[material-ui][ButtonBase] Every interaction on a `disableRipple` button permanently leaks its event object (LazyRipple `mounted` promise never settles)

[dizhurnikita]

Steps to reproduce

Live example: https://codesandbox.io/s/s44gdq
(the same app standalone, best for taking heap snapshots: https://s44gdq.csb.app)

The app is one Button and one Dialog under a theme with:

createTheme({
  components: {
    MuiButtonBase: { defaultProps: { disableRipple: true } },
  },
});

1. Open https://s44gdq.csb.app and DevTools → Memory.
2. Take a heap snapshot; in the Summary view search MouseEvent and note
   the count (~0).
3. Click Simulate 100 clicks (it dispatches 100 real
   mousedown/mouseup pairs at the plain Button).
4. Take a second snapshot and search MouseEvent again: ~200 new objects
   (one per mousedown/mouseup), and they are never collected. Each one's
   retainer path is:
   nativeEvent of SyntheticBaseEvent ← args of the queued closure ←
   PromiseReaction ← reactions_or_result of Promise
   (= LazyRipple.mounted) ← mounted of LazyRipple ← the live
   button's fiber.
5. To see the detached-DOM impact: open and close the dialog 3 times,
   snapshot again, search Detached — 3 detached MuiDialog-container
   trees are retained, one per open/close cycle, held by the same chain
   (the opener button's focus/blur event references dialog content via
   relatedTarget).

Current behavior

When ripples are disabled (e.g. theme-wide MuiButtonBase: { defaultProps: { disableRipple: true } }), every mousedown/mouseup/blur/touch on every ButtonBase queues a promise reaction that is never released, capturing the event object. Events whose target/relatedTarget sit in later-removed DOM (a closed Dialog, an unmounted view) pin those entire detached trees for the page lifetime. Long-lived SPAs accumulate this on every click, forever.

Closing a MUI Dialog focuses the opener button; the blur/focus event's relatedTarget is an element inside the dialog. Heap snapshots show one retained detached dialog tree per open/close cycle, each held by a chain similar to this one:

detached MuiDialog-container
  <- relatedTarget of (FocusEvent)
  <- (bound arguments) [event] of the queued reaction closure
  <- PromiseReaction chain
  <- reactions_or_result of Promise            // LazyRipple.mounted
  <- "mounted" of LazyRipple
  <- __reactProps$…​.onFocus of the live opener <button>

4 opens → 4 retained dialog copies (~130 nodes each). Reproduced independently of the dialog: every ButtonBase interaction adds one pending reaction + event.

Expected behavior

Ripple actions should not retain event objects indefinitely when disableRipple is set; mounted should settle regardless of whether a TouchRipple mounts.

Context

Found while investigating a memory-growth issue in a long-lived SPA using a theme-wide disableRipple.

Suggested fix

In LazyRipple.mountEffect, settle the promise even when no ripple rendered — queued actions already no-op through ref.current?.:

   mountEffect = () => {
     if (this.shouldMount && !this.didMount) {
       if (this.ref.current !== null) {
         this.didMount = true;
-        this.mounted.resolve();
       }
+      this.mounted.resolve();
     }
   };

Would be happy to open a PR for this.

Your environment

npx @mui/envinfo from the reproduction project:

  System:
    OS: Linux 6.6 Ubuntu 24.04.1 LTS 24.04.1 LTS (Noble Numbat) (WSL2)
  Binaries:
    Node: 22.18.0 - /usr/bin/node
    npm: 12.0.1 - /usr/bin/npm
    pnpm: Not Found
  npmPackages:
    @emotion/react: latest => 11.14.0
    @emotion/styled: latest => 11.14.1
    @mui/core-downloads-tracker:  9.3.1
    @mui/material: latest => 9.3.1
    @mui/private-theming:  9.3.0
    @mui/styled-engine:  9.3.0
    @mui/system:  9.3.0
    @mui/types:  9.3.0
    @mui/utils:  9.3.0
    @types/react: ^18.3.3 => 18.3.31
    react: ^18.3.1 => 18.3.1
    react-dom: ^18.3.1 => 18.3.1
    typescript: ^5.5.3 => 5.9.3

Browser: Chrome 151.0.7922.76 (Windows), also reproduced in headless
Chromium. Originally found on @mui/material 6.1.1 + React 18 in a
production app; the useLazyRipple code is unchanged on current master
(checked 2026-08-19).

Search keywords: LazyRipple, disableRipple, mounted, ripple leak

[github-actions]

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