Issue Review: cloudflare/workers-sdk#8792

Summary

fetchMock from cloudflare:test doesn't intercept requests with square brackets in query parameters (e.g., arraykey[]=a&arraykey[]=b).

Findings

• Created: 2025-04-04
• Updated: 2025-10-30
• Version: vitest-pool-workers@0.8.10 → 0.12.6
• Component: vitest-pool-workers
• Labels: bug
• Comments: 1

Key Evidence

• Upstream fix exists but not applied: The root cause was in undici's MockAgent. Fixed via nodejs/undici#4148 (merged April 21, 2025) which added acceptNonStandardSearchParameters option.

• Workers-sdk has updated undici: PR #11967 (merged Jan 19, 2026) updated undici from 7.14.0 to 7.18.2, which includes the fix.

• Fix not utilized: The current fetch-mock.ts creates MockAgent as:

  export const fetchMock = new MockAgent({ connections: 1 });
  

  It does NOT pass acceptNonStandardSearchParameters: true, so the fix is not active.

• Maintainer confirmed upstream: @dario-piotrowicz identified this as an undici issue and created the upstream issue which has now been fixed.

Recommendation

Status: KEEP OPEN

Reasoning: The upstream fix in undici is available and workers-sdk has updated to a version that includes it. However, vitest-pool-workers needs to be modified to pass acceptNonStandardSearchParameters: true when creating the MockAgent instance. This is a straightforward fix.

Action: Implement the fix by updating fetch-mock.ts to use the new undici option:

export const fetchMock = new MockAgent({ 
  connections: 1,
  acceptNonStandardSearchParameters: true 
});

Suggested Comment

The upstream fix is now available. Undici added the acceptNonStandardSearchParameters option in nodejs/undici#4148, and workers-sdk has updated to undici 7.18.2 which includes this fix.

To resolve this issue, vitest-pool-workers needs to be updated to pass this option when creating the MockAgent:

export const fetchMock = new MockAgent({ 
  connections: 1,
  acceptNonStandardSearchParameters: true 
});

This would be a simple one-line change in packages/vitest-pool-workers/src/worker/fetch-mock.ts.