A process for bringing high-churn-but-beneficial lints to being warn-by-default

Description

There are a few lints in Clippy that, while being imo pretty useful, unfortunately remain in restriction, as enabling them by default would mean a lot of churn for older/larger projects -- some examples being be allow_attributes and redundant_test_prefix.

I guess one way to solve this to make cargo new populate Cargo.toml with x = warns for all such lints, but that could quickly become unwieldy, similarly to how a lot of C/C++ projects are (in my, admittedly small, experience with those) built with a bajillion of -Wxxx flags.

And honestly, it sounds simple enough for the older projects to add a blanket allow for any new warn-by-default lints (and then possibly work on removing all the linted cases to eventually remove the allow, but that's left to each project to decide). Does this break backwards-compat, given that these will be just warnings, not build failures?

But if even that is deemed unpalatable, then it would be nice to find some other solution.

Version

Additional Labels

@rustbot label C-question

Start by reviewing the Clippy documentation for the allow_attributes and redundant_test_prefix lints, then examine how cargo new and Cargo.toml configuration relate to lint defaults. Clarify whether a documented process for moving selected restriction lints to warn-by-default is acceptable and define the criteria and migration outcome for such a change.