Fix test_restore_project PermissionError on Windows (#325)

On Windows, TemporaryDirectory cleanup fails with WinError 32 when
databases.db is transiently locked (e.g. by antivirus) immediately
after being extracted from the tar backup.

- Add _rmtree_robust() that retries shutil.rmtree up to 5 times with
  exponential backoff on Windows PermissionError
- Restructure restore_project_directory so the temp dir is deleted as
  soon as shutil.copytree completes; metadata and switch logic move
  after cleanup, reducing the window during which files are held open
- Fix unclosed file handle in _restore_project_metadata (open() → with)

Author: cmutel

bw2io/backup.py

@@ -3,8 +3,10 @@
 import json
 import os
 import shutil
+import sys
 import tarfile
 import tempfile
+import time
 from pathlib import Path
 from typing import Optional, Union
 
@@ -14,6 +16,26 @@
 _METADATA_FIELDS = {"is_sourced", "revision", "data", "full_hash"}
 
 
+def _rmtree_robust(path: Path) -> None:
+    """Remove a directory tree, retrying on Windows if files are briefly locked.
+
+    On Windows, SQLite files extracted from a tarball can be transiently locked
+    by the OS (e.g. antivirus scanning) immediately after being written.  Retry
+    with exponential backoff before giving up and re-raising.
+    """
+    if sys.platform != "win32":
+        shutil.rmtree(path)
+        return
+    for attempt in range(5):
+        try:
+            shutil.rmtree(path)
+            return
+        except PermissionError:
+            if attempt == 4:
+                raise
+            time.sleep(0.1 * (2**attempt))
+
+
 def _add_project_metadata() -> None:
     fp = projects.dir / "project-metadata.json"
     data = {
@@ -34,7 +56,8 @@ def _remove_project_metadata() -> None:
 def _restore_project_metadata() -> None:
     if not (projects.dir / "project-metadata.json").is_file():
         return
-    metadata = json.load(open(projects.dir / "project-metadata.json", encoding="utf-8"))
+    with open(projects.dir / "project-metadata.json", encoding="utf-8") as f:
+        metadata = json.load(f)
     for field in _METADATA_FIELDS:
         if field in metadata:
             setattr(projects.dataset, field, metadata[field])
@@ -258,22 +281,21 @@ def get_project_name(fp):
             f"Project {project_name} already exists, set `overwrite_existing=True` to overwrite"
         )
 
-    with tempfile.TemporaryDirectory() as td:
-        extracted_path = _extract_single_directory_tarball(filepath=fp, output_dir=td)
+    _from_project_name = projects.current
+    projects.set_current(project_name, update=False)
 
-        _from_project_name = projects.current
-        projects.set_current(project_name, update=False)
+    td = Path(tempfile.mkdtemp())
+    try:
+        extracted_path = _extract_single_directory_tarball(filepath=fp_path, output_dir=td)
         shutil.copytree(extracted_path, projects.dir, dirs_exist_ok=True)
+    finally:
+        _rmtree_robust(td)
 
-        _restore_project_metadata()
-        _remove_project_metadata()
-
-        if not switch:
-            projects.set_current(_from_project_name)
-
-        print(f"Restored project: {project_name}")
+    _restore_project_metadata()
+    _remove_project_metadata()
 
-    if switch:
-        projects.set_current(project_name, update=False)
+    if not switch:
+        projects.set_current(_from_project_name)
 
+    print(f"Restored project: {project_name}")
     return project_name