Rust analyzer creates `target` directory at project root when using non-Cargo based project

[csmulhern]

I'm using the Bazel build system. The rules_rust project (https://github.com/bazelbuild/rules_rust) adds build rules to Bazel that allow generation of a rust-project.json file to support usage of rust-analyzer with a Non-Cargo Based Project (https://rust-analyzer.github.io/book/non_cargo_based_projects.html). This looks something like:

{
  "sysroot": "/private/var/tmp/_bazel_cameron/f5a6fe93ded5fb771eddb255ace4ff75/external/rules_rust++rust+rust_analyzer_1.88.0_tools",
  "sysroot_src": "/private/var/tmp/_bazel_cameron/f5a6fe93ded5fb771eddb255ace4ff75/external/rules_rust++rust+rust_analyzer_1.88.0_tools/lib/rustlib/src/library",
  "crates": [...]
}

As of a recent release, this causes rust-analyzer to repeatedly generate a lockfile (target/rust-analyzer-metadata/sysroot/Cargo.lock) in the project root directory. It'd be nice to not have this happen, given that we're not using Cargo to begin with, and I'd prefer to not pollute my project directory vs e.g. having to add this path to gitignore.

rust-analyzer version: 2025-06-23

rustc version: 1.88

editor or extension: Zed

relevant settings: ^

code snippet to reproduce: see the config above

[Veykril]

Right ... rust-project.json project's don't have a concept of an out/target dir, so I guess we either need to allocate a temp directory or not use the lock file path redirect

#20018 is the PR that introduced this behavior

[ia0]

I don't think it's only non-Cargo based projects. I have a mono-repo with many Cargo packages (without Cargo workspace because those crates are not part of the same project) with a top-level .cargo/config.toml that says build.target-dir = "target" such that all packages uses the same target directory to factorize build artifacts. Until today (when I updated to the latest nightly) rust-analyzer was respecting the .cargo/config.toml configuration. Now it doesn't.

[Veykril]

Hmm, it not respecting .cargo/config.toml for the target directory should be fixed in the latest nightly.

[ia0]

Hmm, it not respecting .cargo/config.toml for the target directory should be fixed in the latest nightly.

Thanks! Good to know. I'll try again on Monday. Today I get rustc 1.90.0-nightly (b03b3a7ec 2025-06-26) with rustup update and it has the issue.

[ia0]

I confirm the issue. I've created #20133 because I don't think it's the same issue as this one.