bpo-37369: Fix initialization of sys members when launched via an app container (GH-14428)

sys._base_executable is now always defined on all platforms, and can be overridden through configuration.
Also adds test.support.PythonSymlink to encapsulate platform-specific logic for symlinking sys.executable

1 files changed, 19 insertions, 12 deletions

diff --git a/Lib/test/test_venv.py b/Lib/test/test_venv.py
index 4f6c11b266..ea016b59ae 100644
--- a/Lib/test/test_venv.py
+++ b/Lib/test/test_venv.py
@@ -28,8 +28,8 @@ except ImportError:
 # Platforms that set sys._base_executable can create venvs from within
 # another venv, so no need to skip tests that require venv.create().
 requireVenvCreate = unittest.skipUnless(
-    hasattr(sys, '_base_executable')
-    or sys.prefix == sys.base_prefix,
+    sys.prefix == sys.base_prefix
+    or sys._base_executable != sys.executable,
     'cannot run venv.create from within a venv on this platform')
 
 def check_output(cmd, encoding=None):
@@ -57,8 +57,14 @@ class BaseTest(unittest.TestCase):
             self.bindir = 'bin'
             self.lib = ('lib', 'python%d.%d' % sys.version_info[:2])
             self.include = 'include'
-        executable = getattr(sys, '_base_executable', sys.executable)
+        executable = sys._base_executable
         self.exe = os.path.split(executable)[-1]
+        if (sys.platform == 'win32'
+            and os.path.lexists(executable)
+            and not os.path.exists(executable)):
+            self.cannot_link_exe = True
+        else:
+            self.cannot_link_exe = False
 
     def tearDown(self):
         rmtree(self.env_dir)
@@ -102,7 +108,7 @@ class BasicTest(BaseTest):
         else:
             self.assertFalse(os.path.exists(p))
         data = self.get_text_file_contents('pyvenv.cfg')
-        executable = getattr(sys, '_base_executable', sys.executable)
+        executable = sys._base_executable
         path = os.path.dirname(executable)
         self.assertIn('home = %s' % path, data)
         fn = self.get_env_file(self.bindir, self.exe)
@@ -158,10 +164,6 @@ class BasicTest(BaseTest):
         """
         Test that the prefix values are as expected.
         """
-        #check our prefixes
-        self.assertEqual(sys.base_prefix, sys.prefix)
-        self.assertEqual(sys.base_exec_prefix, sys.exec_prefix)
-
         # check a venv's prefixes
         rmtree(self.env_dir)
         self.run_with_capture(venv.create, self.env_dir)
@@ -169,9 +171,9 @@ class BasicTest(BaseTest):
         cmd = [envpy, '-c', None]
         for prefix, expected in (
             ('prefix', self.env_dir),
-            ('prefix', self.env_dir),
-            ('base_prefix', sys.prefix),
-            ('base_exec_prefix', sys.exec_prefix)):
+            ('exec_prefix', self.env_dir),
+            ('base_prefix', sys.base_prefix),
+            ('base_exec_prefix', sys.base_exec_prefix)):
             cmd[2] = 'import sys; print(sys.%s)' % prefix
             out, err = check_output(cmd)
             self.assertEqual(out.strip(), expected.encode())
@@ -283,7 +285,12 @@ class BasicTest(BaseTest):
             # symlinked to 'python3.3' in the env, even when symlinking in
             # general isn't wanted.
             if usl:
-                self.assertTrue(os.path.islink(fn))
+                if self.cannot_link_exe:
+                    # Symlinking is skipped when our executable is already a
+                    # special app symlink
+                    self.assertFalse(os.path.islink(fn))
+                else:
+                    self.assertTrue(os.path.islink(fn))
 
     # If a venv is created from a source build and that venv is used to
     # run the test, the pyvenv.cfg in the venv created in the test will