Adopt+upgrade template fragments after processing for parts #831
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Importing the node can cause any custom elements to upgrade, and non-compliant custom elements can cause DOM mutations. If this happens before we process the template parts, our `part.index`s walking will be broken. So, it has to wait till afterwards. But we still have to return upgraded elements before the template part's interact with the DOM. Luckily, we just adopt and upgrade them after the processing. Fixes lit#561.
jridgewell
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The original issue outlined in #561 is that we don't know if the clone-then-adopt approach has a significant performance impact compared to the direct import we have now. This change does simplify Custom Element handling and fixes several edge cases, but we should get some benchmarks and measure the performance impact before making this change. |
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https://jsbench.github.io/#7949baf66c5f9a0a49f478c2a3ee927e I can't really determine if it's faster or slower, the stddev is really high. Might be due to GC? |
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This is the more correct ordering, so ultimately I'd like to take this change. On the micro benchmark, it seems clear that in the presence of custom elements, the difference is negligible, and neither benchmark have real script work in between steps, which might reduce the difference even further into noise. |
Importing the node can cause any custom elements to upgrade, and non-compliant custom elements can cause DOM mutations. If this happens before we process the template parts, our `part.index`s walking will be broken. So, it has to wait till afterwards. But we still have to return upgraded elements before the template part's interact with the DOM. Luckily, we just adopt and upgrade them after the processing. Fixes lit#561.
Importing the node can cause any custom elements to upgrade, and non-compliant custom elements can cause DOM mutations.
If this happens before we process the template parts, our
part.indexs walking will be broken. So, it has to wait till afterwards.But we still have to return upgraded elements before the template part's interact with the DOM. Luckily, we just adopt and upgrade them after the processing.
Fixes #561.