Description
Describe the bug
Memory is leaked when a component is updated.
My Electron (happens in Chrome also, see below!) application has a progress display (status text showing transferred bytes, progress bar) which updates very often. As Electron has the V8 Memory Cage enabled since version 21, limiting the memory to a few gigabytes (they say 4 GB, but it is 3 GB in my tests), the application frontend goes away after a while (leaving an empty BrowserWindow).
After spending a lot of time tracking down this issue, I was able write a simple reproduction - see below - which fills up the memory very fast in Chrome (see Chrome DevTools -> Memory).
To Reproduce
Use a current version of Chrome.
import { render, useState } from 'preact/compat';
// The only purpose of ChildComponent is to create a complex tree, eating up memory fast.
interface ChildComponentProps {
readonly level: number;
}
function ChildComponent({ level }: ChildComponentProps) {
return (
<div>
<div>{new Date().valueOf().toString()}</div>
{level < 4 && Array(3).fill(0).map((_, index) => (
<ChildComponent key={index} level={level + 1} />
))}
</div>
);
}
function RootComponent() {
const [counter, setCounter] = useState(0);
setTimeout(() => setCounter(counter + 1), 0); // simply force updating all the time
return (
<div>
<span>{counter.toString()}</span>
<div style={{ display: 'none' }}>
<ChildComponent level={0} />
</div>
</div>
);
}
const rootElement = document.getElementById('root');
render(<RootComponent />, rootElement!);Expected behavior
Memory usage should remain quite constant. It should definitely not lead to an out-of-memory error.