Add Fantom WPT conformance harness (#58267)

.github/actions/run-fantom-tests/action.yml

@@ -14,6 +14,28 @@ runs:
       uses: ./.github/actions/setup-node
     - name: Install node dependencies
       uses: ./.github/actions/yarn-install
+    - name: Read WPT revision
+      id: wpt-revision
+      shell: bash
+      run: |
+        echo "revision=$(node -e 'process.stdout.write(require("./scripts/web-platform-tests/sync").WPT_REVISION)')" >> "$GITHUB_OUTPUT"
+    - name: Checkout WPT
+      uses: actions/checkout@v6
+      with:
+        repository: web-platform-tests/wpt
+        ref: ${{ steps.wpt-revision.outputs.revision }}
+        path: .wpt
+        sparse-checkout: |
+          fetch
+          resources
+          streams
+          tools
+          wpt
+    - name: Generate WPT fixtures
+      shell: bash
+      run: |
+        ./.wpt/wpt manifest --no-download --rebuild fetch streams
+        yarn sync-wpt --wpt-root="$GITHUB_WORKSPACE/.wpt"
     - name: Download Fantom Runner binary
       uses: actions/download-artifact@v7
       with:

.gitignore

@@ -170,9 +170,11 @@ fix_*.patch
 .metro-health-check*
 
 # Jest Integration
+/.wpt/
 /private/react-native-fantom/build/
 /private/react-native-fantom/.out/
 /private/react-native-fantom/tester/build/
+/packages/react-native/src/private/webapis/__tests__/wpt/generated/
 
 # [Experimental] Generated TS type definitions
 /packages/**/types_generated/

.prettierignore

@@ -10,3 +10,5 @@ vendor
 packages/**/types_generated/
 
 packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeEnumTurboModule.js
+packages/react-native/src/private/webapis/__tests__/wpt/generated/wpt-fixtures.json
+packages/react-native/src/private/webapis/__tests__/wpt/wpt-baseline.json

package.json

@@ -35,9 +35,12 @@
     "test-ios": "./scripts/objc-test.sh test",
     "test-typescript-legacy": "tsc -p packages/react-native/__typetests__/tsconfig.legacy.json",
     "test-generated-typescript": "tsc -p packages/react-native/__typetests__/tsconfig.json",
+    "test-wpt": "yarn fantom 'WPT(Fetch|Streams)-itest'",
     "test": "jest",
     "fantom": "./scripts/fantom.sh",
     "fantom-cli": "./scripts/fantom-cli.sh",
+    "sync-wpt": "node ./scripts/web-platform-tests/sync.js",
+    "update-wpt-baseline": "node ./scripts/web-platform-tests/update-baseline.js",
     "trigger-react-native-release": "node ./scripts/releases-local/trigger-react-native-release.js",
     "update-lock": "npx yarn-deduplicate"
   },

packages/react-native/src/private/webapis/__tests__/wpt/README.md

@@ -0,0 +1,103 @@
+# Web Platform Tests for Fetch and Streams
+
+These tests run the shell-compatible portions of the upstream Web Platform
+Tests (WPT) `fetch/` and `streams/` suites inside React Native's Fantom runtime.
+The committed `wpt-baseline.json` results are an expectation baseline: both an
+unexpected failure and an unexpected pass fail CI until the baseline is
+deliberately updated.
+
+The fixtures are generated on demand and are not committed. They are pinned to
+the WPT revision named by `WPT_REVISION` in
+`scripts/web-platform-tests/sync.js` and contain byte-for-byte copies of the
+upstream test sources, their `// META: script` dependencies, and WPT's
+`testharness.js`. WPT is distributed under the
+[3-Clause BSD License](https://github.com/web-platform-tests/wpt/blob/master/LICENSE.md).
+The runner recognizes a `test(() => {}, ...)` registration without changing
+its source so that assertion-free markers remain excluded from conformance
+counts. The current expected results live in `wpt-baseline.json`; the generated
+fixture also records every test file excluded by the environment boundary and
+its reason.
+
+Selection is derived from WPT's `MANIFEST.json`, not from a file allowlist. A
+source is runnable when the manifest classifies it as a `testharness` `.any.js`
+test with a dedicated-worker variant and its declared scripts and reachable
+host APIs are available in Fantom. Unsupported records include the manifest
+type, generated URLs, declared globals/scripts, and the detected requirement.
+
+## Running the suites
+
+From the React Native repository root:
+
+```shell
+yarn test-wpt
+```
+
+Fantom `-itest.js` files are part of the existing Fantom CI job, so the GitHub
+Actions job checks out the pinned WPT revision, generates the fixture, and then
+runs these suites. The CI tests execute the files in a deterministic shuffled
+order and compare them with a baseline captured in manifest order. This makes
+an order-dependent result fail the suite.
+
+An expected result can be changed to `FLAKY` in the baseline when it is known to
+be intermittent. A flaky result accepts either a pass or a failure in CI, and
+the baseline updater carries the `FLAKY` status forward by file, test name, and
+duplicate-name occurrence. It must be removed manually once the test is stable.
+
+When a suite has no conformance passes and every ordinary subtest failure names
+a runtime global that is actually absent, the result is reported as `BLOCKED`.
+The baseline records the dominant missing global, all missing globals, and the
+number of gated files and subtests instead of retaining hundreds of equivalent
+failure rows. Harness-generated failures such as file-evaluation errors remain
+visible separately.
+
+## Updating WPT and the baseline
+
+1. Obtain a checkout of
+   [web-platform-tests/wpt](https://github.com/web-platform-tests/wpt) at the
+   revision named by `WPT_REVISION` in
+   `scripts/web-platform-tests/sync.js`. To move to a newer upstream revision,
+   update that constant first.
+2. Generate WPT's manifest at that revision:
+
+   ```shell
+   ./wpt manifest --no-download --rebuild fetch streams
+   ```
+
+3. Regenerate the local fixture:
+
+   ```shell
+   yarn sync-wpt --wpt-root=/absolute/path/to/wpt
+   ```
+
+   The fixture is ignored by Git. The generator verifies the checkout revision
+   and every selected or excluded test source against its manifest Git-blob
+   hash.
+4. Review the manifest-derived runnable and unsupported inventory in the
+   generated fixture. If the environment capability rules have changed, update
+   the classifier in `sync.js`.
+5. Record current React Native behavior and verify the new baseline:
+
+   ```shell
+   yarn update-wpt-baseline
+   ```
+
+6. Review every changed result before accepting the new baseline. The update
+   command preserves existing `FLAKY` statuses and reruns `yarn test-wpt`
+   against the newly written baseline.
+
+## Environment limitations
+
+Fantom supplies React Native's real JavaScript globals and Hermes runtime, but
+its HTTP client is intentionally a non-completing stub. Fetch tests that require
+the WPT HTTP(S) server therefore cannot run without changing the Fantom native
+test environment. Browser-only tests also cannot run because Fantom has no DOM,
+navigation, Window, service worker, or shared worker environment.
+
+The Streams suite runs `.any.js` tests that are compatible with a JavaScript
+shell. WebIDL harness tests, explicit garbage-collection tests, and tests that
+require browser transferables such as `MessagePort` or `VideoFrame` are recorded
+as unsupported in the generated fixture.
+
+The adapter processes direct `// META: script=` dependencies. Other WPT
+execution metadata, nested dependency metadata, and browser or worker realm
+creation are not implemented.

packages/react-native/src/private/webapis/__tests__/wpt/WPTBaseline.js

@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {WPTSuiteResult} from './WPTTestHarness';
+
+export type WPTBaseline = {
+  fetch: WPTSuiteResult,
+  streams: WPTSuiteResult,
+};
+
+// $FlowExpectedError[untyped-import] JSON cannot carry a Flow declaration.
+const baseline = require('./wpt-baseline.json') as WPTBaseline;
+
+export default baseline;

packages/react-native/src/private/webapis/__tests__/wpt/WPTBaselineCapture.js

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import '@react-native/fantom/src/setUpDefaultReactNativeEnvironment';
+
+import baseline from './WPTBaseline';
+import fixtures from './WPTFixtures';
+import {applyWPTFlakyStatuses, runWPTSuite} from './WPTTestHarness';
+
+const BASELINE_MARKER = '__RN_WPT_BASELINE__';
+describe('Web Platform Tests baseline capture', () => {
+  it('captures fetch', () => {
+    const result = applyWPTFlakyStatuses(
+      runWPTSuite(fixtures, 'fetch'),
+      baseline.fetch,
+    );
+    console.log(`${BASELINE_MARKER}fetch:${JSON.stringify(result)}`);
+  });
+
+  it('captures streams', () => {
+    const result = applyWPTFlakyStatuses(
+      runWPTSuite(fixtures, 'streams'),
+      baseline.streams,
+    );
+    console.log(`${BASELINE_MARKER}streams:${JSON.stringify(result)}`);
+  });
+});

packages/react-native/src/private/webapis/__tests__/wpt/WPTFetch-itest.js

@@ -0,0 +1,74 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {WPTSuiteResult} from './WPTTestHarness';
+
+import baseline from './WPTBaseline';
+import fixtures from './WPTFixtures';
+import {
+  applyWPTFlakyStatuses,
+  getWPTExecutionPaths,
+  runWPTSuite,
+} from './WPTTestHarness';
+
+import '@react-native/fantom/src/setUpDefaultReactNativeEnvironment';
+
+function singleTestResult(status: string): WPTSuiteResult {
+  return {
+    files: [
+      {
+        harnessStatus: 'OK',
+        path: 'example.any.js',
+        tests: [{name: 'intermittent result', status}],
+      },
+    ],
+    manifest: {sha256: 'test', version: 0},
+    revision: 'test',
+    source: 'test',
+    suite: 'fetch',
+    summary: {
+      BLOCKED: 0,
+      FAIL: status === 'FAIL' ? 1 : 0,
+      FLAKY: status === 'FLAKY' ? 1 : 0,
+      NOTRUN: 0,
+      PASS: status === 'PASS' ? 1 : 0,
+      PRECONDITION_FAILED: 0,
+      TIMEOUT: 0,
+      noOpTests: 0,
+      total: 1,
+      unsupportedFiles: 0,
+    },
+  };
+}
+
+describe('Web Platform Tests: fetch', () => {
+  it('uses a non-manifest deterministic order', () => {
+    expect(
+      getWPTExecutionPaths(fixtures, 'fetch', 'deterministic-shuffle'),
+    ).not.toEqual(getWPTExecutionPaths(fixtures, 'fetch', 'manifest'));
+  });
+
+  it('matches the manifest-order baseline when shuffled', () => {
+    const result = runWPTSuite(fixtures, 'fetch', 'deterministic-shuffle');
+    expect(applyWPTFlakyStatuses(result, baseline.fetch)).toEqual(
+      baseline.fetch,
+    );
+  });
+
+  it('preserves a flaky baseline result for either outcome', () => {
+    const flakyBaseline = singleTestResult('FLAKY');
+    expect(
+      applyWPTFlakyStatuses(singleTestResult('PASS'), flakyBaseline),
+    ).toEqual(flakyBaseline);
+    expect(
+      applyWPTFlakyStatuses(singleTestResult('FAIL'), flakyBaseline),
+    ).toEqual(flakyBaseline);
+  });
+});

packages/react-native/src/private/webapis/__tests__/wpt/WPTFixtures.js

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {WPTFixtures} from './WPTTestHarness';
+
+let fixtures: WPTFixtures;
+try {
+  // $FlowExpectedError[untyped-import] JSON cannot carry a Flow declaration.
+  // $FlowExpectedError[cannot-resolve-module] Generated by sync.js, not committed.
+  fixtures = require('./generated/wpt-fixtures.json') as WPTFixtures;
+} catch {
+  throw new Error(
+    'wpt-fixtures.json not found. Run: node scripts/web-platform-tests/sync.js --wpt-root=/path/to/wpt',
+  );
+}
+
+export default fixtures;

packages/react-native/src/private/webapis/__tests__/wpt/WPTStreams-itest.js

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import '@react-native/fantom/src/setUpDefaultReactNativeEnvironment';
+
+import baseline from './WPTBaseline';
+import fixtures from './WPTFixtures';
+import {
+  applyWPTFlakyStatuses,
+  getWPTExecutionPaths,
+  runWPTSuite,
+} from './WPTTestHarness';
+
+describe('Web Platform Tests: streams', () => {
+  it('uses a non-manifest deterministic order', () => {
+    expect(
+      getWPTExecutionPaths(fixtures, 'streams', 'deterministic-shuffle'),
+    ).not.toEqual(getWPTExecutionPaths(fixtures, 'streams', 'manifest'));
+  });
+
+  it('matches the manifest-order baseline when shuffled', () => {
+    const result = runWPTSuite(fixtures, 'streams', 'deterministic-shuffle');
+    expect(applyWPTFlakyStatuses(result, baseline.streams)).toEqual(
+      baseline.streams,
+    );
+  });
+});