refactor(core): prefetch/preload refactor #7282
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⚡️ Lighthouse report for the changes in this PR:
Lighthouse ran on https://deploy-preview-7282--docusaurus-2.netlify.app/ |
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Size Change: -1 B (0%) Total Size: 805 kB ℹ️ View Unchanged
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Hmmm, zero size reduction. Slightly disappointed. The pnpm failure is unrelated. It's because pnpm 7.0 was released yesterday with pnpm/pnpm#4427. I will follow-up to fix it. |
| prefetch: (url: string) => false | Promise<void[]>; | ||
| preload: (url: string) => false | Promise<void[]>; |
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Nit but what's the advantage of having void[] here?
Maybe it would be better to use await Promise.all([]) and just have Promise<void>?
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Ahhh... you are right. Not a huge problem though.
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Ah, wait, we can't use await. We never use async-await in client code because that bloats the bundle (in fact I also want to reduce ?? and ?. usages). So in order to make it return void, we have to chain another .then(() => {}) which is not really ideal.
In addition, when it can't prefetch, false is returned synchronously, instead of being wrapped in a promise.
Pre-flight checklist
Motivation
With this change:
Setinstead of an object as the memoization layer, which should be more performant & has better semantics.prefetchmemoization has been deduplicated.prefetchHelpernow does not memoize on itself; onlywindow.docusaurus.prefetchdoes. This is fine, because we don't callprefetchHelperdirectly anywhere else.window.docusaurus.preloadandwindow.docusaurus.prefetchnow returnPromise<void[]>instead oftrue, which can allow external callers to wait for them instead of having floating promises.Test Plan
Prefetching work the same. You can confirm by scrolling down a page and see the network cascade expanding whenever a new link is in viewport.