ruff/crates/ruff_python_formatter/resources
Dhruv Manilawala 77a72ecd38
Avoid multiline expression if format specifier is present (#11123)
## Summary

This PR fixes the bug where the formatter would format an f-string and
could potentially change the AST.

For a triple-quoted f-string, the element can't be formatted into
multiline if it has a format specifier because otherwise the newline
would be treated as part of the format specifier.

Given the following f-string:
```python
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {
    variable:.3f} ddddddddddddddd eeeeeeee"""
```

The formatter sees that the f-string is already multiline so it assumes
that it can contain line breaks i.e., broken into multiple lines. But,
in this specific case we can't format it as:

```python
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {
    variable:.3f
} ddddddddddddddd eeeeeeee"""
```
                     
Because the format specifier string would become ".3f\n", which is not
the original string (`.3f`).

If the original source code already contained a newline, they'll be
preserved. For example:
```python
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {
    variable:.3f
} ddddddddddddddd eeeeeeee"""
```

The above will be formatted as:
```py
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {variable:.3f
} ddddddddddddddd eeeeeeee"""
```

Note that the newline after `.3f` is part of the format specifier which
needs to be preserved.
The Python version is irrelevant in this case.

fixes: #10040 

## Test Plan

Add some test cases to verify this behavior.
2024-04-26 13:34:38 +00:00
..
test/fixtures Avoid multiline expression if format specifier is present (#11123) 2024-04-26 13:34:38 +00:00