test: remove the use of CARGO_RUSTC_CURRENT_DIR

[weihanglo]

What does this PR try to resolve?

The environment variable has been removed in #14799.
Switch to plain old CARGO_MANIFEST_DIR
because snapbox's current_rs favors furthest Cargo.toml,
blocking tests running in rust-lang/rust as a submodule.

See also build failures in rust-lang/rust#133533

How should we test and review this PR?

Pull this change into rust-lang/rust and run

./x.py test src/tools/cargo

[rustbot]

r? @epage

rustbot has assigned @epage.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[epage]

We likely still want this for snapbox which reads CARGO_RUSTC_CURRENT_DIR

[weihanglo]

I've tested SNAPSHOTS=overwrite to update inline snapshots for some tests in

• tests/build-std/main.rs
• tests/testsuite/rename_deps.rs
• crates/cargo-util-schemas/src/manifest/rust_version.rs

And they are all working.

I assume we don't really need that except for people working on Cargo from rust-lang/rust repo. I can keep it there if this is what we want to support.

[epage]

Snapbox also uses CARGO_RUSTC_CURRENT_DIR. However, that is only on test failure when SNAPSHOTS=overwrite is specified which is why it isn't a problem.

[epage]

Do we know why this doesn't work for bootstrap but it works for everything else? Are they running our tests outside of our repo, making it so the config isn't loaded? Could that change?

[weihanglo]

Do we know why this doesn't work for bootstrap but it works for everything else? Are they running our tests outside of our repo, making it so the config isn't loaded? Could that change?

I believe that is because bootstrap invokes cargo with --manifest-path without cd to the package root.

[bors]

☔ The latest upstream changes (presumably 3908f64) made this pull request unmergeable. Please resolve the merge conflicts.

[weihanglo]

[…] Are they running our tests outside of our repo, making it so the config isn't loaded? Could that change?

It might be possible to change, but that requires bootstrap team's involvement. I would suggest we unblock this first, and then discuss with other folks for any further refactors.

[weihanglo]

Suggest a patch to that PR: rust-lang/rust#133533 (comment).

[weihanglo]

Close as this patch works.