Fix problem with deleting temporary folders on Windows

src/poetry/core/utils/helpers.py

@@ -4,6 +4,7 @@
 import shutil
 import stat
 import tempfile
+import time
 import unicodedata
 import warnings
 
@@ -42,7 +43,7 @@ def normalize_version(version: str) -> str:
 def temporary_directory(*args: Any, **kwargs: Any) -> Iterator[str]:
     name = tempfile.mkdtemp(*args, **kwargs)
     yield name
-    safe_rmtree(name)
+    robust_rmtree(name)
 
 
 def parse_requires(requires: str) -> list[str]:
@@ -90,10 +91,29 @@ def _on_rm_error(func: Any, path: str | Path, exc_info: Any) -> None:
     func(path)
 
 
-def safe_rmtree(path: str | Path) -> None:
-    if Path(path).is_symlink():
-        return os.unlink(str(path))
-
+def robust_rmtree(path: str, max_timeout: float = 1) -> None:
+    """
+    Robustly tries to delete paths.
+    Retries several times if an OSError occurs.
+    If the final attempt fails, the Exception is propagated
+    to the caller.
+    """
+    timeout = 0.001
+    while timeout < max_timeout:
+        try:
+            # both os.unlink and shutil.rmtree can throw exceptions on Windows
+            # if the files are in use when called
+            if Path(path).is_symlink():
+                os.unlink(str(path))
+            else:
+                shutil.rmtree(path)
+            return  # Only hits this on success
+        except OSError:
+            # Increase the timeout and try again
+            time.sleep(timeout)
+            timeout *= 2
+
+    # Final attempt, pass any Exceptions up to caller.
     shutil.rmtree(path, onerror=_on_rm_error)
 
 

tests/utils/test_helpers.py

@@ -1,15 +1,22 @@
 from __future__ import annotations
 
 import os
+import tempfile
 
 from pathlib import Path
 from stat import S_IREAD
+from typing import TYPE_CHECKING
 
 import pytest
 
+
+if TYPE_CHECKING:
+    from pytest_mock import MockerFixture
+
 from poetry.core.utils.helpers import combine_unicode
 from poetry.core.utils.helpers import parse_requires
 from poetry.core.utils.helpers import readme_content_type
+from poetry.core.utils.helpers import robust_rmtree
 from poetry.core.utils.helpers import temporary_directory
 
 
@@ -118,3 +125,28 @@ def test_utils_helpers_readme_content_type(
     readme: str | Path, content_type: str
 ) -> None:
     assert readme_content_type(readme) == content_type
+
+
+def test_robust_rmtree(mocker: MockerFixture) -> None:
+    mocked_rmtree = mocker.patch("shutil.rmtree")
+
+    # this should work after an initial exception
+    name = tempfile.mkdtemp()
+    mocked_rmtree.side_effect = [
+        OSError(
+            "Couldn't delete file yet, waiting for references to clear", "mocked path"
+        ),
+        None,
+    ]
+    robust_rmtree(name)
+
+    # this should give up after retrying multiple times
+    name = tempfile.mkdtemp()
+    mocked_rmtree.side_effect = OSError(
+        "Couldn't delete file yet, this error won't go away after first attempt"
+    )
+    with pytest.raises(OSError):
+        robust_rmtree(name, max_timeout=0.04)
+
+    # clear the side effect (breaks the tear-down otherwise)
+    mocked_rmtree.side_effect = None