Is there a way to create warnings?

[matthew-dean]

This morning, I was exploring the Chevrotain code to see if there was any way I could create warnings instead of errors.

In other words, having code like:

$.RULE('valueSequence', () => {
      $.OR([
        {
          GATE: createWarning(),
          ALT: EMPTY_ALT()
        }
      ])
      $.AT_LEAST_ONE(() => $.SUBRULE($.value))
    })

There are cases where the non-existence of a rule or value is problematic, but it's not necessarily a parsing problem. I'd love to be able to use all the plumbing of creating error messages, but without a thrown error.

OR would the advice be that this shouldn't be part of the parser, and is something more valid for a CSTVisitor?

[bd82]

I would personally try to keep the parser for pure grammar concerns.
Although you could consider these warnings to be either as part of the grammar or part of the linter, perhaps you could even have different types of warnings handled in different places. (grammar deprecation warning vs style recommendation).

Anyhow, there does not seem to be much plumbing in the error messages creation, so I am not sure code re-use is a major concern here.

If you think it will be convenient / easier to collect the warnings during the parsing, that is fine.
Simply collect them in a new array instance member on your parser (separate from the errors).