Cargo: unnecessary rebuilds

[brightlandco]

Problem

cargo test causes a rebuild of unchanged files.

Steps

For a reasonably large project with multiple sub-crates etc:

1. cargo test
2. cargo test
3. cargo test

Each time cargo rebuilds files before running tests- major time waste (doesn't happen for small projects).

Possible Solution(s)

Delta checking / dependency system isn't working?

Notes

Output of cargo version:

cargo 1.38.0 (23ef9a4 2019-08-20)

[ehuss]

Can you provide more details or a reproduction? I would look for a misbehaving build script.

You can also run with the CARGO_LOG=cargo::core::compiler::fingerprint=trace environment variable to get some logging information which explains why cargo thinks it needs to be rebuilt.

[ehuss]

I'm going to close this for now. If you can provide more detail, feel free to reopen.