Upcoming Ubuntu 24.04 runner may not have Clippy pre-installed

[laniakea64]

In #78 / 53459ce we removed the "Install Rust Toolchain Components" step, because it's redundant in the current CI runner image. But according to documentation of upcoming Ubuntu 24.04 runner and actions/runner-images#9848 , looks like Clippy will no longer be pre-installed in our CI when that runner image becomes ubuntu-latest. Which actions/runner-images#9848 (comment) suggests will likely happen sometime next month.

We need to either reinstate use of rustup for Clippy or temporarily pin our CI to ubuntu-22.04.

[laniakea64]

temporarily pin our CI to ubuntu-22.04.

I'm inclined to go this route:

1. Clippy is far from the only software listed as "Removed from the Ubuntu 24.04 image due to maintenance reasons." With that much software removed for that same reason, it's not immediately clear how many of these removals are expected to be permanent. Maybe wise to delay the switch to Ubuntu 24.04 to see if Clippy might be reinstated later?

2. Switching on our own schedule means we can be sure to adapt to changes at the time of switching and avoid a period of broken CI.

3. Ubuntu 22.04 has Vim 8.2.3995 while Ubuntu 24.04 has Vim 9.1.0016. 8.2.3995 is closer to our minimum supported Vim version, so CI having that version makes it more likely to catch issues.

[laniakea64]

Went ahead with pinning CI to ubuntu-22.04 today to get rid of the urgency.

@NoahTheDuke Anything else to consider/address here, or close this?

[laniakea64]

Ubuntu 24.04 has now been ubuntu-latest for some time, and Clippy is still not listed as included.

From https://github.com/actions/runner-images?tab=readme-ov-file#ga -

we only support the latest 2 versions of an OS.

The OS being Ubuntu LTS, Ubuntu 22.04 will be in "latest 2 versions" until sometime in April 2026. I would be inclined to keep CI on Ubuntu 22.04 for now, and deal with longer-term action in early 2026.