fix(react-virtual): make directDomUpdates a no-op without containerRef

.changeset/direct-dom-no-container.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/react-virtual': patch
+---
+
+Make `directDomUpdates` a no-op for direct DOM writes when `containerRef` is omitted. Previously the virtualizer still wrote item positions while never sizing the container (a broken half-state). Now omitting `containerRef` skips all direct writes while still skipping re-renders, letting consumers own the DOM updates themselves (e.g. in `onChange`).

docs/framework/react/react-virtual.md

@@ -89,6 +89,8 @@ const virtualizer = useVirtualizer({
 
 > ⚠️ This flag is intended to be set once at mount. Toggling it (or `directDomUpdatesMode`) at runtime can leave stale inline styles on items and the container.
 
+> **Note:** If you omit `containerRef`, the virtualizer makes no direct DOM writes — it writes neither item positions nor the container size. You're then responsible for positioning items and sizing the container yourself (e.g. in `onChange`), while still benefiting from the skipped re-renders.
+
 #### Example
 
 ```tsx

packages/react-virtual/e2e/app/direct-dom-updates/main.tsx

@@ -10,6 +10,10 @@ const App = () => {
 
   const params = new URLSearchParams(window.location.search)
   const mode = (params.get('mode') ?? 'transform') as 'position' | 'transform'
+  // When set, the consumer omits `containerRef`. The virtualizer must then make
+  // no direct DOM writes at all (neither item positions nor container size),
+  // leaving the consumer to own them — while still skipping re-renders.
+  const noContainer = params.get('noContainer') === '1'
 
   const renderCount = React.useRef(0)
   renderCount.current += 1
@@ -40,7 +44,7 @@ const App = () => {
         style={{ height: 400, overflow: 'auto' }}
       >
         <div
-          ref={rowVirtualizer.containerRef}
+          ref={noContainer ? undefined : rowVirtualizer.containerRef}
           id="inner"
           style={{ position: 'relative', width: '100%' }}
         >

packages/react-virtual/e2e/app/test/direct-dom-updates.spec.ts

@@ -89,5 +89,41 @@ for (const mode of ['position', 'transform'] as const) {
         expect(style).toMatch(/translate3d\(0px,\s*20000px,\s*0px\)/)
       }
     })
+
+    test('without containerRef the virtualizer makes no direct DOM writes but still skips re-renders', async ({
+      page,
+    }) => {
+      await page.goto(`/direct-dom-updates/?mode=${mode}&noContainer=1`)
+
+      // Container size is NOT written by the virtualizer when containerRef is omitted.
+      const inner = page.locator('#inner')
+      const innerStyle = (await inner.getAttribute('style')) ?? ''
+      expect(innerStyle).not.toMatch(/height:\s*\d/)
+
+      // Item positions are NOT written by the virtualizer either.
+      const first = page.locator('[data-testid="item-0"]')
+      await expect(first).toBeVisible()
+      const firstStyle = (await first.getAttribute('style')) ?? ''
+      if (mode === 'position') {
+        expect(firstStyle).not.toMatch(/top:\s*\d/)
+      } else {
+        expect(firstStyle).not.toMatch(/transform:/)
+      }
+
+      // Re-render skipping still applies: scrolling by one item (absorbed by
+      // overscan) must not trigger React re-renders.
+      const initialRenders = Number(
+        await page.locator('[data-testid="render-count"]').textContent(),
+      )
+      await page.locator('#scroll-container').evaluate((el, by) => {
+        el.scrollTop = by
+      }, ITEM_SIZE)
+      // Give onChange a chance to fire.
+      await page.waitForTimeout(50)
+      const afterRenders = Number(
+        await page.locator('[data-testid="render-count"]').textContent(),
+      )
+      expect(afterRenders - initialRenders).toBeLessThanOrEqual(2)
+    })
   })
 }

packages/react-virtual/src/index.tsx

@@ -111,10 +111,10 @@ function useVirtualizerBase<
     instance: Virtualizer<TScrollElement, TItemElement>,
   ) => {
     const state = directRef.current
-    if (!state.enabled) return
+    if (!state.enabled || !state.container) return
 
     const totalSize = instance.getTotalSize()
-    if (state.container && totalSize !== state.lastSize) {
+    if (totalSize !== state.lastSize) {
       state.lastSize = totalSize
       const sizeAxis = instance.options.horizontal ? 'width' : 'height'
       state.container.style[sizeAxis] = `${totalSize}px`