ENH copyright-notice: check in the first 4096 bytes instead of 1024

[adrinjalali]

Summary

related to #5306

The check right now only checks in the first 1024 bytes, and that's really not enough when there's a docstring at the beginning of a file.

A more proper fix might be needed, which might be more complex (and I don't have the rust skills to implement that). But this temporary "fix" might enable more users to use this.

Context: We want to use this rule in https://github.com/scikit-learn/scikit-learn/ and we got blocked because of this hardcoded rule (which TBH took us quite a while to figure out why it was failing since it's not documented).

Test Plan

This is already kinda tested, modified the test for the new byte number.

[zanieb]

Seems okay to me. Thanks for contributing! cc @MichaReiser

[MichaReiser]

Looks okay, although I'm not sure why the limit even exists. The only performance issue that I can see is if the regex uses a wildcard at the start. Any regex without a wildcard at the start should end by just testing a few characters.

[MichaReiser]

Okay it seems that the somewhat arbitrary limit is coming from the original lint rule. I think the limit there makes sense because the rule actually reads the file. The situation for ruff is different because we already have the file in memory.

Anyway, thanks for contributing!

[zanieb]

I'm not sure either cc @BurntSushi

Not a lot of context in the original implementation discussion at #4701

[BurntSushi]

Here's the regex:

ruff/crates/ruff_linter/src/rules/flake8_copyright/settings.rs

Line 18 in 2e7c345

Lazy::new(|| Regex::new(r"(?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*").unwrap());

Specifically:

(?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*

And the search is using Regex::find, which is an unanchored search. So the regex behaves as if there is a (?s:.)*? at the beginning. So putting a limit on how much is searched seems sensible if you only expect it to be near the beginning of file and it's plausible that this could be used to search very large files. I doubt 4096 and 1024 will make much of a difference, so this change seems okay.