fix(craft): count scan and stat failures so partial manifests admit it

A directory listing that fails after its open, or a child that vanishes
between scandir and stat, previously dropped content silently. Both now
increment skipped_unreadable so a partial manifest is distinguishable
from a complete one.

Author: nmgarza5

backend/onyx/server/features/build/sandbox/image/sandbox_daemon/manifest.py

@@ -115,6 +115,9 @@ def _walk_directory(walk: _Walk, dir_fd: int, prefix: str, depth: int) -> None:
                 resp.truncated = True
                 children = children[:MANIFEST_MAX_DIR_CHILDREN]
         except OSError:
+            # The listing failed after the open, so the directory's contents
+            # are unknown: admit the gap instead of looking complete.
+            resp.skipped_unreadable += 1
             return
         for child in children:
             if len(resp.entries) >= MANIFEST_MAX_ENTRIES:
@@ -126,6 +129,8 @@ def _walk_directory(walk: _Walk, dir_fd: int, prefix: str, depth: int) -> None:
             try:
                 st = child.stat(follow_symlinks=False)
             except OSError:
+                # Vanished or unreadable between scandir and stat.
+                resp.skipped_unreadable += 1
                 continue
             relative = f"{prefix}{child.name}"
             if stat.S_ISLNK(st.st_mode):

backend/tests/unit/onyx/server/features/craft/sandbox/test_outputs_manifest.py

@@ -131,6 +131,23 @@ def test_special_files_skipped(manifest_module: ModuleType, tmp_path: Path) -> N
     assert result.skipped_special == 1
 
 
+def test_unreadable_directory_counted_not_listed(
+    manifest_module: ModuleType, tmp_path: Path
+) -> None:
+    if os.geteuid() == 0:
+        pytest.skip("root bypasses directory permissions")
+    locked = tmp_path / "locked"
+    locked.mkdir()
+    (locked / "hidden.txt").write_bytes(b"x")
+    locked.chmod(0o000)
+    try:
+        result = manifest_module.build_manifest_for_root(tmp_path)
+    finally:
+        locked.chmod(0o755)
+    assert [e.path for e in result.entries] == []
+    assert result.skipped_unreadable == 1
+
+
 def test_truncation_flags_instead_of_growing(
     manifest_module: ModuleType,
     tmp_path: Path,