A minimal code snippet that reproduces the bug.

File name: format_ruff.py

Before ruff:

class MyClass:
    def __add__(self, other: int) -> int: ...

After ruff:

class MyClass:
    def __add__(self, other: int) -> int:
        ...

The command you invoked

ruff format format_ruff.py 

Note: in real-life scenario, one might have installed the Ruff extension on VSCode, opened a file with many stubs like in the minimal code snippet, and see them all formatted, introducing unwanted code change, which can be annoying for version control.

This might also slow down ruff adoption in existing large code bases where the case mentioned above happens a lot.

The current Ruff settings

No overriden settings. I ran a pip install ruff then ran the command above

The current Ruff version

ruff --version
ruff 0.2.2

What I would like

A way to opt-out of de-inlining the Ellipsis (...) in stubs. I have searched in documentation without finding such an option. I browsed the following issues (in Links section).

An option could be:

[tool.ruff.format]
keep-single-line-ellipsis = true

Links

Related Issues:

• Formatter: Ellipses in stub files get formatted on a single line #5822 -> It seems the solution only applied to .pyi files, not .py ; I would like the option to be activable for all types of files.
• Allow reduced number of blank lines for dummy implementations psf/black#1797 (referred to in the issue above)

Related PRs:

• Format function and class definitions into a single line if its body is an ellipsis #6592 (exposes the same situation described in this issue! it seems to only apply to .pyi files, but maybe it could be generalized to .py?)
• Use one line between top-level items if formatting a stub file #6501

Thanks!