[Flight] Dedupe modules

packages/react-noop-renderer/src/ReactNoopFlightServer.js

@@ -45,6 +45,9 @@ const ReactNoopFlightServer = ReactFlightServer({
   isModuleReference(reference: Object): boolean {
     return reference.$$typeof === Symbol.for('react.module.reference');
   },
+  getModuleKey(reference: Object): Object {
+    return reference;
+  },
   resolveModuleMetaData(
     config: void,
     reference: {$$typeof: Symbol, value: any},

packages/react-server/src/ReactFlightServer.js

@@ -14,6 +14,7 @@ import type {
   BundlerConfig,
   ModuleMetaData,
   ModuleReference,
+  ModuleKey,
 } from './ReactFlightServerConfig';
 
 import {
@@ -28,6 +29,7 @@ import {
   processSymbolChunk,
   processErrorChunk,
   resolveModuleMetaData,
+  getModuleKey,
   isModuleReference,
 } from './ReactFlightServerConfig';
 
@@ -79,6 +81,7 @@ export type Request = {
   completedJSONChunks: Array<Chunk>,
   completedErrorChunks: Array<Chunk>,
   writtenSymbols: Map<Symbol, number>,
+  writtenModules: Map<ModuleKey, number>,
   flowing: boolean,
   toJSON: (key: string, value: ReactModel) => ReactJSONValue,
 };
@@ -101,6 +104,7 @@ export function createRequest(
     completedJSONChunks: [],
     completedErrorChunks: [],
     writtenSymbols: new Map(),
+    writtenModules: new Map(),
     flowing: false,
     toJSON: function(key: string, value: ReactModel): ReactJSONValue {
       return resolveModelToJSON(request, this, key, value);
@@ -425,6 +429,11 @@ export function resolveModelToJSON(
   if (typeof value === 'object') {
     if (isModuleReference(value)) {
       const moduleReference: ModuleReference<any> = (value: any);
+      const moduleKey: ModuleKey = getModuleKey(moduleReference);
+      const existingId = request.writtenModules.get(moduleKey);
+      if (existingId !== undefined) {
+        return serializeByValueID(existingId);
+      }
       try {
         const moduleMetaData: ModuleMetaData = resolveModuleMetaData(
           request.bundlerConfig,

packages/react-server/src/ReactFlightServerBundlerConfigCustom.js

@@ -12,5 +12,7 @@ declare var $$$hostConfig: any;
 export opaque type BundlerConfig = mixed; // eslint-disable-line no-undef
 export opaque type ModuleReference<T> = mixed; // eslint-disable-line no-undef
 export opaque type ModuleMetaData: any = mixed; // eslint-disable-line no-undef
+export opaque type ModuleKey: any = mixed; // eslint-disable-line no-undef
 export const isModuleReference = $$$hostConfig.isModuleReference;
+export const getModuleKey = $$$hostConfig.getModuleKey;
 export const resolveModuleMetaData = $$$hostConfig.resolveModuleMetaData;

packages/react-transport-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js

@@ -38,6 +38,14 @@ export function isModuleReference(reference: Object): boolean {
   return reference instanceof JSResourceReference;
 }
 
+export type ModuleKey = ModuleReference<any>;
+
+export function getModuleKey(reference: ModuleReference<any>): ModuleKey {
+  // We use the reference object itself as the key because we assume the
+  // object will be cached by the bundler runtime.
+  return reference;
+}
+
 export function resolveModuleMetaData<T>(
   config: BundlerConfig,
   resource: ModuleReference<T>,

packages/react-transport-dom-webpack/src/ReactFlightServerWebpackBundlerConfig.js

@@ -25,8 +25,14 @@ export type ModuleMetaData = {
   name: string,
 };
 
+export type ModuleKey = string;
+
 const MODULE_TAG = Symbol.for('react.module.reference');
 
+export function getModuleKey(reference: ModuleReference<any>): ModuleKey {
+  return reference.name;
+}
+
 export function isModuleReference(reference: Object): boolean {
   return reference.$$typeof === MODULE_TAG;
 }

packages/react-transport-native-relay/src/ReactFlightNativeRelayServerHostConfig.js

@@ -38,6 +38,14 @@ export function isModuleReference(reference: Object): boolean {
   return reference instanceof JSResourceReferenceImpl;
 }
 
+export type ModuleKey = ModuleReference<any>;
+
+export function getModuleKey(reference: ModuleReference<any>): ModuleKey {
+  // We use the reference object itself as the key because we assume the
+  // object will be cached by the bundler runtime.
+  return reference;
+}
+
 export function resolveModuleMetaData<T>(
   config: BundlerConfig,
   resource: ModuleReference<T>,

scripts/jest/setupHostConfigs.js

@@ -35,6 +35,7 @@ jest.mock('react-server/flight', () => {
     jest.mock(shimServerFormatConfigPath, () => config);
     jest.mock('react-server/src/ReactFlightServerBundlerConfigCustom', () => ({
       isModuleReference: config.isModuleReference,
+      getModuleKey: config.getModuleKey,
       resolveModuleMetaData: config.resolveModuleMetaData,
     }));
     jest.mock(shimFlightServerConfigPath, () =>