compile-test tests fail to run when using a custom `build-dir`

[jakubadamw]

Description

I have the following in my ~/.cargo/config.toml:

[build]
build-dir = "{cargo-cache-home}/build-artifacts/{workspace-path-hash}"

and that means intermediate artifacts (including final artifacts of dependencies) get written to ~/.cargo/build-artifacts rather than the target directory (./target/{debug,release}/{build,deps,…}).

When I try to run Clippy's compile-test tests, the harness will fail with:

➜  rust-clippy git:(master) cargo uitest -- default_trait_access
   Compiling clippy v0.1.95 ([…]/Projects/Rust/rust-clippy)
    Finished `test` profile [unoptimized + debuginfo] target(s) in 1.40s
     Running tests/compile-test.rs ([…]/.cargo/build-artifacts/17/4ed237e20fa79c/debug/deps/compile_test-fdede6d307b30bd0)

thread 'main' (10541131) panicked at tests/compile-test.rs:250:6:
called `Result::unwrap()` on an `Err` value: failed to parse rustc version info: "RUSTC_ICE"="0" "CLIPPY_CONF_DIR"="tests" /[…]/.cargo/build-artifacts/17/4ed237e20fa79c/debug/clippy-driver "--error-format=json" "--emit=metadata" "-Aunused" "-Ainternal_features" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Dwarnings" "--out-dir" OUT_DIR

Caused by:
   0: could not execute command: No such file or directory (os error 2)
   1: No such file or directory (os error 2)

The problem is here where it is assumed that clippy-driver (a final build artifact) is located in the parent directory of compile_test-… (an intermediate artifact), and that doesn't hold when build-dir is configured independently from target-dir.

Version

0f4f81df13a18212e1b3b578ccfc8d055ad120be, master as of 13 Feb 2026.

Additional Labels

No response

[samueltardieu]

PR #16568 may be reverted, reopening. See links in PR.