cargo (original) (raw)

Problem

Context: I have a project that is a workspace that contains multiple library crates that are outputting cdylib types.

Bug/Expectation: When I build in the root of the workspace, I would expect running cargo build -p <crate> to be a noop as the workspace cargo build should have built all of it. If running cargo build -p <crate> outputs to a different cache, then I would expect that the cargo build and cargo build -p to not affect each other at all. Instead, whenever I build cargo build, it invalidates the individual cargo build of the crate's dependencies and forces a rebuild...

Steps

https://github.com/Kevin-Reactor/Fingerprint-Repro

Here is a public repo of a minimal reproduction of the issue.

Step 1: Download the repo
Step 2: run cargo build in the root directory
Step 3: run cargo build -p test_2
Step 4: Alternate between running cargo build and CARGO_LOG=cargo::core::compiler::fingerprint=info cargo build -p test_2 and you can see it complain that the fingerprint for serde_yaml has changed

Possible Solution(s)

No response

Notes

I have tested a few configurations, this only seems to happen when the libraries output cdylib, and only happens when there are two crates (i.e. a workspace with only one crate doesn't have this issue)

It also seems to happen with specific crates. quiche and serde_yaml specifically but I have no idea why.

I know that there's an issue with the features of the crates potentially being different between building in root and building with -p, but it makes no sense that this configuration doesn't require rebuilds with lib instead of cdylib and that they don't have any shared features...

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