Issue #19728: add private ensurepip._uninstall CLI

MvL would like to be able to preserve CPython's existing clean
uninstall behaviour on Windows before enabling the pip
installation option by default.

This private CLI means running "python -m ensurepip._uninstall"
will remove pip and setuptools before proceeding with the rest
of the uninstallation process.

If the version of pip differs from the one bootstrapped by
CPython, then the uninstallation helper will leave it alone
(just like any other pip installed packages)

2 files changed, 125 insertions, 16 deletions

diff --git a/Lib/test/test_ensurepip.py b/Lib/test/test_ensurepip.py
index abf00fd..c119327 100644
--- a/Lib/test/test_ensurepip.py
+++ b/Lib/test/test_ensurepip.py
@@ -4,6 +4,8 @@ import ensurepip
 import test.support
 import os
 import os.path
+import contextlib
+import sys
 
 
 class TestEnsurePipVersion(unittest.TestCase):
@@ -122,6 +124,79 @@ class TestBootstrap(unittest.TestCase):
     def test_altinstall_default_pip_conflict(self):
         with self.assertRaises(ValueError):
             ensurepip.bootstrap(altinstall=True, default_pip=True)
+        self.run_pip.assert_not_called()
+
+@contextlib.contextmanager
+def fake_pip(version=ensurepip._PIP_VERSION):
+    if version is None:
+        pip = None
+    else:
+        class FakePip():
+            __version__ = version
+        pip = FakePip()
+    sentinel = object()
+    orig_pip = sys.modules.get("pip", sentinel)
+    sys.modules["pip"] = pip
+    try:
+        yield pip
+    finally:
+        if orig_pip is sentinel:
+            del sys.modules["pip"]
+        else:
+            sys.modules["pip"] = orig_pip
+
+class TestUninstall(unittest.TestCase):
+
+    def setUp(self):
+        run_pip_patch = unittest.mock.patch("ensurepip._run_pip")
+        self.run_pip = run_pip_patch.start()
+        self.addCleanup(run_pip_patch.stop)
+
+    def test_uninstall_skipped_when_not_installed(self):
+        with fake_pip(None):
+            ensurepip._uninstall()
+        self.run_pip.assert_not_called()
+
+    def test_uninstall_fails_with_wrong_version(self):
+        with fake_pip("not a valid version"):
+            with self.assertRaises(RuntimeError):
+                ensurepip._uninstall()
+        self.run_pip.assert_not_called()
+
+
+    def test_uninstall(self):
+        with fake_pip():
+            ensurepip._uninstall()
+
+        self.run_pip.assert_called_once_with(
+            ["uninstall", "-y", "pip", "setuptools"]
+        )
+
+    def test_uninstall_with_verbosity_1(self):
+        with fake_pip():
+            ensurepip._uninstall(verbosity=1)
+
+        self.run_pip.assert_called_once_with(
+            ["uninstall", "-y", "-v", "pip", "setuptools"]
+        )
+
+    def test_uninstall_with_verbosity_2(self):
+        with fake_pip():
+            ensurepip._uninstall(verbosity=2)
+
+        self.run_pip.assert_called_once_with(
+            ["uninstall", "-y", "-vv", "pip", "setuptools"]
+        )
+
+    def test_uninstall_with_verbosity_3(self):
+        with fake_pip():
+            ensurepip._uninstall(verbosity=3)
+
+        self.run_pip.assert_called_once_with(
+            ["uninstall", "-y", "-vvv", "pip", "setuptools"]
+        )
+
+
 
 
 if __name__ == "__main__":
diff --git a/Lib/test/test_venv.py b/Lib/test/test_venv.py
index a92f492..c15610b 100644
--- a/Lib/test/test_venv.py
+++ b/Lib/test/test_venv.py
@@ -14,6 +14,7 @@ import sys
 import tempfile
 from test.support import (captured_stdout, captured_stderr, run_unittest,
                           can_symlink, EnvironmentVarGuard)
+import textwrap
 import unittest
 import venv
 try:
@@ -258,30 +259,31 @@ class BasicTest(BaseTest):
 @skipInVenv
 class EnsurePipTest(BaseTest):
     """Test venv module installation of pip."""
-
-    def test_no_pip_by_default(self):
-        shutil.rmtree(self.env_dir)
-        self.run_with_capture(venv.create, self.env_dir)
-        envpy = os.path.join(os.path.realpath(self.env_dir), self.bindir, self.exe)
+    def assert_pip_not_installed(self):
+        envpy = os.path.join(os.path.realpath(self.env_dir),
+                             self.bindir, self.exe)
         try_import = 'try:\n import pip\nexcept ImportError:\n print("OK")'
         cmd = [envpy, '-c', try_import]
         p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
                              stderr=subprocess.PIPE)
         out, err = p.communicate()
-        self.assertEqual(err, b"")
-        self.assertEqual(out.strip(), b"OK")
+        # We force everything to text, so unittest gives the detailed diff
+        # if we get unexpected results
+        err = err.decode("latin-1") # Force to text, prevent decoding errors
+        self.assertEqual(err, "")
+        out = out.decode("latin-1") # Force to text, prevent decoding errors
+        self.assertEqual(out.strip(), "OK")
+
+
+    def test_no_pip_by_default(self):
+        shutil.rmtree(self.env_dir)
+        self.run_with_capture(venv.create, self.env_dir)
+        self.assert_pip_not_installed()
 
     def test_explicit_no_pip(self):
         shutil.rmtree(self.env_dir)
         self.run_with_capture(venv.create, self.env_dir, with_pip=False)
-        envpy = os.path.join(os.path.realpath(self.env_dir), self.bindir, self.exe)
-        try_import = 'try:\n import pip\nexcept ImportError:\n print("OK")'
-        cmd = [envpy, '-c', try_import]
-        p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
-                             stderr=subprocess.PIPE)
-        out, err = p.communicate()
-        self.assertEqual(err, b"")
-        self.assertEqual(out.strip(), b"OK")
+        self.assert_pip_not_installed()
 
     # Temporary skip for http://bugs.python.org/issue19744
     @unittest.skipIf(ssl is None, 'pip needs SSL support')
@@ -293,7 +295,8 @@ class EnsurePipTest(BaseTest):
             # environment settings don't cause venv to fail.
             envvars["PYTHONWARNINGS"] = "e"
             # pip doesn't ignore environment variables when running in
-            # isolated mode, and we don't have an active virtualenv here
+            # isolated mode, and we don't have an active virtualenv here,
+            # we're relying on the native venv support in 3.3+
             # See http://bugs.python.org/issue19734 for details
             del envvars["PIP_REQUIRE_VIRTUALENV"]
             try:
@@ -304,6 +307,7 @@ class EnsurePipTest(BaseTest):
                 details = exc.output.decode(errors="replace")
                 msg = "{}\n\n**Subprocess Output**\n{}".format(exc, details)
                 self.fail(msg)
+        # Ensure pip is available in the virtual environment
         envpy = os.path.join(os.path.realpath(self.env_dir), self.bindir, self.exe)
         cmd = [envpy, '-Im', 'pip', '--version']
         p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
@@ -319,6 +323,36 @@ class EnsurePipTest(BaseTest):
         env_dir = os.fsencode(self.env_dir).decode("latin-1")
         self.assertIn(env_dir, out)
 
+        # http://bugs.python.org/issue19728
+        # Check the private uninstall command provided for the Windows
+        # installers works (at least in a virtual environment)
+        cmd = [envpy, '-Im', 'ensurepip._uninstall']
+        with EnvironmentVarGuard() as envvars:
+            # pip doesn't ignore environment variables when running in
+            # isolated mode, and we don't have an active virtualenv here,
+            # we're relying on the native venv support in 3.3+
+            # See http://bugs.python.org/issue19734 for details
+            del envvars["PIP_REQUIRE_VIRTUALENV"]
+            p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
+                                      stderr=subprocess.PIPE)
+            out, err = p.communicate()
+        # We force everything to text, so unittest gives the detailed diff
+        # if we get unexpected results
+        err = err.decode("latin-1") # Force to text, prevent decoding errors
+        self.assertEqual(err, "")
+        # Being really specific regarding the expected behaviour for the
+        # initial bundling phase in Python 3.4. If the output changes in
+        # future pip versions, this test can be relaxed a bit.
+        out = out.decode("latin-1") # Force to text, prevent decoding errors
+        expected_output = textwrap.dedent("""\
+                            Uninstalling pip:
+                              Successfully uninstalled pip
+                            Uninstalling setuptools:
+                              Successfully uninstalled setuptools
+                            """)
+        self.assertEqual(out, expected_output)
+        self.assert_pip_not_installed()
+
 
 def test_main():
     run_unittest(BasicTest, EnsurePipTest)