Contribution; error handling

Strudel
1

A class I am in for university uses strudel a lot and we noticed that some of the error messaging was tough to read for beginner users. For my final project for the class I hope to fix this issue and contribute to the software. I was thinking of adding some more clearly defined error messages. For example, a missing paratheses currently reads in the error bar as "unexpected token at x:y". Changing it indiciate what character is missing for some syntax issue or possibly highlighting the location of the error for easier debugging for novice users. Would love and appreciate any feedback regarding on the feasibility of this as well as how best to go about this?? I have already taken a look around the repo and think I know where it would be best to work (Krill and/or code mirror packages).

1 Like
2

I think highlighting of the location would be huge. I expect you’ll mostly be working in the krill file, as you say. I wish you luck, I recently did some diving into there and it was not trivial! Happy to give help where I can

3

Would love some help! I am planning on starting to dive deeper into this in about a week. I would really appreciate some guidance!

4

So here is my plan so far

Background/overview:

  • the mini notation for the parser in is “krill-parser.js”
    • this produced an error object called peg$SyntaxError with the fields, expected, found, and location
    • this is then sent to the mini.mjs and reformatted
  • in the JS transpilation
    • uses a Acorn parser
    • produces your basic stantard javascript SyntaxError
  • in runtime eval
    • errors is going thru repl.mjs via the evalError
  • UI
    • stored in UserFacingMessage.jsx
    • just renders error.message

What is needed to be done

  • modify mini.mjs to improve the mini notation error messages

  • add some visual element to indicate where error is

  • change the error display component (maybe too much)

  • select the rule set

    • notation (maybe best to just start here)
      • missing brackets “bd [sd”
      • missing paren “bd(3,8”
      • invalid char “bd $ sd”
      • unclosed angle bracket “<bd sd”

  • build out the tests

    Screenshot 2026-04-09 at 12.40.33 PM
    Screenshot 2026-04-09 at 12.40.33 PM1032Ă—456 11 KB

First run thru

  • errorHighlight.mjs
    • codemirror extension adds the red highlight
    • exports to the highlight error
  • catches and just adds the region [from,to]
  • bubbles up to strudlelmirror

restrictions, only shows first error.

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Nice work so far!