Allow line numbers in addition to test name for focusing tests

[thegranddesign]

When working in an editor and scripting test runs in an automated fashion, it's much more practical to be able to specify the line number rather than trying to parse the file to determine the test name.

For example:

#[cfg(test)]
mod tests {
    #[test]
    fn it_can_add_things() {
        assert!(2 + 2, 4)
    }
}

It's quite difficult to parse backwards line by line to find the previous fn statement (which is problematic in itself) and then pull out the it_can_add_things section of the line before finally constructing the full command.

All editors have a capability to determine the current line and thus, assuming I'm on line 5 (the assert line), running something like cargo test 5 or cargo test --lines=5 is very straightforward.

Bonus points would include ranges and comma separated lists: cargo test --lines=1-10,21

This feature would effectively allow "run the test under the cursor" which is something that I do constantly during the day in other languages.

[Ixrec]

Maybe I'm missing something, but "run the test under the cursor" seems like a feature that should be implemented as a macro/plugin for the editor, while rust/cargo should just take a test name. Especially since your editor might be auto-editing the file for various reasons, including auto-formatting that might change line numbers around at (from rust/cargo's point of view) random times.

But I totally agree that "run the test under the cursor" should get implemented.

[thegranddesign]

I absolutely get what you’re saying. I think the point I’m trying to make is that this is a general requirement for editors and making each editor have its own logic for doing something like this (each of which can have its own set of bugs) in each of their own plugins seems like an inelegant solution.

I agree that this would have to be determined prior to any code transforms (eg macros) happening.

[thegranddesign]

As far as auto formatting in the editor, that is absolutely the user’s/editor’s job to deal with. That’s not rust’s responsibility. As long as there’s a way to run the tests on a given line, that should be all rust has to care about.

[matklad]

It is certainly possible to do this on the IDE level, IntelliJ does this, and RLS should be able to too.