Use rust-project.json instead of patching Cargo.toml

[ragne]

Preface

I've noticed that to use rust-analyzer with clippy you need to run cargo dev ra-setup, which'll patch existing Cargo.toml for workspace and clippy-lints.
After that it was cumbersome (maybe just for me) to run compile/test because now cargo basically tries to compile parts of the rust.
And of course you need to get rid of those bits before submitting a PR.

Proposal

Nowadays rust-analyzer has a different way to define a project, mostly intended for projects that don't use Cargo. One can write a rust-project.json and point rust-analyzer to that file instead.
Could it be used instead and put into .gitignore for example? I think it should be more convenient than current solution.

I probably can take the ticket on the next week and try to come with PR.
Main questions (assuming approach works):

• Should it replace existing ra-setup or add a feature flag?
• Should it try to locate .vscode settings and specify rust-analyzer.linkedProjects for user?
• Support for any other editors if previous is true?

[dima74]

After that it was cumbersome to run compile/test because now cargo basically tries to compile parts of the rust.

I also faced this problem and fixed it by putting rustc crates under [target.'cfg(NOT_A_PLATFORM)'.dependencies] section

[phansch]

Using the rust-project.json will not be necessary once/if rust-lang/rust#76856 lands and the rustc internals are included in the rustc-dev component.

[flip1995]

rust-lang/rust#76856 landed. Does this mean we can remove the ra_setup command from cargo dev? cc @matthiaskrgr

[matthiaskrgr]

Mhh, it seems that 76856 did not help, RA does not automatically find rustc sources in clippy, at least when I tried.
cc rust-lang/rust-analyzer#3517
I found compiler sources at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/rustc-src/rust/compiler.

We could perhaps use that (and use master toolchain sources) instead of some kind of path to a local repo at least...

[matthiaskrgr]

Hm, right now, ra is broke for me anyway, see https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0/topic/Fixing.20sysroot.20loading

[flip1995]

rust-analyzer works for me. But it doesn't find the rustc source because this isn't implmented in rust-analyzer yet :D Probably needs the same as this:

https://github.com/rust-analyzer/rust-analyzer/blob/96e988fcc3be11acc89dc2c1957bc14e8f39c911/crates/project_model/src/sysroot.rs#L108

[blyxyas]

I think this issue can be closed. cargo dev ra-setup doesn't even exist anymore, #6869 and the solution to Rust Analyzer not finding crates is documented.

{
	"rust-analyzer.rustc.source": "discover",
	"rust-analyzer.linkedProjects": [
        "./Cargo.toml",
        "clippy_dev/Cargo.toml",
        "lintcheck/Cargo.toml",
    ]
}