compiletest: changes in compiletest does not trigger test rerun

[vakaras]

If I modify a file in the rustc source code (src/librustc_c*), ./x.py test is smart enough to rerun all tests. However, if I modify something in src/tools/compiletest, then ./x.py test still ignores the tests that completed successfully in the previous run.

Steps to reproduce:

1. Run tests:

git clone git@github.com:rust-lang/rust.git
./x.py test

2. Modify compiletest. For example, replace the expected_output_path function in runtest.rs with:

    fn expected_output_path(&self, _kind: &str) -> PathBuf {
        panic!();
    }

3. Run tests again:

./x.py test

Expected output: some tests fail.

Actual output:

Build completed successfully in 0:13:13

[vakaras]

I would be interested in fixing this issue myself if someone could give me some guidance on how to do that. The main thing that I do not understand is how ./x.py test understands that rustc was changed. It seems that it does not use build/x86_64-unknown-linux-gnu/test/ui/*/stamp files for this because they include only the hash of the configuration options which do not include rustc version.

cc @Mark-Simulacrum

[nagisa]

The most likely culprit (that ignores the test files) is fn up_to_date in compiletest::main module. It is called from compiletest::main::make_test and will set the ignore flag for the test depending on its output.

[nagisa]

That being said, I find it hard to see how to adjust compiletest itself to take the dependencies into account. rustbuild should probably have some sort of dependency edge and delete the stamp files if/when stuff like compiletest changes.

[vakaras]

Compiletest source code has only 9 files. Would it be acceptable to check that their timestamps are newer than the timestamp of the stamp file?

PR: https://github.com/rust-lang/rust/pull/56680/files