fix: dispatch error instead of load when XMLHttpRequest completes without a response

[LoraBaek]

Summary:

When the native networking layer emits didCompleteNetworkResponse with a falsy error but no didReceiveNetworkResponse was ever delivered for that request, XMLHttpRequest.__didCompleteResponse treats the request as successful and dispatches load while status is still 0.

whatwg-fetch (which backs the global fetch in React Native) then runs new Response(body, {status: 0}) inside a setTimeout in xhr.onload. The Response constructor throws RangeError: Failed to construct 'Response': The status provided (0) is outside the range [200, 599]. Because the throw happens outside the promise chain, the fetch() promise never settles, no catch can observe it, and in a release build the uncaught error terminates the app.

We hit this in production (Android 16, Hermes, RN 0.83.10) on a plain HTTPS GET. Sentry breadcrumbs show the XHR finishing with status_code: 0, immediately followed by the fatal RangeError (mechanism onerror, handled: no). The device reported itself online over Wi-Fi.

A completed request that never received a response is a failure, not a successful load. Browsers never fire load with status === 0. This change makes __didCompleteResponse treat !error && status === 0 as an error, so onerror fires and fetch() rejects with the usual TypeError: Network request failed, which callers already handle.

This also hardens the iOS path: RCTNetworking.mm sends RCTNullIfNil(error.localizedDescription), so an error without a description currently reaches JS as a "success" as well.

Status 0 is safe as the signal: HTTP has no status 0, Android NetworkingModule custom URI handlers report 200, and RCTNetworking.mm reports 200 for non-HTTP NSURLResponses.

Related: #38625 (same RangeError via file://, closed for missing repro). The file:// case was later special-cased in whatwg-fetch, but any other status-0 completion still crashes.

Changelog:

[GENERAL] [FIXED] - XMLHttpRequest dispatches error instead of load when a request completes without ever receiving a response (status 0), preventing an uncatchable RangeError in fetch()

Test Plan:

• Added a unit test asserting that __didCompleteResponse(requestId, null) without a prior __didReceiveResponse dispatches error and loadend, not load.
• Updated the existing "should call onload function when there is no error" test to deliver a 200 response before completion, which is the only way a real request reaches load.
• Without the source change, the new test fails (load is dispatched with status === 0); with it, the suite passes.
• yarn jest packages/react-native/Libraries/Network/__tests__/XMLHttpRequest-test.js

 PASS  packages/react-native/Libraries/Network/__tests__/XMLHttpRequest-test.js
  XMLHttpRequest
    ✓ should transition readyState correctly (10 ms)
    ✓ should expose responseType correctly (14 ms)
    ✓ should expose responseText correctly (2 ms)
    ✓ should call ontimeout function when the request times out (1 ms)
    ✓ should call onerror function when the request times out (1 ms)
    ✓ should call onload function when there is no error (1 ms)
    ✓ should call onerror function when the request completes without a response (1 ms)
    ✓ should call upload onprogress (1 ms)
    ✓ should combine response headers with CRLF
    ✓ should log to a custom performance logger if set (1 ms)
    ✓ should append values when setRequestHeader is called with the same header
    ✓ should append to a header previously set to an empty string (2 ms)
    ✓ should lowercase header names in setRequestHeader
    ✓ should throw when setRequestHeader is called before open (1 ms)
    ✓ should sort and lowercase response headers

Test Suites: 1 passed, 1 total
Tests:       15 passed, 15 total
Snapshots:   0 total
Time:        0.31 s, estimated 1 s
Ran all test suites matching /packages\/react-native\/Libraries\/Network\/__tests__\/XMLHttpRequest-test.js/i.

• yarn flow: No errors. eslint --max-warnings 0 and prettier --check on both files pass.

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@fabriziocucci has imported this pull request. If you are a Meta employee, you can view this in D122990077.