From 494360afd00dc8f6b549f160525c3e86ec14905d Mon Sep 17 00:00:00 2001 From: Beomsoo Kim Date: Tue, 12 Nov 2024 09:11:40 +0900 Subject: [PATCH] gh-58749: Remove incorrect language spec claims about the global statement (GH-126523) * Removes erroneous explanation of the `global` statement restrictions; a name declared as global can be subsequently bound using any kind of name binding operation. * Updates `test_global.py` to also test various name-binding scenarios for global variables to ensure correct behavior --- Doc/reference/simple_stmts.rst | 21 +--- Lib/test/test_global.py | 215 ++++++++++++++++++++++++++++----- Misc/ACKS | 1 + 3 files changed, 192 insertions(+), 45 deletions(-) diff --git a/Doc/reference/simple_stmts.rst b/Doc/reference/simple_stmts.rst index 24df4a6ba7b..a005395bfc4 100644 --- a/Doc/reference/simple_stmts.rst +++ b/Doc/reference/simple_stmts.rst @@ -966,25 +966,14 @@ The :keyword:`!global` statement .. productionlist:: python-grammar global_stmt: "global" `identifier` ("," `identifier`)* -The :keyword:`global` statement is a declaration which holds for the entire -current code block. It means that the listed identifiers are to be interpreted -as globals. It would be impossible to assign to a global variable without +The :keyword:`global` causes the listed identifiers to be interpreted +as globals. It would be impossible to assign to a global variable without :keyword:`!global`, although free variables may refer to globals without being declared global. -Names listed in a :keyword:`global` statement must not be used in the same code -block textually preceding that :keyword:`!global` statement. - -Names listed in a :keyword:`global` statement must not be defined as formal -parameters, or as targets in :keyword:`with` statements or :keyword:`except` clauses, or in a :keyword:`for` target list, :keyword:`class` -definition, function definition, :keyword:`import` statement, or -:term:`variable annotations `. - -.. impl-detail:: - - The current implementation does not enforce some of these restrictions, but - programs should not abuse this freedom, as future implementations may enforce - them or silently change the meaning of the program. +The global statement applies to the entire scope of a function or +class body. A :exc:`SyntaxError` is raised if a variable is used or +assigned to prior to its global declaration in the scope. .. index:: pair: built-in function; exec diff --git a/Lib/test/test_global.py b/Lib/test/test_global.py index f5b38c25ea0..11d0bd54e8b 100644 --- a/Lib/test/test_global.py +++ b/Lib/test/test_global.py @@ -1,7 +1,19 @@ -"""Verify that warnings are issued for global statements following use.""" +"""This module includes tests for syntax errors that occur when a name +declared as `global` is used in ways that violate the language +specification, such as after assignment, usage, or annotation. The tests +verify that syntax errors are correctly raised for improper `global` +statements following variable use or assignment within functions. +Additionally, it tests various name-binding scenarios for global +variables to ensure correct behavior. +See `test_scope.py` for additional related behavioral tests covering +variable scoping and usage in different contexts. +""" + +import contextlib from test.support import check_syntax_error from test.support.warnings_helper import check_warnings +from types import SimpleNamespace import unittest import warnings @@ -12,40 +24,185 @@ class GlobalTests(unittest.TestCase): self.enterContext(check_warnings()) warnings.filterwarnings("error", module="") - def test1(self): - prog_text_1 = """\ -def wrong1(): - a = 1 - b = 2 - global a - global b -""" - check_syntax_error(self, prog_text_1, lineno=4, offset=5) + ###################################################### + ### Syntax error cases as covered in Python/symtable.c + ###################################################### - def test2(self): - prog_text_2 = """\ -def wrong2(): - print(x) - global x + def test_name_param(self): + prog_text = """\ +def fn(name_param): + global name_param """ - check_syntax_error(self, prog_text_2, lineno=3, offset=5) + check_syntax_error(self, prog_text, lineno=2, offset=5) - def test3(self): + def test_name_after_assign(self): + prog_text = """\ +def fn(): + name_assign = 1 + global name_assign +""" + check_syntax_error(self, prog_text, lineno=3, offset=5) + + def test_name_after_use(self): + prog_text = """\ +def fn(): + print(name_use) + global name_use +""" + check_syntax_error(self, prog_text, lineno=3, offset=5) + + def test_name_annot(self): prog_text_3 = """\ -def wrong3(): - print(x) - x = 2 - global x +def fn(): + name_annot: int + global name_annot """ - check_syntax_error(self, prog_text_3, lineno=4, offset=5) + check_syntax_error(self, prog_text_3, lineno=3, offset=5) - def test4(self): - prog_text_4 = """\ -global x -x = 2 -""" - # this should work - compile(prog_text_4, "", "exec") + ############################################################# + ### Tests for global variables across all name binding cases, + ### as described in executionmodel.rst + ############################################################# + + def test_assignment_statement(self): + global name_assignment_statement + value = object() + name_assignment_statement = value + self.assertIs(globals()["name_assignment_statement"], value) + del name_assignment_statement + + def test_unpacking_assignment(self): + global name_unpacking_assignment + value = object() + _, name_unpacking_assignment = [None, value] + self.assertIs(globals()["name_unpacking_assignment"], value) + del name_unpacking_assignment + + def test_assignment_expression(self): + global name_assignment_expression + value = object() + if name_assignment_expression := value: + pass + self.assertIs(globals()["name_assignment_expression"], value) + del name_assignment_expression + + def test_iteration_variable(self): + global name_iteration_variable + value = object() + for name_iteration_variable in [value]: + pass + self.assertIs(globals()["name_iteration_variable"], value) + del name_iteration_variable + + def test_func_def(self): + global name_func_def + + def name_func_def(): + pass + + value = name_func_def + self.assertIs(globals()["name_func_def"], value) + del name_func_def + + def test_class_def(self): + global name_class_def + + class name_class_def: + pass + + value = name_class_def + self.assertIs(globals()["name_class_def"], value) + del name_class_def + + def test_type_alias(self): + global name_type_alias + type name_type_alias = tuple[int, int] + value = name_type_alias + self.assertIs(globals()["name_type_alias"], value) + del name_type_alias + + def test_caught_exception(self): + global name_caught_exc + + try: + 1 / 0 + except ZeroDivisionError as name_caught_exc: + value = name_caught_exc + # `name_caught_exc` is cleared automatically after the except block + self.assertIs(globals()["name_caught_exc"], value) + + def test_caught_exception_group(self): + global name_caught_exc_group + try: + try: + 1 / 0 + except ZeroDivisionError as exc: + raise ExceptionGroup("eg", [exc]) + except* ZeroDivisionError as name_caught_exc_group: + value = name_caught_exc_group + # `name_caught_exc` is cleared automatically after the except block + self.assertIs(globals()["name_caught_exc_group"], value) + + def test_enter_result(self): + global name_enter_result + value = object() + with contextlib.nullcontext(value) as name_enter_result: + pass + self.assertIs(globals()["name_enter_result"], value) + del name_enter_result + + def test_import_result(self): + global name_import_result + value = contextlib + import contextlib as name_import_result + + self.assertIs(globals()["name_import_result"], value) + del name_import_result + + def test_match(self): + global name_match + value = object() + match value: + case name_match: + pass + self.assertIs(globals()["name_match"], value) + del name_match + + def test_match_as(self): + global name_match_as + value = object() + match value: + case _ as name_match_as: + pass + self.assertIs(globals()["name_match_as"], value) + del name_match_as + + def test_match_seq(self): + global name_match_seq + value = object() + match (None, value): + case (_, name_match_seq): + pass + self.assertIs(globals()["name_match_seq"], value) + del name_match_seq + + def test_match_map(self): + global name_match_map + value = object() + match {"key": value}: + case {"key": name_match_map}: + pass + self.assertIs(globals()["name_match_map"], value) + del name_match_map + + def test_match_attr(self): + global name_match_attr + value = object() + match SimpleNamespace(key=value): + case SimpleNamespace(key=name_match_attr): + pass + self.assertIs(globals()["name_match_attr"], value) + del name_match_attr def setUpModule(): diff --git a/Misc/ACKS b/Misc/ACKS index 1a25088052f..6b5d7bf80ce 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -953,6 +953,7 @@ Sanyam Khurana Tyler Kieft Mads Kiilerich Jason Killen +Beomsoo Bombs Kim Derek D. Kim Gihwan Kim Jan Kim