Skip unreadable dirs in recursive file walk (closes #3)

dol/filesys.py

@@ -41,7 +41,11 @@ def paths_in_dir(rootdir, include_hidden=False):
                     yield ensure_slash_suffix(filepath)
                 else:
                     yield filepath
-    except FileNotFoundError:
+    except (FileNotFoundError, NotADirectoryError, PermissionError):
+        # Skip directories that vanished, aren't directories, or aren't readable rather
+        # than crashing the (recursive) walk. Notably, OS-protected directories such as
+        # macOS's ``.../com.apple.*/TemporaryItems/`` under the temp dir raise
+        # PermissionError from ``os.listdir`` (Issue #3).
         pass
 
 

dol/tests/test_walk_permissions.py

@@ -0,0 +1,47 @@
+"""Regression test for Issue #3: the recursive file walk must skip unreadable dirs.
+
+``FileBytesReader(gettempdir())`` used to raise ``PermissionError`` because ``os.listdir``
+hits OS-protected subdirectories (e.g. macOS's ``.../com.apple.*/TemporaryItems/``). The
+walk now skips directories it cannot read instead of crashing.
+"""
+
+import os
+import sys
+
+import pytest
+
+from dol.filesys import FileBytesReader, paths_in_dir
+
+
+def test_recursive_walk_skips_unreadable_dirs(tmp_path):
+    # a readable file at the root
+    (tmp_path / "readable.txt").write_bytes(b"hi")
+    # a subdirectory we will make unreadable
+    protected = tmp_path / "protected"
+    protected.mkdir()
+    (protected / "secret.txt").write_bytes(b"nope")
+
+    if sys.platform.startswith("win"):
+        pytest.skip("POSIX directory permissions don't apply on Windows")
+
+    os.chmod(protected, 0o000)
+    try:
+        # If we can still list it (e.g. running as root), the scenario is unreachable.
+        try:
+            os.listdir(protected)
+            pytest.skip("cannot make a directory unreadable in this environment")
+        except PermissionError:
+            pass
+
+        # The walk must not raise, and must skip the unreadable subdir's contents.
+        s = FileBytesReader(str(tmp_path))
+        keys = list(s)  # was: PermissionError
+        assert any(k.endswith("readable.txt") for k in keys)
+        assert not any(k.endswith("secret.txt") for k in keys)
+    finally:
+        os.chmod(protected, 0o755)  # restore so tmp cleanup can remove it
+
+
+def test_paths_in_dir_on_missing_dir_is_empty(tmp_path):
+    missing = str(tmp_path / "does_not_exist")
+    assert list(paths_in_dir(missing)) == []