Description

This PR modernizes the composeSignals helper by leveraging the native AbortSignal.any() API when it is available in the environment (Node.js 20+, modern browsers).

Key Changes

• Performance & Simplicity: Uses AbortSignal.any() to create a composite signal from multiple input signals and/or a timeout. This is more efficient and cleaner than the manual event listener attachment approach used previously.
• Backward Compatibility: Fully retains the existing robust implementation as a fallback for older environments that do not support AbortSignal.any.
• Resource Management: Implements proper cleanup logic (unsubscribe) for timeout signals to ensuring timers are cleared correctly when requests complete, matching the behavior expected by the fetch adapter.

Testing

I have verified these changes locally to ensure no regressions:

• Unit Tests: Passed test/unit/helpers/composeSignals.js, confirming that signal composition and timeouts work as expected.
• Integration Tests: Passed test/unit/adapters/fetch.js, confirming that real-world requests, timeouts, and cancellations continue to function correctly.

Checklist

• Code follows the project's coding standards.
• Tests have been run and pass locally.
• Changes are backward compatible.

Summary by cubic

Modernizes composeSignals to use AbortSignal.any when available, simplifying signal composition and ensuring proper timeout cleanup. Keeps a safe fallback for older runtimes and matches fetch adapter expectations.

• New Features

  • Uses AbortSignal.any to combine input signals and an optional timeout in supported environments.
  • Retains listener-based fallback for older environments.
  • Adds compositeSignal.unsubscribe to clear timeout timers.

• Testing

  • No new tests; existing composeSignals and fetch adapter tests pass, including after the latest v1.x merge.
  • Optional: add a feature-detection test to cover the AbortSignal.any path.

^{Written for commit 64f76e0. Summary will update on new commits.}