compiletest: `./x test <filter>` is a substring match

[jieyouxu]

This is very non-intuitive...

I tried on native x86_64-pc-windows-msvc:

./x test tests/run-make/exp/ --stage 1

This showed me 8 tests were ignored (incl. a local tests/run-make/exp/ test I added for testing) even though I would've expected an exact match for only the local test I added:

[23:37] Joe:rust (return-adjustment-target) | ls -d tests/run-make/*exp*
tests/run-make/export-executable-symbols/             tests/run-make/share-generics-export-again/
tests/run-make/extern-fn-explicit-align/              tests/run-make/wasm-export-all-symbols/
tests/run-make/mingw-export-call-convention/          tests/run-make/wasm-symbols-not-exported/
tests/run-make/rustdoc-scrape-examples-invalid-expr/

I almost never want this substring match behavior, at least not unless I explicitly write some kind of --test-name="exp", for example.

I suspect this is some behavior related to the test name constructed by compiletest, which is fed to libtest which probably handles the test filtering... Ah, it might be the test name constructed from the test path...

[jieyouxu]

I have not investigated if this is true for run-make tests only, or if this is a generic compiletetst behavior.

[jieyouxu]

This behavior is indeed applicable generally, it seems like. E.g. necessary and sufficient condition to reproduce:

tests/
    ui/
        unknown/ # <- just that dir must exist
        unknown-1.rs
        unknown-2.rs
        meow-unknown-bar.rs

A folder must exists that shares the same "prefix" name, e.g. unknown/, and some other tests must contain unknown. Writing ./x test tests/ui/unknown/ will run all of these tests.

There's a bootstrap check that asserts the filter must correspond to an existing directory or file, but that's actually kind of misleading...

[jieyouxu]

Note that the combined effect of compiletest handling + underlying libtest means that ./x test <test_folder_path> -- -- --exact does what I expect ./x test <test_folder_path> to do, but I find this very confusing...