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Brent Westbrook 2baaedda6c
[syntax-errors] Start detecting compile-time syntax errors (#16106) 
## Summary

This PR implements the "greeter" approach for checking the AST for
syntax errors emitted by the CPython compiler. It introduces two main
infrastructural changes to support all of the compile-time errors:
1. Adds a new `semantic_errors` module to the parser crate with public
`SemanticSyntaxChecker` and `SemanticSyntaxError` types
2. Embeds a `SemanticSyntaxChecker` in the `ruff_linter::Checker` for
checking these errors in ruff

As a proof of concept, it also implements detection of two syntax
errors:
1. A reimplementation of
[`late-future-import`](https://docs.astral.sh/ruff/rules/late-future-import/)
(`F404`)
2. Detection of rebound comprehension iteration variables
(https://github.com/astral-sh/ruff/issues/14395)

## Test plan
Existing F404 tests, new inline tests in the `ruff_python_parser` crate,
and a linter CLI test showing an example of the `Message` output.

I also tested in VS Code, where `preview = false` and turning off syntax
errors both disable the new errors:


![image](https://github.com/user-attachments/assets/cf453d95-04f7-484b-8440-cb812f29d45e)

And on the playground, where `preview = false` also disables the errors:


![image](https://github.com/user-attachments/assets/a97570c4-1efa-439f-9d99-a54487dd6064)


Fixes #14395

---------

Co-authored-by: Micha Reiser <micha@reiser.io>
2025-03-21 14:45:25 -04:00
..
resources [syntax-errors] Start detecting compile-time syntax errors (#16106) 2025-03-21 14:45:25 -04:00
src [syntax-errors] Start detecting compile-time syntax errors (#16106) 2025-03-21 14:45:25 -04:00
tests [syntax-errors] Start detecting compile-time syntax errors (#16106) 2025-03-21 14:45:25 -04:00
Cargo.toml Allow passing ParseOptions to inline tests (#16357) 2025-02-27 10:23:15 -05:00
CONTRIBUTING.md py-fuzzer: recommend using uvx rather than uv run to run the fuzzer (#14645) 2024-11-27 22:19:52 +00:00
README.md Add basic docs for the parser crate (#11199) 2024-04-29 17:08:07 +00:00

README.md

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.