From 4e57a77af31dd8d9f976c0ce78d97d88d5c2e51a Mon Sep 17 00:00:00 2001
From: Christoph Reiter <reiter.christoph@gmail.com>
Date: Tue, 28 Jan 2020 10:41:50 +0100
Subject: [PATCH] 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@gmail.com>
---
 Lib/pathlib.py                                |  4 +---
 Lib/test/test_pathlib.py                      | 22 ++++++++++++-------
 .../2020-01-11-22-53-55.bpo-38883.X7FRaN.rst  |  5 +++++
 3 files changed, 20 insertions(+), 11 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Windows/2020-01-11-22-53-55.bpo-38883.X7FRaN.rst

diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index 8ed3c883c60067..015370a860e656 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 b127343982ca9a..97fc5d8ad78382 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 00000000000000..c552e850a36840
--- /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`.