Fails to parse parenthesized with statement without trailing comma

[andersk]

#584 added parenthesized with statements to the native parser, but they’re only accepted when a trailing comma is present. Python accepts them with or without a trailing comma.

$ pip freeze
libcst==0.4.9
mypy-extensions==0.4.3
PyYAML==6.0
typing-inspect==0.8.0
typing_extensions==4.4.0

$ export LIBCST_PARSER_TYPE=native

$ python3 -c 'import libcst; libcst.parse_statement("with (a as a, b as b,): pass")'

$ python3 -c 'import libcst; libcst.parse_statement("with (a as a, b as b): pass")'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/tmp/v/lib/python3.10/site-packages/libcst/_parser/entrypoints.py", line 138, in parse_statement
    result = _parse(
  File "/tmp/v/lib/python3.10/site-packages/libcst/_parser/entrypoints.py", line 55, in _parse
    return parse(source_str)
libcst._exceptions.ParserSyntaxError: Syntax Error @ 1:1.
parser error: error at 1:20: expected *

with (a as a, b as b): pass
^

Cc @stroxler

[jakkdl]

I'm hitting this as well in https://github.com/Zac-HD/flake8-trio
It additionally also fails with newlines:
nvm, I didn't set the parser type.

[stroxler]

Thanks for the bug reports - I'll try to tackle this in the next week.

[jakkdl]

oh I'm sorry, mine is due to not having done LIBCST_PARSER_TYPE=native