bpo-42260: PyConfig_Read() only parses argv once (GH-23168)

The PyConfig_Read() function now only parses PyConfig.argv arguments
once: PyConfig.parse_argv is set to 2 after arguments are parsed.
Since Python arguments are strippped from PyConfig.argv, parsing
arguments twice would parse the application options as Python
options.

* Rework the PyConfig documentation.
* Fix _testinternalcapi.set_config() error handling.
* SetConfigTests no longer needs parse_argv=0 when restoring the old
  configuration.

1 files changed, 7 insertions, 1 deletions

diff --git a/Lib/test/_test_embed_set_config.py b/Lib/test/_test_embed_set_config.py
index 7c91381..a19f8db 100644
--- a/Lib/test/_test_embed_set_config.py
+++ b/Lib/test/_test_embed_set_config.py
@@ -20,7 +20,7 @@ class SetConfigTests(unittest.TestCase):
         self.sys_copy = dict(sys.__dict__)
 
     def tearDown(self):
-        self.set_config(parse_argv=0)
+        _testinternalcapi.set_config(self.old_config)
         sys.__dict__.clear()
         sys.__dict__.update(self.sys_copy)
 
@@ -234,6 +234,12 @@ class SetConfigTests(unittest.TestCase):
         self.assertEqual(sys.argv, ['python_program', 'args'])
         self.assertEqual(sys.orig_argv, ['orig', 'orig_args'])
 
+        self.set_config(parse_argv=0,
+                        argv=[],
+                        orig_argv=[])
+        self.assertEqual(sys.argv, [''])
+        self.assertEqual(sys.orig_argv, [])
+
     def test_pycache_prefix(self):
         self.check(pycache_prefix=None)
         self.check(pycache_prefix="pycache_prefix")