This is a follow-up issue started at #186 (comment).

It is unclear from the recently added Annotation docs if ::debug/::warning/::error messages support multiline text in the {message} placeholder.

Why it is important? These Annotations can be used by various code linters and other similar tools, but their output easily could be spanned to multiple lines, for example:

pylint output:

W:108: Operator not followed by a space
     print >>sys.stderr, 'Unable to match %r', line
            ^

Rust compiler output:

warning: comparison is useless due to type limits
  --> example/src/lib.rs:20:8
   |
20 |     if pid < 0 {
   |        ^^^^^^^
   |
   = note: `#[warn(unused_comparisons)]` on by default

It would be nice to clarify if it is possible to use multiline strings over there and it is expected to be working correctly in the future.