From 5fe0a39b66c8bd57aa60ac72f4415532e6b39dab Mon Sep 17 00:00:00 2001
From: Richard Levasseur <rlevasseur@google.com>
Date: Tue, 24 Jun 2025 16:28:13 -0700
Subject: [PATCH] feat: relative venv home path

---
 Lib/test/test_getpath.py | 36 ++++++++++++++++++++++++++++++++++++
 Modules/getpath.py       |  5 ++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_getpath.py b/Lib/test/test_getpath.py
index f86df9d0d03485..01b8179358844c 100644
--- a/Lib/test/test_getpath.py
+++ b/Lib/test/test_getpath.py
@@ -354,6 +354,42 @@ def test_venv_posix(self):
         actual = getpath(ns, expected)
         self.assertEqual(expected, actual)
 
+    def test_venv_relative_home(self):
+        ns = MockPosixNamespace(
+            argv0="/somedir/venv/bin/python3",
+            PREFIX="/usr/local-fallback",
+            ENV_PATH="/usr/bin",
+        )
+
+        ns.add_known_xfile("/somedir/runtime/bin/python3")
+        ns.add_known_file("/somedir/runtime/lib/python9.8/os.py")
+        ns.add_known_dir("/somedir/runtime/lib/python9.8/lib-dynload")
+
+        ns.add_known_xfile("/somedir/venv/bin/python3")
+        # NOTE: Normally a relative symlink would be used, but the mock
+        # realpath() doesn't handle relative symlinks, so point it to
+        # where it ultimately would resolve to.
+        ns.add_known_link("/somedir/venv/bin/python3", "/somedir/runtime/bin/python3")
+        ns.add_known_file("/somedir/venv/pyvenv.cfg", [
+            "home = ../runtime/bin"
+        ])
+        expected = dict(
+            executable="/somedir/venv/bin/python3",
+            prefix="/somedir/venv",
+            exec_prefix="/somedir/venv",
+            base_executable="/somedir/runtime/bin/python3",
+            base_prefix="/somedir/runtime",
+            base_exec_prefix="/somedir/runtime",
+            module_search_paths_set=1,
+            module_search_paths=[
+                "/somedir/runtime/lib/python98.zip",
+                "/somedir/runtime/lib/python9.8",
+                "/somedir/runtime/lib/python9.8/lib-dynload",
+            ],
+        )
+        actual = getpath(ns, expected)
+        self.assertEqual(expected, actual)
+
     def test_venv_changed_name_posix(self):
         "Test a venv layout on *nix."
         ns = MockPosixNamespace(
diff --git a/Modules/getpath.py b/Modules/getpath.py
index be2210345afbda..03a3a6b27e71ba 100644
--- a/Modules/getpath.py
+++ b/Modules/getpath.py
@@ -374,10 +374,13 @@ def search_up(prefix, *landmarks, test=isfile):
             # If PYTHONHOME was set, ignore 'home' from pyvenv.cfg.
             if home:
                 break
+            value = value.strip()
+            if not isabs(value):
+                value = realpath(joinpath(venv_prefix, value))
             # Override executable_dir/real_executable_dir with the value from 'home'.
             # These values may be later used to calculate prefix/base_prefix, if a more
             # reliable source — like the runtime library (libpython) path — isn't available.
-            executable_dir = real_executable_dir = value.strip()
+            executable_dir = real_executable_dir = value
             # If base_executable — which points to the Python interpreted from
             # the base installation — isn't set (eg. when embedded), try to find
             # it in 'home'.