:
                 return
+            result = func(path, *args, **kwargs)
             self.add(path.absolute())
-            return func(path, *args, **kwargs)
+            return result
 
         return wrapper
 

distutils/tests/test_dir_util.py

@@ -112,7 +112,6 @@ def test_copy_tree_exception_in_listdir(self):
             src = self.tempdirs[-1]
             dir_util.copy_tree(src, None)
 
-    @pytest.mark.xfail(reason="#304")
     def test_mkpath_exception_uncached(self, monkeypatch, tmp_path):
         """
         Caching should not remember failed attempts.