From 270e2492900275fe2ec93c7982fa175ed132e6b9 Mon Sep 17 00:00:00 2001 From: Pablo Galindo Date: Thu, 3 Sep 2020 16:35:36 +0100 Subject: [3.9] Fix 'gather' rules in the python parser generator (GH-22021) (GH-22080) Currently, empty sequences in gather rules make the conditional for gather rules fail as empty sequences evaluate as "False". We need to explicitly check for "None" (the failure condition) to avoid false negatives. (cherry picked from commit e55a0e9) Co-authored-by: Pablo Galindo --- Lib/test/test_peg_generator/test_pegen.py | 16 +++++++++++++++- Tools/peg_generator/pegen/python_generator.py | 3 +++ 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/Lib/test/test_peg_generator/test_pegen.py b/Lib/test/test_peg_generator/test_pegen.py index 5b4e964..bcfee3f 100644 --- a/Lib/test/test_peg_generator/test_pegen.py +++ b/Lib/test/test_peg_generator/test_pegen.py @@ -74,7 +74,7 @@ class TestPegen(unittest.TestCase): "Rule('term', 'int', Rhs([Alt([NamedItem(None, NameLeaf('NUMBER'))])]))" ) - def test_repeat_with_separator_rules(self) -> None: + def test_gather(self) -> None: grammar = """ start: ','.thing+ NEWLINE thing: NUMBER @@ -85,6 +85,20 @@ class TestPegen(unittest.TestCase): "Rule('start', None, Rhs([Alt([NamedItem(None, Gather(StringLeaf(\"','\"), NameLeaf('thing'" )) self.assertEqual(str(rules["thing"]), "thing: NUMBER") + parser_class = make_parser(grammar) + node = parse_string("42\n", parser_class) + assert node == [ + [[TokenInfo(NUMBER, string="42", start=(1, 0), end=(1, 2), line="42\n")]], + TokenInfo(NEWLINE, string="\n", start=(1, 2), end=(1, 3), line="42\n"), + ] + node = parse_string("1, 2\n", parser_class) + assert node == [ + [ + [TokenInfo(NUMBER, string="1", start=(1, 0), end=(1, 1), line="1, 2\n")], + [TokenInfo(NUMBER, string="2", start=(1, 3), end=(1, 4), line="1, 2\n")], + ], + TokenInfo(NEWLINE, string="\n", start=(1, 4), end=(1, 5), line="1, 2\n"), + ] def test_expr_grammar(self) -> None: grammar = """ diff --git a/Tools/peg_generator/pegen/python_generator.py b/Tools/peg_generator/pegen/python_generator.py index 45a7597..b786de7 100644 --- a/Tools/peg_generator/pegen/python_generator.py +++ b/Tools/peg_generator/pegen/python_generator.py @@ -217,6 +217,9 @@ class PythonParserGenerator(ParserGenerator, GrammarVisitor): else: self.print("and") self.visit(item) + if is_gather: + self.print("is not None") + self.print("):") with self.indent(): action = node.action -- cgit v0.12