Priority Queue: Fix for environments that don't have window defined

[p-jackson]

Description

Importing @wordpress/priority-queue, directly or indirectly, into an environment without window causes an error.

For example including the following in a test file so you can test a reducer:

const { combineReducers } = require( '@wordpress/data' );

and then running jest --env=node will fail with a "window is not defined" error.

The erroring code was added in #19282, and it looks like it was supposed to guard against this but there was just a typo.

How has this been tested?

I've tested this change against the test suite where I'm getting the errors and it resolves the issue.

Types of changes

Bug fix. I can't think of any situations where this would break existing code. The branch that includes the mock requestIdleCallback implementation is basically in a if ( false ) { ... } block at the moment, so I can't think of a way that any code would start using the wrong implementation.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[ramonjd]

Nice spotting. Would there by any chance of getting this in for 7.6.0 @aduth ?

[gziolo]

I can publish this fix to npm once merged.

[sirreal]

Interesting that no-constant-condition lint rule didn't catch this, I suppose that's because undefined can be a bound name?

[sirreal]

Thanks! This looks like a straightforward bug fix.

It looks like this bug would prevent the fallback function from ever being used, so I wanted to verify this works as expected. I changed a few things to rely on the typechecker:

/**
 * @return {Window['requestIdleCallback'|'requestAnimationFrame']}
 */
export function createRequestIdleCallback() {
	if ( typeof window === 'undefined' ) {
		/**
		 * @param {Parameters<Window['requestAnimationFrame']>[0]} callback
		 */
		const requestIdleCallback = ( callback ) => {
			setTimeout( () => callback( Date.now() ), 0 );
			return -1;
		};
		return requestIdleCallback;
	}

	return window.requestIdleCallback || window.requestAnimationFrame;
}

export default createRequestIdleCallback();

Notes:

• Narrow the type to satisfy Window['requestIdleCallback'|'requestAnimationFrame']
• Type the returned function parameter
• Date.now() is a number, but the requestIdleCallback callback parameter expects an IdleDeadline, which is more complex. number does satisfy the callback of requestAnimationFrame.
• Returns a number handle. -1 seems safe as it shouldn't collide, however if window is undefined, and cancelIdleCallback doesn't exist, they're unlikely to ever be cancelled 🙂

[gziolo]

I cherry-picked this commit to wp/trunk to ensure it’s included in the next npm release. I believe @jorgefilipecosta will do the npm publish on Monday as part of the WordPress release cycle.

[aduth]

Thanks all for managing this, and sorry for having introduced this careless error 😬