pathlib: Patch pathlib to work around some bugs (fixes #7295)

(cherry picked from 28175bbee2 by
Paolo Bonzini)

mesonbuild/_pathlib.py

@@ -0,0 +1,73 @@
+# Copyright 2021 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+'''
+    This module soly exists to work around a pathlib.resolve bug on
+    certain Windows systems:
+
+    https://github.com/mesonbuild/meson/issues/7295
+    https://bugs.python.org/issue31842
+
+    It should **never** be used directly. Instead, it is automatically
+    used when `import pathlib` is used. This is achieved by messing with
+    `sys.modules['pathlib']` in mesonmain.
+
+    Additionally, the sole purpose of this module is to work around a
+    python bug. This only bugfixes to pathlib functions and classes are
+    allowed here. Finally, this file should be removed once all upstream
+    python bugs are fixed and it is OK to tell our users to "just upgrade
+    python".
+'''
+
+import pathlib
+import os
+import platform
+
+__all__ = [
+    'PurePath',
+    'PurePosixPath',
+    'PureWindowsPath',
+    'Path',
+]
+
+PurePath = pathlib.PurePath
+PurePosixPath = pathlib.PurePosixPath
+PureWindowsPath = pathlib.PureWindowsPath
+
+# Only patch on platforms where the bug occurs
+if platform.system().lower() in {'windows'}:
+    # Can not directly inherit from pathlib.Path because the __new__
+    # operator of pathlib.Path() returns a {Posix,Windows}Path object.
+    class Path(type(pathlib.Path())):
+        def resolve(self, strict: bool = False) -> 'Path':
+            '''
+                Work around a resolve bug on certain Windows systems:
+
+                https://github.com/mesonbuild/meson/issues/7295
+                https://bugs.python.org/issue31842
+            '''
+
+            try:
+                return super().resolve(strict=strict)
+            except OSError:
+                return Path(os.path.normpath(self))
+else:
+    Path = pathlib.Path
+    PosixPath = pathlib.PosixPath
+    WindowsPath = pathlib.WindowsPath
+
+    __all__ += [
+        'PosixPath',
+        'WindowsPath',
+    ]

mesonbuild/mesonmain.py

@@ -12,7 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Work around some pathlib bugs...
+from . import _pathlib
 import sys
+sys.modules['pathlib'] = _pathlib
+
 import os.path
 import importlib
 import traceback

run_project_tests.py

@@ -14,6 +14,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Work around some pathlib bugs...
+from mesonbuild import _pathlib
+import sys
+sys.modules['pathlib'] = _pathlib
+
 from concurrent.futures import ProcessPoolExecutor, CancelledError
 from enum import Enum
 from io import StringIO
@@ -29,7 +34,6 @@ import shlex
 import shutil
 import signal
 import subprocess
-import sys
 import tempfile
 import time
 import typing as T

run_tests.py

@@ -14,8 +14,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import os
+# Work around some pathlib bugs...
+from mesonbuild import _pathlib
 import sys
+sys.modules['pathlib'] = _pathlib
+
+import os
 import time
 import shutil
 import subprocess

run_unittests.py

@@ -13,6 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Work around some pathlib bugs...
+from mesonbuild import _pathlib
+import sys
+sys.modules['pathlib'] = _pathlib
+
 import time
 import stat
 import subprocess
@@ -22,7 +27,6 @@ import tempfile
 import textwrap
 import os
 import shutil
-import sys
 import unittest
 import platform
 import pickle