Bug: default store directory does not respect CARGO_TARGET_DIR

[tgross35]

Description of the issue

Description:

Nextest always tries to create the store directory at the workspace root, which fails if the workspace is read-only.

Steps to reproduce:

1. Go to any existing project, ensure the target directory is clean (or at least target/nextest does not exist)
2. Launch a Docker container that mounts the current workspace as read only, and sets CARGO_TARGET_DIR. : docker run --rm -e CARGO_TARGET_DIR=/target -v "$(pwd):/checkout:ro" -it rust bash
3. Install nextest: cargo install cargo-nextest
4. cd /checkout
5. Try running tests normally: cargo test. This should work
6. Try running tests via nextest: cargo nextest run. This fails with something like:

error: failed to create store dir at `/checkout/target/nextest/default`

Caused by:
  Read-only file system (os error 30)

Expected outcome

By default, rather than using a path relative to the workspace root, nextest should create its store directory within CARGO_TARGET_DIR if it is set.

Actual result

Unable to create the file (see above)

Nextest version

cargo-nextest 0.9.87 (fee71ad7b 2024-12-17)
release: 0.9.87
commit-hash: fee71ad7ba08be06519cf9eeb495c6fce0a2e888
commit-date: 2024-12-17
host: aarch64-unknown-linux-gnu

Additional context

No response

[sunshowers]

Thanks -- yeah, this has been a problem for a while. I'd definitely like to change the default at some point, but that would have to be a carefully-managed behavior change. I think for now we should let you set the target directory to be the same as CARGO_TARGET_DIR.

[tgross35]

Would some form of environment interpolation in config be possible? Maybe the default could change to be store.dir = "${CARGO_TARGET_DIR:-target}/nextest" which would probably be correct in most cases.

[sunshowers]

Yeah -- though in this other case we decided to let you say relative-to = "target", which we should probably be consistent with.

https://nexte.st/docs/ci-features/archiving/#adding-extra-files-to-an-archive

So you'd say

store.dir = { path = "nextest", relative-to = "target" }

and we'd eventually make this the default.