`cargo-gpu` doesn't recompile things when `rust-gpu` dependency changes

[nazar-pc]

I was just testing things and noticed an interesting, both expected and unexpected gotcha: changing rust-gpu dependency doesn't result in shader recompilation when cargo-gpu doesn't change.

I use cargo-gpu-install specifically in build.rs and do not have rust-gpu in build dependencies. So while cargo-gpu reads the version/revision of rust-gpu to decide what backend version to use, changing rust-gpu doesn't have any impact on anything that would result in build.rs being recompiled, as such shader is still built with the old version.

One solution might be to include the Cargo.toml of both the crate and probably the workspace root (if any) too in cargo::rerun-if-changed, though it will also result in too many unnecessary recompilations, so it is not perfect.

I do not have a great solution, but wanted to raise this as a concern that might be quite confusing to others and probably worth fixing.

[Firestar99]

I assume with updating rust-gpu you actually mean changing the spirv-std rev.

Yea a cargo::rerun-if-changed would do it, though I'd give it the Cargo.lock instead to also notice automated upgrades by cargo update.

Though, I'll delay fixing this issue until cargo-gpu is merged into rust-gpu.