Reduce unnecessary DOM attribute reads#2486
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marvinhagemeister merged 5 commits intomasterfrom Apr 21, 2020
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JoviDeCroock
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Apr 20, 2020
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That's a really good find! We could make it shorter by just doing if (excessDomChildren) but yes nothing major, awesome work!
andrewiggins
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Apr 20, 2020
| expect(style.zIndex.toString()).to.equal(''); | ||
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| it('should remove existing attributes', () => { |
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These tests were under the "style attribute" describe block. I just moved them to the bottom of this file out of the "style" describe block since they don't have anything to do with the style attribute.
| expect(serializeHtml(scratch)).to.equal('<div><span>Bye</span></div>'); | ||
| }); | ||
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| it('should not read DOM attributes on render without existing DOM', () => { |
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This is the new test for this PR
developit
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Apr 21, 2020
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Oh wow, this is a great find. Likely a nontrivial performance win for client side routing and also for our suspense resumption
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I think there are 4 different "modes" of diffing that Preact can be in (ignoring things like suspense for now).
!isHydratingcheckrenderwhen the container contains existing DOM. This behavior compares the existing DOM with the specified VNodes including attributes.preact-routerand rendering an entirely new route client side. Preact creates the DOM from scratch. Because the DOM is created entirely from scratch, there are no attributes to be read.This PR fixes a bug where the
attributesproperty was being read in case 4. Since this is a fairly common situation, I figured skipping theattributesread would be beneficial.