Resolve base_executable based on path if it ultimately points to the same file as the executable being run once symlinks are resolved

Author: pelson

Lib/test/test_getpath.py

@@ -400,7 +400,7 @@ def test_venv_non_installed_zip_path_posix(self):
         ns.add_known_file("/path/to/non-installed/lib/python9.8/os.py")
         ns.add_known_dir("/path/to/non-installed/lib/python9.8/lib-dynload")
         ns.add_known_file("/venv/pyvenv.cfg", [
-            r"home = /path/to/non-installed"
+            r"home = /path/to/non-installed/bin"
         ])
         expected = dict(
             executable="/venv/bin/python",
@@ -837,28 +837,28 @@ def test_PYTHONHOME_in_venv(self):
         ns = MockPosixNamespace(
             argv0="/venv/bin/python",
             PREFIX="/usr",
-            ENV_PYTHONHOME="/pythonhome",
+            ENV_PYTHONHOME="/pythonhome-p:/pythonhome-e",
         )
         # Setup venv
         ns.add_known_xfile("/venv/bin/python")
         ns.add_known_file("/venv/pyvenv.cfg", [
             r"home = /usr/bin"
         ])
-        # Seutup PYTHONHOME
-        ns.add_known_file("/pythonhome/lib/python9.8/os.py")
-        ns.add_known_dir("/pythonhome/lib/python9.8/lib-dynload")
+        # Setup PYTHONHOME
+        ns.add_known_file("/pythonhome-p/lib/python9.8/os.py")
+        ns.add_known_dir("/pythonhome-e/lib/python9.8/lib-dynload")
 
         expected = dict(
             executable="/venv/bin/python",
             prefix="/venv",
             exec_prefix="/venv",
-            base_prefix="/pythonhome",
-            base_exec_prefix="/pythonhome",
+            base_prefix="/pythonhome-p",
+            base_exec_prefix="/pythonhome-e",
             module_search_paths_set=1,
             module_search_paths=[
-                "/pythonhome/lib/python98.zip",
-                "/pythonhome/lib/python9.8",
-                "/pythonhome/lib/python9.8/lib-dynload",
+                "/pythonhome-p/lib/python98.zip",
+                "/pythonhome-p/lib/python9.8",
+                "/pythonhome-e/lib/python9.8/lib-dynload",
             ],
         )
         actual = getpath(ns, expected)

Modules/getpath.py

@@ -382,15 +382,23 @@ def search_up(prefix, *landmarks, test=isfile):
             # the base installation — isn't set (eg. when embedded), try to find
             # it in 'home'.
             if not base_executable:
-                # First try to resolve symlinked executables, since that may be
-                # more accurate than assuming the executable in 'home'.
+                _home_executable = joinpath(executable_dir, basename(executable))
+                _realpath_executable = None
                 try:
-                    base_executable = realpath(executable)
-                    if base_executable == executable:
-                        # No change, so probably not a link. Clear it and fall back
-                        base_executable = ''
+                    _realpath_executable = realpath(executable)
+
+                    # If the realpath of the executable identified in home is the same as
+                    # the realpath of the venv's executable use the (potentially not fully
+                    # resolved via realpath) path from home.
+                    if realpath(_home_executable) == _realpath_executable:
+                        base_executable = _home_executable
                 except OSError:
                     pass
+                if not base_executable:
+                    if _realpath_executable and _realpath_executable != executable:
+                        # Try to resolve symlinked executables, since that may be
+                        # more accurate than assuming the executable in 'home'.
+                        base_executable = _realpath_executable
                 if not base_executable:
                     base_executable = joinpath(executable_dir, basename(executable))
                     # It's possible "python" is executed from within a posix venv but that