Merge pull request #46 from pypa/bpo-44497/symlink-infinite-recursion

Avoid symlink infinite loops (separate concerns + repro)

Author: jaraco

distutils/filelist.py

@@ -247,14 +247,41 @@ def _find_all_simple(path):
     """
     Find all files under 'path'
     """
+    all_unique = _UniqueDirs.filter(os.walk(path, followlinks=True))
     results = (
         os.path.join(base, file)
-        for base, dirs, files in os.walk(path, followlinks=True)
+        for base, dirs, files in all_unique
         for file in files
     )
     return filter(os.path.isfile, results)
 
 
+class _UniqueDirs(set):
+    """
+    Exclude previously-seen dirs from walk results,
+    avoiding infinite recursion.
+    Ref https://bugs.python.org/issue44497.
+    """
+    def __call__(self, walk_item):
+        """
+        Given an item from an os.walk result, determine
+        if the item represents a unique dir for this instance
+        and if not, prevent further traversal.
+        """
+        base, dirs, files = walk_item
+        stat = os.stat(base)
+        candidate = stat.st_dev, stat.st_ino
+        found = candidate in self
+        if found:
+            del dirs[:]
+        self.add(candidate)
+        return not found
+
+    @classmethod
+    def filter(cls, items):
+        return filter(cls(), items)
+
+
 def findall(dir=os.curdir):
     """
     Find all files under 'dir' and return the list of full filenames.

distutils/tests/test_filelist.py

@@ -331,6 +331,16 @@ def test_non_local_discovery(self):
             expected = [file1]
             self.assertEqual(filelist.findall(temp_dir), expected)
 
+    @os_helper.skip_unless_symlink
+    def test_symlink_loop(self):
+        with os_helper.temp_dir() as temp_dir:
+            link = os.path.join(temp_dir, 'link-to-parent')
+            content = os.path.join(temp_dir, 'somefile')
+            os_helper.create_empty_file(content)
+            os.symlink('.', link)
+            files = filelist.findall(temp_dir)
+            assert len(files) == 1
+
 
 def test_suite():
     return unittest.TestSuite([