From 595b516965ee88b817dc1b3d7713e1f3f263634d Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Tue, 28 Jan 2020 01:59:43 -0800
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 8ed3c883c60..015370a860e 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -253,9 +253,7 @@ class _WindowsFlavour(_Flavour):
             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 b127343982c..97fc5d8ad78 100644
--- a/Lib/test/test_pathlib.py
+++ b/Lib/test/test_pathlib.py
@@ -1296,8 +1296,16 @@ class _BasePathTest(object):
         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 @@ class WindowsPathTest(_BasePathTest, unittest.TestCase):
                 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 @@ class WindowsPathTest(_BasePathTest, unittest.TestCase):
             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 00000000000..c552e850a36
--- /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`.