KeyError: ReservedString(})

[MartinThoma]

I've tried to apply mutmut to PyPDF2 and failed. Initially I thought the issue was with mutmut ( boxed/mutmut#252 ) , but I guess it's a parso bug.

Minimal example

import parso

parso.parse('stream.write(b_(rf"\{ord_(c):0>3o}"))', error_recovery=False)

Traceback

Traceback (most recent call last):
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 180, in _add_token
    plan = stack[-1].dfa.transitions[transition]
KeyError: ReservedString(})

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/__init__.py", line 58, in parse
    return grammar.parse(code, **kwargs)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/grammar.py", line 156, in parse
    root_node = p.parse(tokens=tokens)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/python/parser.py", line 79, in parse
    return super().parse(tokens)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 129, in parse
    self._add_token(token)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 186, in _add_token
    self.error_recovery(token)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/python/parser.py", line 140, in error_recovery
    return super().error_recovery(token)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 152, in error_recovery
    raise ParserSyntaxError('SyntaxError: invalid syntax', error_leaf)
parso.parser.ParserSyntaxError: ('SyntaxError: invalid syntax', <ErrorLeaf: PythonTokenTypes.OP:'}', (1, 33)>)

Environment

$ python --version     
Python 3.10.2

>>> parso.__version__
'0.8.3'

[MartinThoma]

I could simplify it:

>>> parso.parse('rf"\{foobar:>3o}"', error_recovery=False)
Traceback (most recent call last):
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 180, in _add_token
    plan = stack[-1].dfa.transitions[transition]
KeyError: ReservedString(})

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/__init__.py", line 58, in parse
    return grammar.parse(code, **kwargs)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/grammar.py", line 156, in parse
    root_node = p.parse(tokens=tokens)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/python/parser.py", line 79, in parse
    return super().parse(tokens)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 129, in parse
    self._add_token(token)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 186, in _add_token
    self.error_recovery(token)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/python/parser.py", line 140, in error_recovery
    return super().error_recovery(token)
  File "/home/moose/.pyenv/versions/3.10.2/lib/python3.10/site-packages/parso/parser.py", line 152, in error_recovery
    raise ParserSyntaxError('SyntaxError: invalid syntax', error_leaf)
parso.parser.ParserSyntaxError: ('SyntaxError: invalid syntax', <ErrorLeaf: PythonTokenTypes.OP:'}', (1, 15)>)
>>> rf"\{foobar:>3o}"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'foobar' is not defined
>>> foobar = 3
>>> rf"\{foobar:>3o}"
'\\  3'