Banish the ? Operator in Backend JS
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	cmassaro
	Oct 20 2025, 7:38 PM

Description

This operator is useful in TypeScript, where one can reason about objects. It is horribly dangerous in the Wikifunctions backend, because it transparently ignores some REALLY BAD errors.

Desired behavior/Acceptance criteria (returned value, expected error, performance expectations, etc.)

eliminate all current uses of the ? operator
DO NOT USE THIS OPERATOR IN FUTURE

Remove all the non-applicable tags from the "Tags" field, leave only the tags of the projects/repositories related to this task

Completion checklist

Before closing this task, review one by one the checklist available here: https://www.mediawiki.org/wiki/Abstract_Wikipedia_team/Definition_of_Done#Back-end_Task/Bug_completion_checklist

Details

Related Changes in Gerrit:

	Subject	Repo	Branch	Lines +/-
	wikifunctions: Upgrade orchestrator from 2025-11-04-215809 to 2025-11-08-223341	operations/deployment-charts	master	+1 -1

Customize query in gerrit

Related Changes in GitLab:

	Title	Reference	Author	Source Branch	Dest Branch
	execute: Avoid optional chaining to make our code more explicit	repos/abstract-wiki/wikifunctions/function-orchestrator!482	jforrester	T407791	main

Customize query in GitLab

Event Timeline

cmassaro created this task.Oct 20 2025, 7:38 PM

cmassaro triaged this task as High priority.

cmassaro edited projects, added Abstract Wikipedia team (26Q2 (Oct–Dec)); removed Abstract Wikipedia team.Oct 22 2025, 5:39 PM

cmassaro moved this task from Incoming to Ready on the Abstract Wikipedia team (26Q2 (Oct–Dec)) board.Oct 22 2025, 5:57 PM

I think we can simply enforce this via "no-unsafe-optional-chaining": "error" in .eslintrc.json.

In T407791#11350677, @Jdforrester-WMF wrote:

I think we can simply enforce this via "no-unsafe-optional-chaining": "error" in .eslintrc.json.

Alas, no, that only finds "unsafe" where eslint knows that providing null will explode — which isn't the concern here.

jforrester opened https://gitlab.wikimedia.org/repos/abstract-wiki/wikifunctions/function-orchestrator/-/merge_requests/482

execute: Avoid optional chaining to make our code more explicit

Beyond the code above, we have two other uses of optional chaining:

In fetchObject.ReferenceResolver:

		Object.defineProperty( this, 'createCustomSpans', {
			get: function () {
				return this.invariants_?.orchestratorConfig?.createCustomSpans ?? null;
			}
		} );

In the boiler-plate in app.js (also in function-evaluator):

	// Default to old service-runner config shape or override with top level
	// TODO: Make config top level in helmchart
	app.conf = {
		// eslint-disable-next-line unicorn/no-useless-fallback-in-spread
		...( conf.services?.[ 0 ]?.conf ?? {} ),
		...conf
	}; // this app's config options