RLS always starts full analysis after VS Code is restarted

[ancwrd1]

After updating to a recent nightly toolchain RLS always performs full project analysis each time the VS Code (with Rust plugin) is restarted, instead of using the cached data from target directory like in the previous builds. It causes massive CPU load even on small projects.

There is rls.toml file in the root directory with "build_lib=true" setting.

[nrc]

This is a regresssion and feels like it could be a regression in Cargo. I'll try to reproduce.

cc @alexcrichton - any obvious changes recently that might cause this?

[nrc]

full project analysis

To clarify, this means analysis of all crates or just the primary crate? The former is bad, the latter is expected.

[ancwrd1]

All crates, like doing a full rebuild.

[rookwood101]

I'm also experiencing this problem, using RLS is basically impossible on my laptop; it gets so hot.

[Xanewok]

After setting RUST_LOG to cargo::ops::cargo_rustc::fingerprint it can be observed that the rebuilding is caused by RUSTFLAGS mismatch, somehow caused by dedup_flags. Temporarily commenting that out seems to temporarily get rid of the problem. From what i understand the flags still should consistently remain the same, even after deduping, not causing a problem. Nevertheless, this needs some more investigating.

Is there an easy temporary fix available for this somehow? This bug is basically a show stopper and has made me stop using RLS. Even on a very fast workstation, this means it can take several minutes before RLS becomes responsive after opening the project.

[nrc]

@Xanewok interesting, that def seems like a bug in dedup_flags - it should be consistent. Maybe should use something ordered rather than a HashMap? (BTreeMap or something)

[nrc]

This is still happening for me.

[Xanewok]

@nrc May not be related, but if you're using logging in rls_vscode, remember that with every file addition/modification/deletion inside project root (e.g. rls*.log files) project fingerprint stops matching since last compilation and (only) it will be rebuilt.

[nrc]

So, on investigation it seems that multiple builds were getting kicked off and post-processing is taking too long, but that we're no longer doing a full rebuild.