rust: suggest correct dependency when found in Cargo.lock

[pbo-linaro]

As we refer to crates using API version instead of plain version, it can be confusing to user which is left with a simple "Dependency X not found".

Thus, when we detect that a rust dependency is missing, and is not available using a wrap file, if we find something compatible using Cargo.lock import, we just list the correct dependencies names.

[pbo-linaro]

@xclaesse Followup for conversation on https://github.com/mesonbuild/meson/pull/12945

[pbo-linaro]

fixed extra parentheses on the if.

[pbo-linaro]

Report error only if dependency is required.

[pbo-linaro]

fixed lint issues

[pbo-linaro]

@eli-schwartz How can we indicate to meson test infra that the test is supposed to fail?

[pbo-linaro]

More idiomatic python.

[pbo-linaro]

Use rsplit to extract crate name + update test to have crate with - in the name.

[pbo-linaro]

Thanks for your recommendations @dnicolodi @eli-schwartz. I'm still looking for a way to indicate the test is supposed to fail. If you have suggestion, I would be happy to implement it to fix CI.

[pbo-linaro]

Found how to implement a "failing" test, and rebased on top of master.

[pbo-linaro]

Test failure does not seem related to this patch (lto issue on cygwin).

[pbo-linaro]

Polite ping after two weeks. Review comments have been addressed so far. I still think this error message can be useful for people looking for integrating rust code with meson.

[pbo-linaro]

I'm closing this PR for now. If someone is interested to work on this, feel free to reuse the code presented here.