repeat-until-convergence

[KDruzhkin]

TL;DR

Some fixes, when applied, create conditions for other fixes.

I would like to have a configuration option to run ruff check --fix until convergence, i.e. until no new changes can be made.

[tool.ruff.lint]
repeat_until_convergence = true

I work in Visual Studio Code with Ruff extension. If the extension behaves differently from command-line ruff check --fix, it should be configurable as well.

An example

Recently I went through a large code base, adding from __future__ import annotations where it missed. This simple change started a cascade of other changes.

This code is flagged with TCH002 ("Move numpy.typing into a type-checking block"):

from __future__ import annotations

from typing import TypeAlias

import numpy.typing as t

ID: TypeAlias = int


def foo(x: t.NDArray) -> int:
    return len(x)

I obediently click Ctrl_+. and select a quick fix.

Now, this code is flagged with I001 ("Import block is unsorted"):

from __future__ import annotations

from typing import TypeAlias, TYPE_CHECKING


if TYPE_CHECKING:
    import numpy.typing as t

ID: TypeAlias = int


def foo(x: t.NDArray) -> int:
    return len(x)

Sometimes the chain is longer than two steps, but I cannot reproduce it now.

An analogy

Phonology and historical linguistics study phonological rules, i.e. regularities of the form "change A to B in context C". At the verty heart of this study is the notion of ordering: one rule can trigger or block another rule:

• https://en.wikipedia.org/wiki/Feeding_order
• https://en.wikipedia.org/wiki/Bleeding_order

Further questions

• Is the order of rules fixed or not? (Is it part of the public API?) If you change this order internally, can it be a breaking change?

• Is it difficult to create a graph of interactions? If rule A can trigger (or block) rule B, I would like to see it in the documentation for the rules.

Keywords

I have searched open issues with: 'recursive' (found #6254), 'iterative' (found #8272), 'fixed point' (found #10058), 'fixpoint', and 'convergence'.

[KDruzhkin]

Sorry, does not belong to ruff itself, but to ruff-vscode.

astral-sh/ruff-vscode#451.