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ruff/crates/ruff_python_parser
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Dhruv Manilawala 68a8978454
Consider line continuation character for re-lexing (#12008) 
## Summary

This PR fixes a bug where the re-lexing logic didn't consider the line
continuation character being present before the newline character. This
meant that the lexer was being moved back to the newline character which
is actually ignored via `\`.

Considering the following code:
```py
f'middle {'string':\
        'format spec'}

```

The old token stream is:
```
...
Colon 18..19
FStringMiddle 19..29 (flags = F_STRING)
Newline 20..21
Indent 21..29
String 29..42
Rbrace 42..43
...
```

Notice how the ranges are overlapping between the `FStringMiddle` token
and the tokens emitted after moving the lexer backwards.

After this fix, the new token stream which is without moving the lexer
backwards in this scenario:
```
FStringStart 0..2 (flags = F_STRING)
FStringMiddle 2..9 (flags = F_STRING)
Lbrace 9..10
String 10..18
Colon 18..19
FStringMiddle 19..29 (flags = F_STRING)
FStringEnd 29..30 (flags = F_STRING)
Name 30..36
Name 37..41
Unknown 41..44
Newline 44..45
```

fixes: #12004 

## Test Plan

Add test cases and update the snapshots.
2024-06-25 02:13:54 +00:00
..
resources Consider line continuation character for re-lexing (#12008) 2024-06-25 02:13:54 +00:00
src Consider line continuation character for re-lexing (#12008) 2024-06-25 02:13:54 +00:00
tests Consider line continuation character for re-lexing (#12008) 2024-06-25 02:13:54 +00:00
Cargo.toml Remove less used parser dependencies (#11718) 2024-06-03 13:08:24 +00:00
CONTRIBUTING.md Add basic docs for the parser crate (#11199) 2024-04-29 17:08:07 +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.