Support #[ignore] attribute in defmt_test

[justahero]

This PR adds support for the #[ignore] attribute in defmt_test to solve #390. Similar to the ignore attribute, tests can be annotated with the attribute to ignore particular tests.

• use trybuild crate to check multiple conditions with the proc macro

Note the message is different from the suggestion in #390 and should be revised accordingly if needed

[japaric]

The implementation looks good to me. Thanks for adding the UI tests. Left some comments inline.

Note the message is different from the suggestion in #390 and should be revised accordingly if needed

I don't feel strongly about the wording that's used at the end. I think I wrote "ignored" (without ellipsis) in the issue description because skipping tests is instantaneous, whereas running tests can take a while if the target needs to e.g. sample temperature once per seconds for a few seconds to check some requirement so one may see "running .." (long pause) and then new test.

[japaric]

(interesting that you also get an error from rustc about stability)

[japaric]

sorry, to clarify: I meant putting the allow in the expansion (proc-macro code) not in the input code. the semantics here should be following (this can be UI tested)

#[test]
#[ignore]
fn f() { // <- warning about `f` being `dead_code` MUST NOT be emitted
    let x = 42; // <- `dead_code` warning MUST be emitted here
}

I think it would be good to also test that compiler errors in ignored tests are emitted.
The expect semantic is that ignored tests are compiled but not executed.
A UI test like this can test that:

#[test]
#[ignore]
fn f() {
    let x: () = 42; //~ ERROR: type mismatch
}

[justahero]

The dead_code warning of an ignored function is handled by a recent change.

Unfortunately it's not easy to set up the suggested tests in the defmt-test crate using trybuild. The defmt-test crate is used as a library in a non-std environment, for example when set up from the app-template repo. I tried to add ui tests using trybuild but this works in std envs only.

[japaric]

spotted 2 issues

[japaric]

Thanks for working on this!

[japaric]

bors r+

[bors]

Build succeeded:

• ci

[jonas-schievink]

This will still call the test function if it has #[ignore] on it, leading to the issue reported in #731