The xhr adapter's onabort, onerror, ontimeout, and onCanceled handlers reject the promise but never run done(), so the listener they added to cancelToken or AbortSignal stays attached. If you reuse one token or controller for many requests, this turns into a memory leak: every failed request retains a listener holding the full config.

Quick repro:

const { XMLHttpRequest } = require('xmlhttprequest');
globalThis.XMLHttpRequest = XMLHttpRequest;
const axios = require('axios');

(async () => {
  const source = axios.CancelToken.source();
  for (let i = 0; i < 500; i++) {
    await axios.get('http://127.0.0.1:1/', {
      cancelToken: source.token,
      adapter: 'xhr',
      timeout: 500,
      data: { blob: new Uint8Array(100_000).fill(i & 0xff) },
    }).catch(() => {});
  }

  console.log('leaked listeners:', source.token._listeners.length);
  // v1.15.1: 500 (about 550 MB retained after GC)
  // with this fix: 0
})();

The fix just adds a done() call to each of the four error handlers. The success path and the http/fetch adapters already do this.

Summary by cubic

Fixes a memory leak in the axios XHR adapter by calling done() on error, timeout, abort, and cancel paths to unsubscribe cancelToken/AbortSignal listeners. Prevents listener buildup when reusing tokens or controllers.

Description

• Summary of changes: Call done() in onabort, onerror, ontimeout, and onCanceled to remove listeners; aligns with success path and http/fetch adapters.
• Reasoning: Failed requests previously rejected without detaching listeners, retaining config/request references and growing memory.
• Additional context: No behavior change to cancellation; this is cleanup on failure paths only.

Docs

• Update /docs/ cancellation guide to note XHR now auto-cleans listeners on error/abort/timeout and that reusing tokens/controllers no longer leaks listeners.

Testing

• Added browser tests verifying:
  • cancelToken listener is removed after network error, timeout, and browser abort.
  • AbortSignal listener count returns to zero after a network error.
• No additional tests needed.

Semantic version impact

• Patch.

^{Written for commit 8653298. Summary will update on new commits.}