Src file mapping not working properly with trybuild and proc-macro workspace member

[teoxoy]

When running integration tests (via trybuild) for a proc-macro crate that is a workspace member, the following warning is output:

error: dep/dep/src/lib.rs: No such file or directory
warning: The file 'dep/dep/src/lib.rs' isn't covered.

cmd run:

cargo llvm-cov --workspace --html

The report ends up showing 2 entries for the same src file as seen below

You can find a small reproducible sample here: test.tar.gz

This seems to be happening even if trybuild::TestCases::new() is the only thing in the test fn (no calls to pass or compile_fail).
It also seems to work fine if the crate is a normal lib instead of a proc-macro lib.

I wasn't sure if this is an issue with cargo-llvm-cov or trybuild but having tried tarpaulin with success (same setup), I thought it might be an issue with cargo-llvm-cov.

[taiki-e]

Thanks for the report!

This appears to be a bug in rustc's --remap-path-prefix. If I disable it, it works correctly (#141).

[teoxoy]

I tested the PR and it seems to solve the issue.
Thanks for the quick response and fix!

Do you have any concerns with the change in the PR?
Also, should we report the bug upstream?

[taiki-e]

The problem I am currently aware of is that our test suite does not work well because the reports show absolute paths.

cargo-llvm-cov/tests/fixtures/coverage-reports/no_test/link_dead_code.txt

Line 1 in 20d5da7

/private/var/folders/r3/hm536h9x0nj5zfh1qtyt7hth0000gn/T/.tmpsGNoB8/src/lib.rs:

Another concern is that this may be a problem when merging coverage between different platforms. (I have not looked into this yet.)

So, for now, I'm starting to think it is reasonable to provide an option to disable --remap-path-prefix.

[taiki-e]

According to ruifengx/rowantlr#3, this seems to be a regression introduced around 2021-11-30.

[teoxoy]

Maybe something to do with rust-lang/rust#83846 (merged on 2021-11-11)?

[taiki-e]

Published 0.3.0 which includes the fix for this.