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bpo-41044: Generate valid PEG python parsers for opt+seq rules (GH-20995)

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Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
(cherry picked from commit 55460ee6dc)

Co-authored-by: Batuhan Taskaya <isidentical@gmail.com>
This commit is contained in:
Miss Islington (bot) 2020-06-20 10:59:32 -07:00 • committed by GitHub
parent c9f83c173b
commit 9862181750
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2 changed files with 15 additions and 1 deletions
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8
Lib/test/test_peg_generator/test_pegen.py
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@ -493,6 +493,14 @@ class TestPegen(unittest.TestCase):
# Would assert False without a special case in compute_left_recursives().
make_parser(grammar)
def test_opt_sequence(self) -> None:
grammar = """
start: [NAME*]
"""
# This case was failing because of a double trailing comma at the end
# of a line in the generated source. See bpo-41044
make_parser(grammar)
def test_left_recursion_too_complex(self) -> None:
grammar = """
start: foo

8
Tools/peg_generator/pegen/python_generator.py
View file

@ -93,7 +93,13 @@ class PythonCallMakerVisitor(GrammarVisitor):
def visit_Opt(self, node: Opt) -> Tuple[str, str]:
name, call = self.visit(node.node)
return "opt", f"{call}," # Note trailing comma!
# Note trailing comma (the call may already have one comma
# at the end, for example when rules have both repeat0 and optional
# markers, e.g: [rule*])
if call.endswith(","):
return "opt", call
else:
return "opt", f"{call},"
def visit_Repeat0(self, node: Repeat0) -> Tuple[str, str]:
if node in self.cache: