Fix access to undefined exception #4219
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I should note, I hit this on 10.18.1. I tried updating to 10.19.2 and the issue persisted. I identified the issue and verified the fix by adding the I opened on 'main' as I see the same code exists there, but I can backport if desired. |
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Mind giving some way to reproduce this issue as props are defaulted to an object https://github.com/preactjs/preact/blob/main/src/create-element.js |
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It was in the middle of a larger codebase and only happened sporadically, but I'll try and conjure up a minimal repo. I assumed it could be null as a few lines later (427) it seems to check if it could have been null on the old node (via |
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A repro or test case would be needed either way so we can prevent regressions. The old node is indeed nullable, this is during the creation scenario but then the new one is still defined |
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OK. Just narrowed it down and got a minimal repro. It's a bug in my app's code, but I believe it still shouldn't be throwing an unhandled exception here. Basically, in one scenario it was passing an object for what should have been a string which is rendered in a text node location. This renders without error first time through, but on the re-render on changing some state unrelated to the problematic node, it throws the error. Load the below on an empty document, and when you click the checkbox to cause the re-render you'll see the issue. As the commented line states, if data is a string instead of an object (as it was supposed to be), then it re-renders fine. import { render } from "preact";
import { useState } from "preact/hooks";
window.onload = () => {
// *** If data is a string, it works fine ***
const data = { a: 10, b: "hello" };
render(<ReproApp data={data} />, document.body);
};
function ReproApp({ data }: any) {
const [showDetail, setShowDetail] = useState(false);
const toggleDetail = () => {
setShowDetail(!showDetail);
};
return (
<>
<p>Check the box to cause the error</p>
<input type="checkbox" checked={showDetail} onClick={toggleDetail} />
<div>{data}</div>
</>
);
} |
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Thanks for providing a minimal test reproduction! Took the liberty of updating the PR. The observed issue is a symptom of another cause in that recent refactors lead to invalid vnodes being passed to |
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Great! Thanks for the 'correct' fix, and super-fast turnaround. I love the project and use it whenever I can, so thanks for your work on it. |
andrewiggins
approved these changes
Nov 27, 2023
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Dec 13, 2023
Moving to 10.19.3 as it has my picture on it. (For a reason - it fixes the issue I hit when developing the widgets, preactjs/preact#4219).
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Running some code locally and I was regularly hitting an error
Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'is'). I tracked it down to the line fixed in this PR.It would appear that sometimes
newVNode.propsmay be undefined, so guarding against that.