Cache

facebook · sebmarkbage · Oct 23, 2022 · Oct 23, 2022 · Oct 23, 2022 · Oct 23, 2022
commit db586ec8d17be380b3dfbe5607f6ec58c2ede235
diff --git a/packages/react-server/src/ReactFlightServer.js b/packages/react-server/src/ReactFlightServer.js
@@ -43,6 +43,8 @@ import {
   resolveModuleMetaData,
   getModuleKey,
   isModuleReference,
+  supportsRequestStorage,
+  requestStorage,
 } from './ReactFlightServerConfig';
 
 import {
@@ -157,6 +159,16 @@ export function createRequest(
   context?: Array<[string, ServerContextJSONValue]>,
   identifierPrefix?: string,
 ): Request {
+  if (
+    ReactCurrentCache.current !== null &&
+    ReactCurrentCache.current !== DefaultCacheDispatcher
+  ) {
+    throw new Error(
+      'Currently React only supports one RSC renderer at a time.',
+    );
+  }
+  ReactCurrentCache.current = DefaultCacheDispatcher;
+
   const abortSet: Set<Task> = new Set();
   const pingedTasks = [];
   const request = {
@@ -1155,10 +1167,8 @@ function retryTask(request: Request, task: Task): void {
 
 function performWork(request: Request): void {
   const prevDispatcher = ReactCurrentDispatcher.current;
-  const prevCacheDispatcher = ReactCurrentCache.current;
   const prevCache = getCurrentCache();
   ReactCurrentDispatcher.current = HooksDispatcher;
-  ReactCurrentCache.current = DefaultCacheDispatcher;
   setCurrentCache(request.cache);
   prepareToUseHooksForRequest(request);
 
@@ -1177,7 +1187,6 @@ function performWork(request: Request): void {
     fatalError(request, error);
   } finally {
     ReactCurrentDispatcher.current = prevDispatcher;
-    ReactCurrentCache.current = prevCacheDispatcher;
     setCurrentCache(prevCache);
     resetHooksForRequest();
   }

diff --git a/packages/react-server/src/ReactFlightServerConfigStream.js b/packages/react-server/src/ReactFlightServerConfigStream.js
@@ -72,6 +72,11 @@ import type {Chunk} from './ReactServerStreamConfig';
 
 export type {Destination, Chunk} from './ReactServerStreamConfig';
 
+export {
+  supportsRequestStorage,
+  requestStorage,
+} from './ReactServerStreamConfig';
+
 const stringify = JSON.stringify;
 
 function serializeRowHeader(tag: string, id: number) {

diff --git a/packages/react-server/src/ReactServerStreamConfigBrowser.js b/packages/react-server/src/ReactServerStreamConfigBrowser.js
@@ -21,6 +21,11 @@ export function flushBuffered(destination: Destination) {
   // transform streams. https://github.com/whatwg/streams/issues/960
 }
 
+// For now we support AsyncLocalStorage as a global for the "browser" builds
+// TODO: Move this to some special WinterCG build.
+export const supportsRequestStorage = typeof AsyncLocalStorage === 'function';
+export const requestStorage = new AsyncLocalStorage();
+
 const VIEW_SIZE = 512;
 let currentView = null;
 let writtenBytes = 0;

diff --git a/packages/react-server/src/ReactServerStreamConfigNode.js b/packages/react-server/src/ReactServerStreamConfigNode.js
@@ -9,6 +9,7 @@
 
 import type {Writable} from 'stream';
 import {TextEncoder} from 'util';
+import {AsyncLocalStorage} from 'async_hooks';
 
 interface MightBeFlushable {
   flush?: () => void;
@@ -33,6 +34,9 @@ export function flushBuffered(destination: Destination) {
   }
 }
 
+export const supportsRequestStorage = true;
+export const requestStorage = new AsyncLocalStorage();
+
 const VIEW_SIZE = 2048;
 let currentView = null;
 let writtenBytes = 0;

diff --git a/packages/react/src/__tests__/ReactFetch-test.js b/packages/react/src/__tests__/ReactFetch-test.js
@@ -76,6 +76,22 @@ describe('ReactFetch', () => {
     expect(fetchCount).toBe(1);
   });
 
+  // @gate enableFetchInstrumentation && enableCache
+  it('can dedupe fetches in micro tasks', async () => {
+    async function getData() {
+      const r1 = await fetch('hello');
+      const t1 = await r1.text();
+      const r2 = await fetch('hello');
+      const t2 = await r2.text();
+      return t1 + ' ' + t2;
+    }
+    function Component() {
+      return use(getData());
+    }
+    expect(await render(Component)).toMatchInlineSnapshot(`"GET world []"`);
+    expect(fetchCount).toBe(2);
+  });
+
   // @gate enableFetchInstrumentation && enableCache
   it('can dedupe fetches using Request and not', async () => {
     function Component() {

diff --git a/scripts/error-codes/codes.json b/scripts/error-codes/codes.json
@@ -442,5 +442,6 @@
   "454": "React expected a <body> element (document.body) to exist in the Document but one was not found. React never removes the body for any Document it renders into so the cause is likely in some other script running on this page.",
   "455": "This CacheSignal was requested outside React which means that it is immediately aborted.",
   "456": "Calling Offscreen.detach before instance handle has been set.",
-  "457": "acquireHeadResource encountered a resource type it did not expect: \"%s\". This is a bug in React."
+  "457": "acquireHeadResource encountered a resource type it did not expect: \"%s\". This is a bug in React.",
+  "458": "Currently React only supports one RSC renderer at a time"
 }
diff --git a/scripts/rollup/bundles.js b/scripts/rollup/bundles.js
@@ -320,7 +320,7 @@ const bundles = [
     global: 'ReactDOMServer',
     minifyWithProdErrorCodes: false,
     wrapWithModuleBoundaries: false,
-    externals: ['react', 'util', 'react-dom'],
+    externals: ['react', 'util', 'async-hooks', 'react-dom'],
   },
   {
     bundleTypes: __EXPERIMENTAL__ ? [FB_WWW_DEV, FB_WWW_PROD] : [],
@@ -394,7 +394,7 @@ const bundles = [
     global: 'ReactServerDOMServer',
     minifyWithProdErrorCodes: false,
     wrapWithModuleBoundaries: false,
-    externals: ['react', 'util', 'react-dom'],
+    externals: ['react', 'util', 'async-hooks', 'react-dom'],
   },
 
   /******* React Server DOM Webpack Client *******/