Fix the protect-pip-on-windows logic

news/10560.bugfix.rst

@@ -0,0 +1 @@
+Fix conditional checks to prevent ``pip.exe`` from trying to modify itself, on Windows.

src/pip/_internal/utils/misc.py

@@ -556,9 +556,9 @@ def protect_pip_from_modification_on_windows(modifying_pip: bool) -> None:
         python -m pip ...
     """
     pip_names = [
-        "pip.exe",
-        "pip{}.exe".format(sys.version_info[0]),
-        "pip{}.{}.exe".format(*sys.version_info[:2]),
+        "pip",
+        "pip{}".format(sys.version_info[0]),
+        "pip{}.{}".format(*sys.version_info[:2]),
     ]
 
     # See https://github.com/pypa/pip/issues/1299 for more discussion

tests/functional/test_install_upgrade.py

@@ -1,5 +1,6 @@
 import itertools
 import os
+import sys
 import textwrap
 
 import pytest
@@ -411,3 +412,14 @@ def test_install_find_existing_package_canonicalize(
     )
     satisfied_message = f"Requirement already satisfied: {req2}"
     assert satisfied_message in result.stdout, str(result)
+
+
+@pytest.mark.network
+@pytest.mark.skipif(sys.platform != "win32", reason="Windows-only test")
+def test_modifying_pip_presents_error(script: PipTestEnvironment) -> None:
+    result = script.pip(
+        "install", "pip", "--force-reinstall", use_module=False, expect_error=True
+    )
+
+    assert "python.exe" in result.stderr or "python.EXE" in result.stderr, str(result)
+    assert " -m " in result.stderr, str(result)

tests/lib/__init__.py

@@ -666,7 +666,7 @@ def run(
         if expect_error and not allow_error:
             if result.returncode == 0:
                 __tracebackhide__ = True
-                raise AssertionError("Script passed unexpectedly.")
+                raise AssertionError(f"Script passed unexpectedly:\n{result}")
 
         _check_stderr(
             result.stderr,