⚡ Bolt: 불필요한 lstat 호출 제거로 디렉토리 탐색 성능 최적화

.jules/bolt.md

@@ -60,3 +60,6 @@
 ## 2026-06-25 - [Optimize Path.exists() when paired with stat()]
 **Learning:** Checking `Path.exists()` before `Path.stat()` introduces a redundant system call because `exists()` internally uses `stat()`.
 **Action:** Rely on catching the `OSError` from `Path.stat()` to simultaneously check for existence and retrieve file attributes, saving measurable I/O overhead on large filesystems.
+## 2024-06-27 - [Avoid unnecessary lstat calls when filtering directories]
+**Learning:** During directory traversal optimization (e.g. `os.walk`), doing system calls like `os.lstat()` unconditionally just to check for symlinks causes substantial I/O overhead. In `find_candidates`, `is_symlink` was only needed if exact exclusions were configured (`excluded_exact_strs`), yet `os.lstat()` ran for every single subdirectory.
+**Action:** Always move heavy filesystem checks (`stat`, `lstat`, `realpath`) inside conditional blocks that actually require them. Don't pre-compute metadata if there's a chance the downstream logic will skip it.

media_shrinker.py

@@ -222,13 +222,13 @@ def find_candidates(
 
             d_path_str = os.path.join(dirpath_str, d)
 
-            try:
-                d_stat = os.lstat(d_path_str)
-                is_symlink = stat.S_ISLNK(d_stat.st_mode)
-            except OSError:
-                continue
-
             if excluded_exact_strs:
+                try:
+                    d_stat = os.lstat(d_path_str)
+                    is_symlink = stat.S_ISLNK(d_stat.st_mode)
+                except OSError:
+                    continue
+
                 if not is_symlink:
                     resolved_d_str = os.path.join(resolved_dir_str, d)
                 else:

tests/test_media_shrinker.py

@@ -196,7 +196,7 @@ def flaky_lstat(path):
             with patch("os.lstat", flaky_lstat):
                 candidates = [
                     p[0].relative_to(root)
-                    for p in find_candidates(root, include_under_limit=True)
+                    for p in find_candidates(root, include_under_limit=True, exclude_paths=[root / "some_exclude"])
                 ]
 
             self.assertEqual(candidates, [Path("good.mp3")])