Insert newline after nested function or class statements

[konstin]

Summary Insert a newline after nested function and class definitions, unless there is a trailing own line comment.

We need to e.g. format

if platform.system() == "Linux":
    if sys.version > (3, 10):
        def f():
            print("old")
    else:
        def f():
            print("new")
    f()

as

if platform.system() == "Linux":
    if sys.version > (3, 10):

        def f():
            print("old")

    else:

        def f():
            print("new")

    f()

even though f() is directly preceded by an if statement, not a function or class definition. See the comments and fixtures for trailing own line comment handling.

Test Plan I checked that the new content of newlines.py matches black's formatting.

[konstin]

Current dependencies on/for this PR:

• main
  • PR Insert newline after nested function or class statements #7946 👈
    • PR Move {AnyNodeRef, AstNode} to ruff_python_ast crate root #8011

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[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.

[MichaReiser]

Leaving to @charliermarsh for the final review as his more familiar with the empty line rules than I

[MichaReiser]

Is any here correct? Shouldn't we only test this for the last node:

if True:
	if False:
		def double(s):
			...
	#trailing comment, if gets excluded by the `filter` and the `any` will be true.

[charliermarsh]

I think successors will short circuit as soon as it sees a node with a trailing comment, so the any would be false.

[charliermarsh]

But I may be misunderstanding, it's a bit confusing.

[konstin]

Tried to make the code clearer, it's a bit complex with the recursive logic unfortunately

[charliermarsh]

What was the motivation for making this an associated function?

[charliermarsh]

(Not necessarily disagreeing, just looking to understand.)

[konstin]

I needed to share it outside of placement where it used to be private helper function and then it seemed natural that "what is the last child of this node" is a property of node