PopoverTarget: mergeRefs not memoized, causes infinite re-render loop

[kajtzu]

Bug description

In PopoverTarget (packages/core/src/components/popover-next/popoverTarget.tsx), mergeRefs is called unconditionally in the render body of a functional component:

const ref = mergeRefs(floatingData.refs.setReference, targetRef);

This produces a new ref callback on every render. When React sees a changed ref callback, it invokes the previous one with null and the new one with the DOM node. The setReference(null) triggers a floating-ui state update, which causes a re-render, which creates another new mergeRefs result — producing an infinite loop that crashes with:

Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate.

Notably, Blueprint's own JSDoc on mergeRefs already warns about this:

/**
 * Utility for merging refs into one singular callback ref.
 * If using in a functional component, would recomend using `useMemo` to preserve function identity.
 */
export function mergeRefs<T>(...refs: Array<React.Ref<T> | undefined>): React.RefCallback<T> {

PopoverTarget is a forwardRef functional component but does not follow this guidance.

Steps to reproduce

1. Render a PopoverNext whose parent re-renders frequently (e.g. connected to a Redux store or React Query cache that resolves synchronously on mount)
2. The page crashes immediately with a stack trace through floating-ui.react.mjs → floating-ui setReference → PopoverTarget

The crash is timing-dependent — it requires the parent to re-render fast enough that React's ref cleanup/re-assignment cycle doesn't settle. Synchronous cache hits (React Query, Redux selectors) reliably trigger it.

Suggested fix

Memoize the mergeRefs call in popoverTarget.tsx:

const ref = useMemo(() => mergeRefs(floatingData.refs.setReference, targetRef), [floatingData.refs.setReference, targetRef]);

Environment

• @blueprintjs/core 6.9.1 (also confirmed on develop branch HEAD)
• React 18.3.0
• @floating-ui/react (as bundled/re-exported by Blueprint)

[kajtzu]

Still present in latest, 6.15.0