Override the existing cache key

[cornelius-span]

I am trying to create essentially a common cache across multiple branches regardless of lockfile sum. In the documentation it is specified that the 'shared-key' field is:

A cache key that is used instead of the automatic job-based key

however when I specify a 'shared-key' the lock files and other parameters are still used in the cache key which results in many copies of the cache (which is quite large). I am wondering:

a) is it possible to fully specify the cache key
b) what is the preferred method for reusing a single cache across multiple branches with modifications.

I understand that this will probably slow down build times slightly because the incremental build will not be a perfect fit however it is preferable than rebuilding from scratch (and creating a ~2gb cache) each time a new branch is pushed

[NobodyXu]

however it is preferable than rebuilding from scratch (and creating a ~2gb cache) each time a new branch is pushed

GitHub Action cache can be shared between branches.

If a branch is created from main, then it can reuse cache from main.

If a branch is created from branch dev, which is then created from main, then you can reuse cache from dev and main.

[cornelius-span]

I understand but this is based on the cache key. Currently when I specify a "shared-key" or "key" ex:

with:
workspaces: "${{ env.DIRS }}"
shared-key: "${{ matrix.ci_node_index }}-Rust"

the cache key ends up looking something like:
v0-rust-0-Rust-593f00b5-f42bcd39

which means that it is still using the hash of the cargo lock files which I dont want to do (I want to just have a common cache that is only updated by pushes to main but is always pulled in on all feature branches).

I want the cache key to just be something like:
1-Rust

[KiraCoding]

I require this too, I want my pull requests to re-use the main branch cache, but it always creates a new branch based cache instead of re-using/updating the main branch cache, either I misunderstood how this whole thing works or it's simply not implemented?

[NobodyXu]

@KiraCoding If you modify cargo toolchain, cargo/rust envs, Cargo.toml/Cargo.lock, then rust-cache would restore cache from main and upload a new one to the branch.

GHA has cache protection rules that forbidden PR/branches GHA run cache to be reused in main, though they can always reuse cache they are branched from.

[NobodyXu]

@cornelius-span That's probably a bug then