Weak type checking in parser following JSON $refs update

[Sidnioulz]

Versions

main as of 2025-10-05

Node.js version

24.4.1

OS + version

Linux 6.16.8-arch3-1

Description

In packages/parser/src/parse/token.ts:

  const $extensions = getObjMember(node, '$extensions');
  if ($extensions) {
    const modeNode = getObjMember($extensions as momoa.ObjectNode, 'mode') as momoa.ObjectNode;
    for (const mode of Object.keys((token.$extensions as any).mode)) {
      const modeValue = (token.$extensions as any).mode[mode];
      token.mode[mode] = {
        // ...
      };
    }
  }

(token.$extensions as any).mode can be undefined and is not guarded, causing an error when running TZ with an outdated tokens.json. The error is cryptic as it says "Cannot convert undefined or null to object".

Reproduction

Do a quick merge/rebase of the tokens listing branch, and without editing fixtures, run tests.

Expected result

I'd expect the parser to detect what exactly is missing and to provide a good error message.

Considering that $extensions.mode was previously assumed to exist when $extensions did, a message tailored at existing TZ users, telling them to update JSON files, could be relevant.

Extra

• I’m willing to open a PR (see CONTRIBUTING.md)