Report 'prerender' navigation type accurately #75
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src/visuallyCompleteCalculator.ts
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| const navigationType = isBfCacheRestore | ||
| ? 'back_forward' | ||
| : // @ts-ignore activationStart is an experimental property | ||
| navigationEntry.activationStart > 0 |
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Can we check navigationEntry.type instead? If it's already prerender, then just pass it on. I guess I am wondering if there will be able mismatch between navigation type = prerender and activationStart > 0
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I did check this, but it turns out Chrome does not actually report 'prerender' correctly. This is in conflict with my reading of the spec.
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https://developer.chrome.com/blog/prerender-pages/#detecting-prerender-in-javascript
I guess checking activationStart it is then. Do we need to check document.prerendering for prerendering page (rather than prerendered page). I guess maybe we don't since we restart measurement on prerenderingchange anyways.
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👍 Oh, nice find.
Yes, that's right. The document.prerendering value will only be true during the prerender, and we never report TTVC before prerendering has finished.
ajhyndman
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In the case that a page was pre-rendered, we should report the 'prerender' navigation type, as defined in the W3 specification.
https://developer.mozilla.org/en-US/docs/Web/API/PerformanceNavigationTiming/type
https://w3c.github.io/navigation-timing/#sec-performance-navigation-types