[Python-checkins] bpo-38883: Don't use POSIX `$HOME` in `pathlib.Path.home/expanduser` on Windows (GH-17961)

[Miss Islington (bot)]

https://github.com/python/cpython/commit/595b516965ee88b817dc1b3d7713e1f3f263634d
commit: 595b516965ee88b817dc1b3d7713e1f3f263634d
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-01-28T01:59:43-08:00
summary:

bpo-38883: Don't use POSIX `$HOME` in `pathlib.Path.home/expanduser` on Windows (GH-17961)


In bpo-36264 os.path.expanduser was changed to ignore HOME on Windows.

Path.expanduser/home still honored HOME despite being documented as behaving the same
as os.path.expanduser. This makes them also ignore HOME so that both implementations
behave the same way again.
(cherry picked from commit c45a2aa9e255b5c7c211faa79f6b23895b64ab27)

Co-authored-by: Christoph Reiter <reiter.christoph at gmail.com>

files:
A Misc/NEWS.d/next/Windows/2020-01-11-22-53-55.bpo-38883.X7FRaN.rst
M Lib/pathlib.py
M Lib/test/test_pathlib.py

diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index 8ed3c883c6006..015370a860e65 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -253,9 +253,7 @@ def make_uri(self, path):
             return 'file:' + urlquote_from_bytes(path.as_posix().encode('utf-8'))
 
     def gethomedir(self, username):
-        if 'HOME' in os.environ:
-            userhome = os.environ['HOME']
-        elif 'USERPROFILE' in os.environ:
+        if 'USERPROFILE' in os.environ:
             userhome = os.environ['USERPROFILE']
         elif 'HOMEPATH' in os.environ:
             try:
diff --git a/Lib/test/test_pathlib.py b/Lib/test/test_pathlib.py
index b127343982ca9..97fc5d8ad7838 100644
--- a/Lib/test/test_pathlib.py
+++ b/Lib/test/test_pathlib.py
@@ -1296,8 +1296,16 @@ def _test_home(self, p):
         self.assertTrue(p.is_absolute())
 
     def test_home(self):
-        p = self.cls.home()
-        self._test_home(p)
+        with support.EnvironmentVarGuard() as env:
+            self._test_home(self.cls.home())
+
+            env.clear()
+            env['USERPROFILE'] = os.path.join(BASE, 'userprofile')
+            self._test_home(self.cls.home())
+
+            # bpo-38883: ignore `HOME` when set on windows
+            env['HOME'] = os.path.join(BASE, 'home')
+            self._test_home(self.cls.home())
 
     def test_samefile(self):
         fileA_path = os.path.join(BASE, 'fileA')
@@ -2348,12 +2356,6 @@ def check():
                 self.assertEqual(p5.expanduser(), p5)
                 self.assertEqual(p6.expanduser(), p6)
 
-            # Test the first lookup key in the env vars.
-            env['HOME'] = 'C:\\Users\\alice'
-            check()
-
-            # Test that HOMEPATH is available instead.
-            env.pop('HOME', None)
             env['HOMEPATH'] = 'C:\\Users\\alice'
             check()
 
@@ -2366,6 +2368,10 @@ def check():
             env['USERPROFILE'] = 'C:\\Users\\alice'
             check()
 
+            # bpo-38883: ignore `HOME` when set on windows
+            env['HOME'] = 'C:\\Users\\eve'
+            check()
+
 
 class CompatiblePathTest(unittest.TestCase):
     """
diff --git a/Misc/NEWS.d/next/Windows/2020-01-11-22-53-55.bpo-38883.X7FRaN.rst b/Misc/NEWS.d/next/Windows/2020-01-11-22-53-55.bpo-38883.X7FRaN.rst
new file mode 100644
index 0000000000000..c552e850a3684
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2020-01-11-22-53-55.bpo-38883.X7FRaN.rst
@@ -0,0 +1,5 @@
+:meth:`~pathlib.Path.home()` and :meth:`~pathlib.Path.expanduser()` on Windows
+now prefer :envvar:`USERPROFILE` and no longer use :envvar:`HOME`, which is not
+normally set for regular user accounts. This makes them again behave like
+:func:`os.path.expanduser`, which was changed to ignore :envvar:`HOME` in 3.8,
+see :issue:`36264`.