./x.py test does not rebuild properly

[Aurel300]

This is a minor issue, but if I do the following steps:

1. Start with a working build of prusti, passes tests with ./x.py test --all.
2. Make a change in the codebase, in my case in prusti-specs/src/specifications/preparser.rs
3. Run the tests again with ./x.py test --all.

The last step seems to build some things (including prusti-specs), but after the build is complete and the tests run, they fail with can't find crate for prusti_contracts_internal which prusti_contracts depends on. If I do a proper rebuild ./x.py build --all, and then test again, it's fine.

Maybe there is something wrong with the crate dependencies?

[fpoli]

What happens is that prusti-test uses the binaries of prusti-launch and prusti, but there is no cargo dependency between them because there is no code dependency. (In the old Makefile there was a cargo build before each cargo test to fix this).

I wonder what happens if we declare a dependency without actually using it. Maybe it's enough to make cargo recompile the dependencies (prusti, prusti-launch...) when ./x.py test --all is executed.

[fpoli]

Relevant cargo issue: rust-lang/cargo#4316

[fpoli]

Pending on rust-lang/cargo#9096