bpo-22490: Remove __PYVENV_LAUNCHER__ from environment during launch (GH-9516)

* bpo-22490: Remove "__PYVENV_LAUNCHER__" from the shell environment on macOS

This changeset removes the environment varialbe "__PYVENV_LAUNCHER__"
during interpreter launch as it is only needed to communicate between
the stub executable in framework installs and the actual interpreter.

Leaving the environment variable present may lead to misbehaviour when
launching other scripts.

* Actually commit the changes for issue 22490...

* Correct typo

Co-Authored-By: Nicola Soranzo <nicola.soranzo@gmail.com>

* Run make patchcheck

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>
Co-authored-by: Nicola Soranzo <nicola.soranzo@gmail.com>

Lib/test/test_subprocess.py

@@ -682,7 +682,6 @@ class ProcessTestCase(BaseTestCase):
             # on adding even when the environment in exec is empty.
             # Gentoo sandboxes also force LD_PRELOAD and SANDBOX_* to exist.
             return ('VERSIONER' in n or '__CF' in n or  # MacOS
-                    '__PYVENV_LAUNCHER__' in n or # MacOS framework build
                     n == 'LD_PRELOAD' or n.startswith('SANDBOX') or # Gentoo
                     n == 'LC_CTYPE') # Locale coercion triggered
 

Lib/test/test_venv.py

@@ -391,6 +391,18 @@ class BasicTest(BaseTest):
         self.assertEqual(err, "".encode())
 
 
+    @unittest.skipUnless(sys.platform == 'darwin', 'only relevant on macOS')
+    def test_macos_env(self):
+        rmtree(self.env_dir)
+        builder = venv.EnvBuilder()
+        builder.create(self.env_dir)
+
+        envpy = os.path.join(os.path.realpath(self.env_dir),
+                             self.bindir, self.exe)
+        out, err = check_output([envpy, '-c',
+            'import os; print("__PYVENV_LAUNCHER__" in os.environ)'])
+        self.assertEqual(out.strip(), 'False'.encode())
+
 @requireVenvCreate
 class EnsurePipTest(BaseTest):
     """Test venv module installation of pip."""

Mac/Tools/pythonw.c

@@ -196,6 +196,15 @@ main(int argc, char **argv) {
             }
         }
 
+        /*
+         * The environment variable is used to pass the value of real_path
+         * to the actual python interpreter, and is read by code in
+         * Python/coreconfig.c.
+         *
+         * This way the real interpreter knows how the user invoked the
+         * interpreter and can behave as if this launcher is the real
+         * interpreter (looking for pyvenv configuration, ...)
+         */
         setenv("__PYVENV_LAUNCHER__", real_path, 1);
     }
 

Misc/NEWS.d/next/Core and Builtins/2018-09-23-16-32-58.bpo-22490.8e0YDf.rst

@@ -0,0 +1,2 @@
+Don't leak environment variable ``__PYVENV_LAUNCHER__`` into the interpreter
+session on macOS.

Python/initconfig.c

@@ -1139,6 +1139,17 @@ config_init_program_name(PyConfig *config)
             if (_PyStatus_EXCEPTION(status)) {
                 return status;
             }
+
+            /*
+             * This environment variable is used to communicate between
+             * the stub launcher and the real interpreter and isn't needed
+             * beyond this point.
+             *
+             * Clean up to avoid problems when launching other programs
+             * later on.
+             */
+            (void)unsetenv("__PYVENV_LAUNCHER__");
+
             return _PyStatus_OK();
         }
     }