Set environment variables specified via `cargo::rustc-env` in the build script

[chrjabs]

As discussed in #1787, cargo test does this, so nextest should too.

I added warnings in case the build script output file is not found, this should usually have been created when cargo executes the build script. I also decided to package the build script output file in the same step as the build script output directory. Let me know if you prefer creating a separate step for this.

I tried to approach this with minimal changes, maybe it would be nicer to store the path to the $OUT_DIR parent, so that getting the path of the output file is a tad simpler, but that would have required me touching more code. Let me know if you have suggestions for implementing any of this differently.

Side note: trying to run tests with cargo run -p cargo-nextest -- nextest run --all-features failed with tracing complaining that it failed to set a global subscriber since one is already set, so I ran tests without the --all-features flag.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 87.87879% with 8 lines in your changes missing coverage. Please review.

Project coverage is 79.92%. Comparing base (93fcd9e) to head (3a5625e). Report is 21 commits behind head on main.

Files with missing lines	Patch %	Lines
nextest-runner/src/test_command.rs	88.23%	6 Missing :warning:
nextest-runner/src/reuse_build/archiver.rs	85.71%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1798      +/-   ##
==========================================
+ Coverage   79.91%   79.92%   +0.01%     
==========================================
  Files          80       80              
  Lines       20179    20244      +65     
==========================================
+ Hits        16126    16180      +54     
- Misses       4053     4064      +11     

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[chrjabs]

Ah, I didn't realize you're testing against 1.75, which doesn't support the new cargo:: syntax yet. Any ideas for how to circumvent this? I could make the with-build-script test crate depend on rustversion to only include the new syntax test conditionally.

[chrjabs]

I changed the test to be dependent on the rustversion crate now, but I kept it a separate commit for now, since this requires a new dependency for the testing fixtures, and I'm not sure if this is fine. If yes, the commits should be squashed, otherwise we'll need another fix.

[sunshowers]

Thanks! Can this use a very simple version check, similar to:

https://github.com/camino-rs/camino/blob/467b33692ac2224f6ccfb6b4e96d7dfe2ea09ec7/build.rs#L32-L34

I don't think it's necessary to pull down a dependency here.

[chrjabs]

Thanks for the pointer of where to look for how to do this. I agree that this is definitely cleaner this way.

[chrjabs]

Now also added documentation, where I noted that cargo actually discourages using these variables at runtime. I hadn't noticed that before.

[sunshowers]

Side note: trying to run tests with cargo run -p cargo-nextest -- nextest run --all-features failed with tracing complaining that it failed to set a global subscriber since one is already set, so I ran tests without the --all-features flag.

Ah good catch, I'll try and fix this.

[sunshowers]

Released this as part of cargo-nextest 0.9.82. Thanks again!

Ah good catch, I'll try and fix this.

Fixed in https://github.com/nextest-rs/nextest/commit/11623d5ce06fd63ff3803499e594400876bac502.