Decorated classes below functions aren't separated with blank lines in `.pyi` files

[bzoracler]

Summary

In a stub.pyi, I expect a blank line before a class (including its decorators) when it's defined below a function.

Before formatting:

def hello(): ...

@lambda _, /: _
class A: ...

After formatting:

def hello(): ...
@lambda _, /: _
class A: ...

For reference, the blank line is added by the formatter when the class sits below other statements, like imports, assignments, and other classes.

(I couldn't provide a ruff playground link because I couldn't figure out how to make it format a source file like it would do for stubs. Does such an option in the playground exist?)

---

See psf/black#4256 for reference - the missing blank line isn't intentional, but fixing it in black is apparently not trivial. Is it also not trivial in ruff?

Version

ruff 0.12.0

[MichaReiser]

That makes sense to me. I think that should be fairly easy to change. It might be as easy as removing

ruff/crates/ruff_python_formatter/src/statement/suite.rs

Lines 693 to 706 in 9ae698f

	// Black for some reasons accepts decorators in place of empty lines
	// ```python
	// def _count1(): ...
	// @final
	// class LockType1: ...
	//
	// def _count2(): ...
	//
	// class LockType2: ...
	// ```
	let class_decorator_instead_of_empty_line = preceding.is_function_def_stmt()
	&& following
	.as_class_def_stmt()
	.is_some_and(|class| !class.decorator_list.is_empty());

We would need to gate the change behind preview mode because we can only release it as part of the next minor. See https://github.com/astral-sh/ruff/blob/1aad180aae84cd5d12d5a47c879183f559c871ed/crates/ruff_python_formatter/src/preview.rs#L1-L0 for a few exmaples on how to do that