bpo-40939: Remove the old parser (pythonGH-20768)

This commit removes the old parser, the deprecated parser module, the old parser compatibility flags and environment variables and all associated support code and documentation.

Author: pablogsal

Doc/c-api/init_config.rst

@@ -695,16 +695,6 @@ PyConfig
 
       :data:`sys._xoptions`.
 
-   .. c:member:: int _use_peg_parser
-
-      Enable PEG parser? Default: 1.
-
-      Set to 0 by :option:`-X oldparser <-X>` and :envvar:`PYTHONOLDPARSER`.
-
-      See also :pep:`617`.
-
-      .. deprecated-removed:: 3.9 3.10
-
 If ``parse_argv`` is non-zero, ``argv`` arguments are parsed the same
 way the regular Python parses command line arguments, and Python
 arguments are stripped from ``argv``: see :ref:`Command Line Arguments

Doc/using/cmdline.rst

@@ -426,8 +426,6 @@ Miscellaneous options
    defines the following possible values:
 
    * ``-X faulthandler`` to enable :mod:`faulthandler`;
-   * ``-X oldparser``: enable the traditional LL(1) parser.  See also
-     :envvar:`PYTHONOLDPARSER` and :pep:`617`.
    * ``-X showrefcount`` to output the total reference count and number of used
      memory blocks when the program finishes or after each statement in the
      interactive interpreter. This only works on debug builds.
@@ -587,15 +585,6 @@ conflict.
    :option:`-d` multiple times.
 
 
-.. envvar:: PYTHONOLDPARSER
-
-   If this is set to a non-empty string, enable the traditional LL(1) parser.
-
-   See also the :option:`-X` ``oldparser`` option and :pep:`617`.
-
-   .. deprecated-removed:: 3.9 3.10
-
-
 .. envvar:: PYTHONINSPECT
 
    If this is set to a non-empty string it is equivalent to specifying the

Include/cpython/initconfig.h

@@ -144,10 +144,6 @@ typedef struct {
        Set to 1 by -X faulthandler and PYTHONFAULTHANDLER. -1 means unset. */
     int faulthandler;
 
-    /* Enable PEG parser?
-       1 by default, set to 0 by -X oldparser and PYTHONOLDPARSER */
-    int _use_peg_parser;
-
     /* Enable tracemalloc?
        Set by -X tracemalloc=N and PYTHONTRACEMALLOC. -1 means unset */
     int tracemalloc;

Lib/subprocess.py

@@ -326,7 +326,7 @@ def _args_from_interpreter_flags():
     if dev_mode:
         args.extend(('-X', 'dev'))
     for opt in ('faulthandler', 'tracemalloc', 'importtime',
-                'showrefcount', 'utf8', 'oldparser'):
+                'showrefcount', 'utf8'):
         if opt in xoptions:
             value = xoptions[opt]
             if value is True:

Lib/test/support/__init__.py

@@ -1958,13 +1958,3 @@ def wait_process(pid, *, exitcode, timeout=None):
     # sanity check: it should not fail in practice
     if pid2 != pid:
         raise AssertionError(f"pid {pid2} != pid {pid}")
-
-
-def use_old_parser():
-    import _testinternalcapi
-    config = _testinternalcapi.get_configs()
-    return (config['config']['_use_peg_parser'] == 0)
-
-
-def skip_if_new_parser(msg):
-    return unittest.skipIf(not use_old_parser(), msg)

Lib/test/test_embed.py

@@ -347,7 +347,6 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'isolated': 0,
         'use_environment': 1,
         'dev_mode': 0,
-        '_use_peg_parser': 1,
 
         'install_signal_handlers': 1,
         'use_hash_seed': 0,
@@ -733,7 +732,6 @@ def test_init_from_config(self):
             'import_time': 1,
             'show_ref_count': 1,
             'malloc_stats': 1,
-            '_use_peg_parser': 0,
 
             'stdio_encoding': 'iso8859-1',
             'stdio_errors': 'replace',
@@ -807,7 +805,6 @@ def test_init_compat_env(self):
             'warnoptions': ['EnvVar'],
             'platlibdir': 'env_platlibdir',
             'module_search_paths': self.IGNORE_CONFIG,
-            '_use_peg_parser': 0,
         }
         self.check_all_configs("test_init_compat_env", config, preconfig,
                                api=API_COMPAT)
@@ -837,7 +834,6 @@ def test_init_python_env(self):
             'warnoptions': ['EnvVar'],
             'platlibdir': 'env_platlibdir',
             'module_search_paths': self.IGNORE_CONFIG,
-            '_use_peg_parser': 0,
         }
         self.check_all_configs("test_init_python_env", config, preconfig,
                                api=API_PYTHON)

Lib/test/test_exceptions.py

@@ -251,9 +251,9 @@ def baz():
         check('def f():\n  x, y: int', 2, 3)
         check('[*x for x in xs]', 1, 2)
         check('foo(x for x in range(10), 100)', 1, 5)
-        check('(yield i) = 2', 1, 1 if support.use_old_parser() else 2)
-        check('def f(*):\n  pass', 1, 7 if support.use_old_parser() else 8)
-        check('for 1 in []: pass', 1, 5 if support.use_old_parser() else 7)
+        check('(yield i) = 2', 1, 2)
+        check('def f(*):\n  pass', 1, 8)
+        check('for 1 in []: pass', 1, 7)
 
     @cpython_only
     def testSettingException(self):

Lib/test/test_flufl.py

@@ -20,7 +20,7 @@ def test_barry_as_bdfl(self):
         self.assertTrue(cm.exception.lineno, 2)
         # The old parser reports the end of the token and the new
         # parser reports the start of the token
-        self.assertEqual(cm.exception.offset, 4 if support.use_old_parser() else 3)
+        self.assertEqual(cm.exception.offset, 3)
 
     def test_guido_as_bdfl(self):
         code = '2 {0} 3'
@@ -33,7 +33,7 @@ def test_guido_as_bdfl(self):
         self.assertEqual(cm.exception.lineno, 1)
         # The old parser reports the end of the token and the new
         # parser reports the start of the token
-        self.assertEqual(cm.exception.offset, 4 if support.use_old_parser() else 3)
+        self.assertEqual(cm.exception.offset, 3)
 
 
 if __name__ == '__main__':

Lib/test/test_fstring.py

@@ -12,7 +12,7 @@
 import types
 import decimal
 import unittest
-from test.support import temp_cwd, use_old_parser
+from test.support import temp_cwd
 from test.support.script_helper import assert_python_failure
 
 a_global = 'global variable'
@@ -1049,7 +1049,6 @@ def test_errors(self):
                              r"f'{1000:j}'",
                             ])
 
-    @unittest.skipIf(use_old_parser(), "The old parser only supports <fstring> as the filename")
     def test_filename_in_syntaxerror(self):
         # see issue 38964
         with temp_cwd() as cwd:

Lib/test/test_grammar.py

@@ -1,7 +1,7 @@
 # Python test set -- part 1, grammar.
 # This just tests whether the parser accepts them all.
 
-from test.support import check_syntax_error, check_syntax_warning, use_old_parser
+from test.support import check_syntax_error, check_syntax_warning
 import inspect
 import unittest
 import sys
@@ -1714,69 +1714,53 @@ def __exit__(self, *args):
         with manager() as x, manager():
             pass
 
-        if not use_old_parser():
-            test_cases = [
-                """if 1:
-                    with (
-                        manager()
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager() as x
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager() as (x, y),
-                        manager() as z,
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager(),
-                        manager()
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager() as x,
-                        manager() as y
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager() as x,
-                        manager()
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager() as x,
-                        manager() as y,
-                        manager() as z,
-                    ):
-                        pass
-                """,
-                """if 1:
-                    with (
-                        manager() as x,
-                        manager() as y,
-                        manager(),
-                    ):
-                        pass
-                """,
-            ]
-            for case in test_cases:
-                with self.subTest(case=case):
-                    compile(case, "<string>", "exec")
+        with (
+            manager()
+        ):
+            pass
+
+        with (
+            manager() as x
+        ):
+            pass
+
+        with (
+            manager() as (x, y),
+            manager() as z,
+        ):
+            pass
+
+        with (
+            manager(),
+            manager()
+        ):
+            pass
 
+        with (
+            manager() as x,
+            manager() as y
+        ):
+            pass
+
+        with (
+            manager() as x,
+            manager()
+        ):
+            pass
+
+        with (
+            manager() as x,
+            manager() as y,
+            manager() as z,
+        ):
+            pass
+
+        with (
+            manager() as x,
+            manager() as y,
+            manager(),
+        ):
+            pass
 
     def test_if_else_expr(self):
         # Test ifelse expressions in various cases