[Flight] land enableHalt flag

enableHalt was added as a flag to experiment with a new semantic for prerendering RSC results. In particular we model RSC aborts for prerenders as unfinished streams where models awaiting a value will never get them. This sets the stage for resuming RSC renders in the future where we can expect a concategnation and continuation of the RSC result picking up the holes left by the aborted prerender. Prerender is already an unstable API and there is no future for the non-halting semantics so this commit lands the flag.

This change doesn't remove the flag entirely because halt semantics are also available while prerendering Fizz in the experimental channel. This API is not unstable and is more widely used so when we adopt the experimental behavior in a canary we should be closer to releasing the next major

Author: gnoff

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOM-test.js

@@ -62,21 +62,17 @@ describe('ReactFlightDOM', () => {
     jest.mock('react-server-dom-webpack/server', () =>
       require('react-server-dom-webpack/server.node.unbundled'),
     );
-    if (__EXPERIMENTAL__) {
-      jest.mock('react-server-dom-webpack/static', () =>
-        require('react-server-dom-webpack/static.node.unbundled'),
-      );
-    }
+    jest.mock('react-server-dom-webpack/static', () =>
+      require('react-server-dom-webpack/static.node.unbundled'),
+    );
     const WebpackMock = require('./utils/WebpackMock');
     clientExports = WebpackMock.clientExports;
     clientExportsESM = WebpackMock.clientExportsESM;
     clientModuleError = WebpackMock.clientModuleError;
     webpackMap = WebpackMock.webpackMap;
 
     ReactServerDOMServer = require('react-server-dom-webpack/server');
-    if (__EXPERIMENTAL__) {
-      ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
-    }
+    ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
 
     // This reset is to load modules for the SSR/Browser scope.
     jest.unmock('react-server-dom-webpack/server');
@@ -2771,7 +2767,6 @@ describe('ReactFlightDOM', () => {
     );
   });
 
-  // @gate experimental
   it('can prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {
@@ -2834,7 +2829,6 @@ describe('ReactFlightDOM', () => {
     expect(getMeaningfulChildren(container)).toEqual(<div>hello world</div>);
   });
 
-  // @gate enableHalt
   it('does not propagate abort reasons errors when aborting a prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {
@@ -2916,7 +2910,6 @@ describe('ReactFlightDOM', () => {
     expect(getMeaningfulChildren(container)).toEqual(<div>loading...</div>);
   });
 
-  // @gate enableHalt
   it('will leave async iterables in an incomplete state when halting', async () => {
     let resolve;
     const wait = new Promise(r => (resolve = r));
@@ -2976,7 +2969,6 @@ describe('ReactFlightDOM', () => {
     expect(await race).toBe('timeout');
   });
 
-  // @gate enableHalt
   it('will halt unfinished chunks inside Suspense when aborting a prerender', async () => {
     const controller = new AbortController();
     function ComponentThatAborts() {

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMBrowser-test.js

@@ -63,12 +63,10 @@ describe('ReactFlightDOMBrowser', () => {
     webpackMap = WebpackMock.webpackMap;
     webpackServerMap = WebpackMock.webpackServerMap;
     ReactServerDOMServer = require('react-server-dom-webpack/server');
-    if (__EXPERIMENTAL__) {
-      jest.mock('react-server-dom-webpack/static', () =>
-        require('react-server-dom-webpack/static.browser'),
-      );
-      ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
-    }
+    jest.mock('react-server-dom-webpack/static', () =>
+      require('react-server-dom-webpack/static.browser'),
+    );
+    ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
 
     __unmockReact();
     jest.resetModules();
@@ -2465,7 +2463,6 @@ describe('ReactFlightDOMBrowser', () => {
     expect(errors).toEqual([reason]);
   });
 
-  // @gate experimental
   it('can prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {
@@ -2514,7 +2511,6 @@ describe('ReactFlightDOMBrowser', () => {
     expect(container.innerHTML).toBe('<div>hello world</div>');
   });
 
-  // @gate enableHalt
   it('does not propagate abort reasons errors when aborting a prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMEdge-test.js

@@ -87,12 +87,10 @@ describe('ReactFlightDOMEdge', () => {
 
     ReactServer = require('react');
     ReactServerDOMServer = require('react-server-dom-webpack/server');
-    if (__EXPERIMENTAL__) {
-      jest.mock('react-server-dom-webpack/static', () =>
-        require('react-server-dom-webpack/static.edge'),
-      );
-      ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
-    }
+    jest.mock('react-server-dom-webpack/static', () =>
+      require('react-server-dom-webpack/static.edge'),
+    );
+    ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
 
     jest.resetModules();
     __unmockReact();
@@ -1291,7 +1289,6 @@ describe('ReactFlightDOMEdge', () => {
     ]);
   });
 
-  // @gate experimental
   it('can prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {
@@ -1345,7 +1342,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(result).toBe('<div>hello world</div>');
   });
 
-  // @gate enableHalt
   it('does not propagate abort reasons errors when aborting a prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {
@@ -1423,7 +1419,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(div.textContent).toBe('loading...');
   });
 
-  // @gate enableHalt
   it('should abort parsing an incomplete prerender payload', async () => {
     const infinitePromise = new Promise(() => {});
     const controller = new AbortController();
@@ -1471,7 +1466,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(error.message).toBe('Connection closed.');
   });
 
-  // @gate experimental
   it('should be able to handle a rejected promise in unstable_prerender', async () => {
     const expectedError = new Error('Bam!');
     const errors = [];
@@ -1510,7 +1504,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(error.message).toBe(expectedMessage);
   });
 
-  // @gate experimental
   it('should be able to handle an erroring async iterable in unstable_prerender', async () => {
     const expectedError = new Error('Bam!');
     const errors = [];
@@ -1557,7 +1550,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(error.message).toBe(expectedMessage);
   });
 
-  // @gate experimental
   it('should be able to handle an erroring readable stream in unstable_prerender', async () => {
     const expectedError = new Error('Bam!');
     const errors = [];
@@ -1605,7 +1597,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(error.message).toBe(expectedMessage);
   });
 
-  // @gate experimental
   it('can prerender an async iterable', async () => {
     const errors = [];
 
@@ -1649,7 +1640,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(text).toBe('hello world');
   });
 
-  // @gate experimental
   it('can prerender a readable stream', async () => {
     const errors = [];
 
@@ -1683,7 +1673,6 @@ describe('ReactFlightDOMEdge', () => {
     expect(result).toBe('hello world');
   });
 
-  // @gate experimental
   it('does not return a prerender prelude early when an error is emitted and there are still pending tasks', async () => {
     let rejectPromise;
     const rejectingPromise = new Promise(

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMNode-test.js

@@ -49,12 +49,10 @@ describe('ReactFlightDOMNode', () => {
     );
     ReactServer = require('react');
     ReactServerDOMServer = require('react-server-dom-webpack/server');
-    if (__EXPERIMENTAL__) {
-      jest.mock('react-server-dom-webpack/static', () =>
-        require('react-server-dom-webpack/static.node'),
-      );
-      ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
-    }
+    jest.mock('react-server-dom-webpack/static', () =>
+      require('react-server-dom-webpack/static.node'),
+    );
+    ReactServerDOMStaticServer = require('react-server-dom-webpack/static');
 
     const WebpackMock = require('./utils/WebpackMock');
     clientExports = WebpackMock.clientExports;
@@ -385,7 +383,6 @@ describe('ReactFlightDOMNode', () => {
     expect(errors).toEqual([reason]);
   });
 
-  // @gate experimental
   it('can prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {
@@ -440,7 +437,6 @@ describe('ReactFlightDOMNode', () => {
     expect(result).toBe('<div>hello world</div>');
   });
 
-  // @gate enableHalt
   it('does not propagate abort reasons errors when aborting a prerender', async () => {
     let resolveGreeting;
     const greetingPromise = new Promise(resolve => {

packages/react-server/src/ReactFlightServer.js

@@ -15,7 +15,6 @@ import type {TemporaryReferenceSet} from './ReactFlightServerTemporaryReferences
 
 import {
   enablePostpone,
-  enableHalt,
   enableTaint,
   enableProfilerTimer,
   enableComponentPerformanceTrack,
@@ -656,7 +655,7 @@ function serializeThenable(
         // We can no longer accept any resolved values
         request.abortableTasks.delete(newTask);
         newTask.status = ABORTED;
-        if (enableHalt && request.type === PRERENDER) {
+        if (request.type === PRERENDER) {
           request.pendingChunks--;
         } else {
           const errorId: number = (request.fatalError: any);
@@ -804,7 +803,7 @@ function serializeReadableStream(
     }
     aborted = true;
     request.abortListeners.delete(abortStream);
-    if (enableHalt && request.type === PRERENDER) {
+    if (request.type === PRERENDER) {
       request.pendingChunks--;
     } else {
       erroredTask(request, streamTask, reason);
@@ -930,7 +929,7 @@ function serializeAsyncIterable(
     }
     aborted = true;
     request.abortListeners.delete(abortIterable);
-    if (enableHalt && request.type === PRERENDER) {
+    if (request.type === PRERENDER) {
       request.pendingChunks--;
     } else {
       erroredTask(request, streamTask, reason);
@@ -2263,7 +2262,7 @@ function serializeBlob(request: Request, blob: Blob): string {
     }
     aborted = true;
     request.abortListeners.delete(abortBlob);
-    if (enableHalt && request.type === PRERENDER) {
+    if (request.type === PRERENDER) {
       request.pendingChunks--;
     } else {
       erroredTask(request, newTask, reason);
@@ -2318,7 +2317,7 @@ function renderModel(
 
     if (request.status === ABORTING) {
       task.status = ABORTED;
-      if (enableHalt && request.type === PRERENDER) {
+      if (request.type === PRERENDER) {
         // This will create a new task and refer to it in this slot
         // the new task won't be retried because we are aborting
         return outlineHaltedTask(request, task, wasReactNode);
@@ -4048,7 +4047,7 @@ function retryTask(request: Request, task: Task): void {
     if (request.status === ABORTING) {
       request.abortableTasks.delete(task);
       task.status = ABORTED;
-      if (enableHalt && request.type === PRERENDER) {
+      if (request.type === PRERENDER) {
         // When aborting a prerener with halt semantics we don't emit
         // anything into the slot for a task that aborts, it remains unresolved
         request.pendingChunks--;
@@ -4325,7 +4324,7 @@ export function abort(request: Request, reason: mixed): void {
     }
     const abortableTasks = request.abortableTasks;
     if (abortableTasks.size > 0) {
-      if (enableHalt && request.type === PRERENDER) {
+      if (request.type === PRERENDER) {
         // When prerendering with halt semantics we simply halt the task
         // and leave the reference unfulfilled.
         abortableTasks.forEach(task => haltTask(task, request));

packages/shared/ReactVersion.js

@@ -1,15 +1 @@
-/**
- * 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.
- */
-
-// TODO: this is special because it gets imported during build.
-//
-// It exists as a placeholder so that DevTools can support work tag changes between releases.
-// When we next publish a release, update the matching TODO in backend/renderer.js
-// TODO: This module is used both by the release scripts and to expose a version
-// at runtime. We should instead inject the version number as part of the build
-// process, and use the ReactVersions.js module as the single source of truth.
-export default '19.1.0';
+export default '19.2.0-canary-81f8be04-20250502';