CI cache not including installed Cargo tools?

[joshlf]

Our generate_cache CI job, which is a dependency of the main build_test job, runs cargo install cargo-nextest. However, in this run, we can see that it's getting re-installed in build_test. This likely means that binaries installed via cargo install are not getting cached.

[sl4m]

Is it possible it's due to the cargo clean call? I see the job you linked matches the target specified here: https://github.com/google/zerocopy/blob/889ac1bc2f38b1ccf338a1bf12f222102b338bc0/.github/workflows/ci.yml#L249C23-L256.

Never mind, it should not affect cargo dependencies.

Note: Saw this issue from This Week in Rust

[joshlf]

Credit to @sl4m for figuring out that this was actually a red herring (#1375 (comment)):

Amazing, thank you for fixing this! I'm not sure I understand why this fix works, though?

Ok, I think I know what's really going on. My change worked in my fork because I did not have existing caches.

I believe cargo-nextest was recently introduced in #1307? If so, it may be a result of an old cache. A new cache is created only if Cargo.toml changes (see here) and since GitHub Actions cache are immutable, it did not preserve the cargo-nextest installation.

Cargo.toml has since been updated via google-pr-creation bot, so the caches should now have cargo-nextest.

I checked a recent build and it looks like it's ignoring the cargo-nextest installation as expected:

Running Miri tests with 8 threads
    Updating crates.io index
     Ignored package `cargo-nextest v0.9.72` is already installed, use --force to override
Preparing a sysroot for Miri (target: aarch64-unknown-linux-gnu)... done

I think I will close this PR if you agree and you can probably close #1312.