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Brent Westbrook 38c074e67d
Catch syntax errors in nested interpolations before Python 3.12 (#20949) 
Summary
--

This PR fixes the issue I added in #20867 and noticed in #20930. Cases
like this
cause an error on any Python version:

```py
f"{1:""}"
```

which gave me a false sense of security before. Cases like this are
still
invalid only before 3.12 and weren't flagged after the changes in
#20867:

```py
f'{1: abcd "{'aa'}" }'
           # ^  reused quote
f'{1: abcd "{"\n"}" }'
            # ^  backslash
```

I didn't recognize these as nested interpolations that also need to be
checked
for invalid expressions, so filtering out the whole format spec wasn't
quite
right. And `elements.interpolations()` only iterates over the outermost 
interpolations, not the nested ones.

There's basically no code change in this PR, I just moved the existing
check
from `parse_interpolated_string`, which parses the entire string, to
`parse_interpolated_element`. This kind of seems more natural anyway and
avoids
having to try to recursively visit nested elements after the fact in
`parse_interpolated_string`. So viewing the diff with something like

```
git diff --color-moved --ignore-space-change --color-moved-ws=allow-indentation-change main
```

should make this more clear.

Test Plan
--

New tests
 		2025-10-20 09:03:13 -04:00
..
resources Catch syntax errors in nested interpolations before Python 3.12 (#20949) 2025-10-20 09:03:13 -04:00
src Catch syntax errors in nested interpolations before Python 3.12 (#20949) 2025-10-20 09:03:13 -04:00
tests Catch syntax errors in nested interpolations before Python 3.12 (#20949) 2025-10-20 09:03:13 -04:00
CONTRIBUTING.md Update usage instructions and lockfile for py-fuzzer script (#20940) 2025-10-17 15:57:17 +01:00
Cargo.toml [ty] Add environment variable to dump Salsa memory usage stats (#18928) 2025-06-26 21:27:51 +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.