Issue

In experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts at line 423,
the current logic discards RequestInit options when a Request object is passed as the
first argument to fetch().

Current Code

const options = args[0] instanceof Request ? args[0] : args[1] || {};

When fetch is called as fetch(request, requestInit), the requestInit (args[1]) is completely ignored, which violates the Fetch API specification.

Expected Behavior

According to the Fetch API spec, when a Request object is passed along with a RequestInit, the init options should override or extend the request's properties.

Proposed Fix

const options = args[0] instanceof Request 
  ? new Request(args[0], args[1]) 
  : { url: args[0], ...args[1] };

This ensures proper merging of request initialization options.

Affected Code