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Modify cloneNode to handle shadow dom. #1

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Apr 25, 2022
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Modify cloneNode to handle shadow dom. #1

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88c5eaf
Modify cloneNode to handle shadow dom.
aschenoni Apr 18, 2022
7575b93
Clean up custom shadow serializing functions.
aschenoni Apr 20, 2022
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6 changes: 4 additions & 2 deletions packages/dom/src/serialize-dom.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,8 @@ import serializeCSSOM from './serialize-cssom';
import serializeCanvas from './serialize-canvas';
import serializeVideos from './serialize-video';

import { cloneNodeAndShadow, customOuterHTML } from './wc-clone';

// Returns a copy or new doctype for a document.
function doctype(dom) {
let { name = 'html', publicId = '', systemId = '' } = dom?.doctype ?? {};
Expand Down Expand Up @@ -32,7 +34,7 @@ export function serializeDOM(options) {

prepareDOM(dom);

let clone = dom.cloneNode(true);
let clone = cloneNodeAndShadow(dom);
serializeInputs(dom, clone);
serializeFrames(dom, clone, { enableJavaScript });
serializeVideos(dom, clone);
Expand All @@ -52,7 +54,7 @@ export function serializeDOM(options) {
}
}

return doctype(dom) + doc.outerHTML;
return doctype(dom) + customOuterHTML(doc);
}

export default serializeDOM;
64 changes: 64 additions & 0 deletions packages/dom/src/wc-clone.js
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@@ -0,0 +1,64 @@
/**
* Custom deep clone function that replaces Percy's current clone behavior.
* This enables us to capture shadow DOM in snapshots. It takes advantage of `attachShadow`'s mode option set to open
* https://developer.mozilla.org/en-US/docs/Web/API/Element/attachShadow#parameters
*/
const deepClone = host => {
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how do we know this (not-trivial) walker works ?
do we need any tests ? or is this code copy-pasted from somewhere ?

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@mmun mmun Apr 25, 2022 •
edited
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It's copied from https://stackoverflow.com/a/55540552 and modified a bit. I don't think this fork is really set up to run tests.

I'd like to see the code tidied up and tested but yeah...

let cloneNode = (node, parent) => {
let walkTree = (nextn, nextp) => {
while (nextn) {
cloneNode(nextn, nextp);
nextn = nextn.nextSibling;
}
};

let clone = node.cloneNode();
parent.appendChild(clone);

if (node.shadowRoot) {
if (clone.shadowRoot) {
// it may be set up in a custom element's constructor
clone.shadowRoot.innerHTML = '';
} else {
clone.attachShadow({
mode: 'open'
});
}

for (let sheet of node.shadowRoot.adoptedStyleSheets) {
let cssText = Array.from(sheet.rules).map(rule => rule.cssText).join('\n');
let style = document.createElement('style');
style.appendChild(document.createTextNode(cssText));
clone.shadowRoot.prepend(style);
}
}

if (node.shadowRoot) {
walkTree(node.shadowRoot.firstChild, clone.shadowRoot);
}

walkTree(node.firstChild, clone);
};

let fragment = document.createDocumentFragment();
cloneNode(host, fragment);
return fragment;
};

/**
* Sets up the document clone to mirror the result of Node.cloneNode()
* using the deep clone function able of cloning shadow dom
*/
const cloneNodeAndShadow = doc => {
let clonedDocumentElementFragment = deepClone(doc.documentElement);
clonedDocumentElementFragment.head = document.createDocumentFragment();
clonedDocumentElementFragment.documentElement = clonedDocumentElementFragment.firstChild;
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This code is pretty hacky. We should rewrite the logic here to avoid adding properties onto a fragment which don't exist.

return clonedDocumentElementFragment;
};

const customOuterHTML = docElement => {
return `<html class="hydrated">${docElement.getInnerHTML()}</html>`;
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@mmun mmun Apr 18, 2022 •
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The general approach would be to copy the attributes on the root element over instead of hard coding class="hydrated" (which a Stencil-specific thing)

};


export { cloneNodeAndShadow, customOuterHTML }