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Summary -- Fixes #20844 by refining the unsupported syntax error check for [PEP 701] f-strings before Python 3.12 to allow backslash escapes and escaped outer quotes in the format spec part of f-strings. These are only disallowed within the f-string expression part on earlier versions. Using the examples from the PR: ```pycon >>> f"{1:\x64}" '1' >>> f"{1:\"d\"}" Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: Invalid format specifier '"d"' for object of type 'int' ``` Note that the second case is a runtime error, but this is actually avoidable if you override `__format__`, so despite being pretty weird, this could actually be a valid use case. ```pycon >>> class C: ... def __format__(*args, **kwargs): return "<C>" ... >>> f"{C():\"d\"}" '<C>' ``` At first I thought narrowing the range we check to exclude the format spec would only work for escapes, but it turns out that cases like `f"{1:""}"` are already covered by an existing `ParseError`, so we can just narrow the range of both our escape and quote checks. Our comment check also seems to be working correctly because it's based on the actual tokens. A case like [this](https://play.ruff.rs/9f1c2ff2-cd8e-4ad7-9f40-56c0a524209f): ```python f"""{1:# }""" ``` doesn't include a comment token, instead the `#` is part of an `InterpolatedStringLiteralElement`. Test Plan -- New inline parser tests [PEP 701]: https://peps.python.org/pep-0701/ |
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Ruff Python Parser
Ruff's Python parser is a hand-written recursive descent parser which can parse Python source code into an Abstract Syntax Tree (AST). It also utilizes the Pratt parsing technique to parse expressions with different precedence.
Try out the parser in the playground.
Python version support
The parser supports the latest Python syntax, which is currently Python 3.12.
It does not throw syntax errors if it encounters a syntax feature that is not
supported by the target-version.
This will be fixed in a future release (see https://github.com/astral-sh/ruff/issues/6591).
Contributing
Refer to the contributing guidelines to get started and GitHub issues with the parser label for issues that need help.