ResizeObserver loop completed with undelivered notifications - flushSync called synchronously inside ResizeObserver callback (regression from 6.1.18 to 7.0.0)

Reduced Test Case

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• I understand

Which connector are you using (React/Angular/etc)?

Angular

Bug Description

We upgraded from 6.1.18 to 7.0.0 and immediately get "ResizeObserver loop completed with undelivered notifications" on every calendar render.

Root cause found in packages/core/src/component-util/resize-observer.ts:

const globalResizeObserver = new ResizeObserver((entries) => {
    isHandling = true;
    // ... process entries ...
    flushSync(() => {   // <-- synchronous DOM mutations inside ResizeObserver
        flushAfterSize();
        isHandling = false;
    });
});

Calling flushSync synchronously inside the ResizeObserver callback causes the browser to flag it as a loop on every render. Fix that works — use requestAnimationFrame instead, consistent with how afterSize() already handles the non-ResizeObserver path in the same file:

requestAnimationFrame(() => {
    flushSync(() => {
        flushAfterSize();
        isHandling = false;
    });
});

Tested locally — completely eliminates the error while calendar works correctly.