Changing RUSTFLAGS to use JSON errors causes whole rebuild of a project

[White-Oak]

I beleive it's intended, but we use RUSTFLAGS to provide --error-format=json to rustc to use JSON errors in a linter (issue AtomLinter/linter-rust#77), so whenever I switch between terminal and editor, cargo rebuilds the whole project, which can take a long time.

I've heard that JSON errors are to be in stable soon -- will there be some kind of cargo switch to avoid changing RUSTFLAGS to avoid the rebuilding of a project?

[matklad]

• will there be some kind of cargo switch to avoid changing RUSTFLAGS to avoid the rebuilding of a project?

Yes it will: #3000!

[alexcrichton]

This is indeed a problem! And intended to be solved with #3000, so closing in favor of that.

(in the sense that this is intended behavior today but the intended implementation strategy is #3000)