feat: Cache Intl.* constructors

packages/next-intl/package.json

@@ -120,27 +120,27 @@
   "size-limit": [
     {
       "path": "dist/production/index.react-client.js",
-      "limit": "15.785 KB"
+      "limit": "16.055 KB"
     },
     {
       "path": "dist/production/index.react-server.js",
-      "limit": "16.66 KB"
+      "limit": "16.875 KB"
     },
     {
       "path": "dist/production/navigation.react-client.js",
       "limit": "3.465 KB"
     },
     {
       "path": "dist/production/navigation.react-server.js",
-      "limit": "18.075 KB"
+      "limit": "18.325 KB"
     },
     {
       "path": "dist/production/server.react-client.js",
       "limit": "1 KB"
     },
     {
       "path": "dist/production/server.react-server.js",
-      "limit": "15.84 KB"
+      "limit": "16.025 KB"
     },
     {
       "path": "dist/production/middleware.js",

packages/next-intl/src/react-server/getTranslator.tsx

@@ -10,7 +10,6 @@ import {
   createTranslator,
   MarkupTranslationValues
 } from 'use-intl/core';
-import {getMessageFormatCache} from '../shared/messageFormatCache';
 
 function getTranslatorImpl<
   NestedKey extends NamespaceKeys<
@@ -102,7 +101,6 @@ function getTranslatorImpl<
 } {
   return createTranslator({
     ...config,
-    messageFormatCache: getMessageFormatCache(),
     namespace
   });
 }

packages/next-intl/src/react-server/index.test.tsx

@@ -72,19 +72,27 @@ describe('performance', () => {
     expect(renderCount).toBe(3);
   });
 
-  it('shares message format cache between useTranslations and getTranslations', async () => {
+  it('shares a formatter cache between `useTranslations` and `getTranslations`', async () => {
     // First invocation
-    useTranslations('Component');
-    const firstCallCache =
-      vi.mocked(createTranslator).mock.calls[0][0].messageFormatCache;
+    // (simulate React rendering)
+    try {
+      useTranslations('Component');
+    } catch (promiseOrError) {
+      if (promiseOrError instanceof Promise) {
+        await promiseOrError;
+        useTranslations('Component');
+      } else {
+        throw promiseOrError;
+      }
+    }
 
     // Second invocation with a different namespace
     await getTranslations('Component2');
-    const secondCallCache =
-      vi.mocked(createTranslator).mock.calls[1][0].messageFormatCache;
 
-    // Verify that the same cache instance is used in both invocations
-    expect(firstCallCache).toBe(secondCallCache);
+    // Verify the cached formatters are shared
+    expect(vi.mocked(createTranslator).mock.calls[0][0]._formatters).toBe(
+      vi.mocked(createTranslator).mock.calls[1][0]._formatters
+    );
     expect(vi.mocked(createTranslator).mock.calls.length).toBe(2);
 
     vi.mocked(createTranslator).mockReset();

packages/next-intl/src/server/react-server/getConfig.tsx

@@ -1,5 +1,5 @@
 import {cache} from 'react';
-import {initializeConfig, IntlConfig} from 'use-intl/core';
+import {initializeConfig, IntlConfig, _createFormatters} from 'use-intl/core';
 import {getRequestLocale} from './RequestLocale';
 import createRequestConfig from './createRequestConfig';
 
@@ -52,19 +52,22 @@ async function receiveRuntimeConfigImpl(
 }
 const receiveRuntimeConfig = cache(receiveRuntimeConfigImpl);
 
+const getFormatters = cache(_createFormatters);
+
 async function getConfigImpl(localeOverride?: string): Promise<
   IntlConfig & {
     getMessageFallback: NonNullable<IntlConfig['getMessageFallback']>;
     now: NonNullable<IntlConfig['now']>;
     onError: NonNullable<IntlConfig['onError']>;
     timeZone: NonNullable<IntlConfig['timeZone']>;
+    _formatters: ReturnType<typeof _createFormatters>;
   }
 > {
   const runtimeConfig = await receiveRuntimeConfig(
     createRequestConfig,
     localeOverride
   );
-  return initializeConfig(runtimeConfig);
+  return {...initializeConfig(runtimeConfig), _formatters: getFormatters()};
 }
 const getConfig = cache(getConfigImpl);
 export default getConfig;

packages/next-intl/src/server/react-server/getTranslations.tsx

@@ -10,7 +10,6 @@ import {
   RichTranslationValues,
   MarkupTranslationValues
 } from 'use-intl/core';
-import {getMessageFormatCache} from '../../shared/messageFormatCache';
 import getConfig from './getConfig';
 
 // Maintainer note: `getTranslations` has two different call signatures.
@@ -215,7 +214,6 @@ async function getTranslations<
 
   return createTranslator({
     ...config,
-    messageFormatCache: getMessageFormatCache(),
     namespace,
     messages: config.messages
   });

packages/use-intl/.eslintrc.js

@@ -2,5 +2,13 @@ module.exports = {
   extends: ['molindo/typescript', 'molindo/react'],
   rules: {
     'import/no-useless-path-segments': 'error'
-  }
+  },
+  overrides: [
+    {
+      files: ['*.test.tsx'],
+      rules: {
+        'import/no-extraneous-dependencies': 'off'
+      }
+    }
+  ]
 };

packages/use-intl/package.json

@@ -63,6 +63,7 @@
     "formatting"
   ],
   "dependencies": {
+    "@formatjs/fast-memoize": "^2.2.0",
     "intl-messageformat": "^10.5.14"
   },
   "peerDependencies": {
@@ -83,14 +84,15 @@
     "react-dom": "^18.3.1",
     "rollup": "^4.18.0",
     "size-limit": "^8.2.6",
+    "tinyspy": "^3.0.0",
     "typescript": "^5.4.5",
     "vitest": "^1.6.0"
   },
   "prettier": "../../.prettierrc.json",
   "size-limit": [
     {
       "path": "dist/production/index.js",
-      "limit": "15.28 kB"
+      "limit": "15.545 kB"
     }
   ]
 }

packages/use-intl/src/core/createBaseTranslator.tsx

@@ -11,13 +11,13 @@ import AbstractIntlMessages from './AbstractIntlMessages';
 import Formats from './Formats';
 import {InitializedIntlConfig} from './IntlConfig';
 import IntlError, {IntlErrorCode} from './IntlError';
-import MessageFormatCache from './MessageFormatCache';
 import TranslationValues, {
   MarkupTranslationValues,
   RichTranslationValues
 } from './TranslationValues';
 import convertFormatsToIntlMessageFormat from './convertFormatsToIntlMessageFormat';
 import {defaultGetMessageFallback, defaultOnError} from './defaults';
+import {Formatters} from './formatters';
 import joinPath from './joinPath';
 import MessageKeys from './utils/MessageKeys';
 import NestedKeyOf from './utils/NestedKeyOf';
@@ -125,7 +125,7 @@ function getMessagesOrError<Messages extends AbstractIntlMessages>(
 }
 
 export type CreateBaseTranslatorProps<Messages> = InitializedIntlConfig & {
-  messageFormatCache?: MessageFormatCache;
+  formatters: Formatters;
   defaultTranslationValues?: RichTranslationValues;
   namespace?: string;
   messagesOrError: Messages | IntlError;
@@ -171,9 +171,9 @@ function createBaseTranslatorImpl<
 >({
   defaultTranslationValues,
   formats: globalFormats,
+  formatters,
   getMessageFallback = defaultGetMessageFallback,
   locale,
-  messageFormatCache,
   messagesOrError,
   namespace,
   onError,
@@ -218,81 +218,69 @@ function createBaseTranslatorImpl<
       );
     }
 
-    const cacheKey = joinPath(locale, namespace, key, String(message));
+    if (typeof message === 'object') {
+      let code, errorMessage;
+      if (Array.isArray(message)) {
+        code = IntlErrorCode.INVALID_MESSAGE;
+        if (process.env.NODE_ENV !== 'production') {
+          errorMessage = `Message at \`${joinPath(
+            namespace,
+            key
+          )}\` resolved to an array, but only strings are supported. See https://next-intl-docs.vercel.app/docs/usage/messages#arrays-of-messages`;
+        }
+      } else {
+        code = IntlErrorCode.INSUFFICIENT_PATH;
+        if (process.env.NODE_ENV !== 'production') {
+          errorMessage = `Message at \`${joinPath(
+            namespace,
+            key
+          )}\` resolved to an object, but only strings are supported. Use a \`.\` to retrieve nested messages. See https://next-intl-docs.vercel.app/docs/usage/messages#structuring-messages`;
+        }
+      }
+
+      return getFallbackFromErrorAndNotify(key, code, errorMessage);
+    }
 
     let messageFormat: IntlMessageFormat;
-    if (messageFormatCache?.has(cacheKey)) {
-      messageFormat = messageFormatCache.get(cacheKey)!;
-    } else {
-      if (typeof message === 'object') {
-        let code, errorMessage;
-        if (Array.isArray(message)) {
-          code = IntlErrorCode.INVALID_MESSAGE;
-          if (process.env.NODE_ENV !== 'production') {
-            errorMessage = `Message at \`${joinPath(
-              namespace,
-              key
-            )}\` resolved to an array, but only strings are supported. See https://next-intl-docs.vercel.app/docs/usage/messages#arrays-of-messages`;
-          }
-        } else {
-          code = IntlErrorCode.INSUFFICIENT_PATH;
-          if (process.env.NODE_ENV !== 'production') {
-            errorMessage = `Message at \`${joinPath(
-              namespace,
-              key
-            )}\` resolved to an object, but only strings are supported. Use a \`.\` to retrieve nested messages. See https://next-intl-docs.vercel.app/docs/usage/messages#structuring-messages`;
-          }
-        }
 
-        return getFallbackFromErrorAndNotify(key, code, errorMessage);
-      }
+    // Hot path that avoids creating an `IntlMessageFormat` instance
+    const plainMessage = getPlainMessage(message as string, values);
+    if (plainMessage) return plainMessage;
 
-      // Hot path that avoids creating an `IntlMessageFormat` instance
-      const plainMessage = getPlainMessage(message as string, values);
-      if (plainMessage) return plainMessage;
-
-      try {
-        messageFormat = new IntlMessageFormat(
-          message,
-          locale,
-          convertFormatsToIntlMessageFormat(
-            {...globalFormats, ...formats},
-            timeZone
-          ),
-          {
-            formatters: {
-              getNumberFormat(locales, options) {
-                return new Intl.NumberFormat(
-                  locales,
-                  // `useGrouping` was changed from a boolean later to a string enum or boolean, the type definition is outdated (https://tc39.es/proposal-intl-numberformat-v3/#grouping-enum-ecma-402-367)
-                  options as Intl.NumberFormatOptions
-                );
-              },
-              getDateTimeFormat(locales, options) {
-                // Workaround for https://github.com/formatjs/formatjs/issues/4279
-                return new Intl.DateTimeFormat(locales, {timeZone, ...options});
-              },
-              getPluralRules(locales, options) {
-                return new Intl.PluralRules(locales, options);
-              }
+    try {
+      messageFormat = formatters.getMessageFormat(
+        message,
+        locale,
+        convertFormatsToIntlMessageFormat(
+          {...globalFormats, ...formats},
+          timeZone
+        ),
+        {
+          // @ts-expect-error -- TS is currently lacking support for ECMA-402 10.0 (`useGrouping: 'auto'`, see https://github.com/microsoft/TypeScript/issues/56269)
+          formatters: {
+            ...formatters,
+            getDateTimeFormat(locales, options) {
+              // Workaround for https://github.com/formatjs/formatjs/issues/4279
+              return formatters.getDateTimeFormat(locales, {
+                timeZone,
+                ...options
+              });
             }
           }
-        );
-      } catch (error) {
-        const thrownError = error as Error;
-        return getFallbackFromErrorAndNotify(
-          key,
-          IntlErrorCode.INVALID_MESSAGE,
-          process.env.NODE_ENV !== 'production'
-            ? thrownError.message +
-                ('originalMessage' in thrownError
-                  ? ` (${thrownError.originalMessage})`
-                  : '')
-            : thrownError.message
-        );
-      }
-
-      messageFormatCache?.set(cacheKey, messageFormat);
+        }
+      );
+    } catch (error) {
+      const thrownError = error as Error;
+      return getFallbackFromErrorAndNotify(
+        key,
+        IntlErrorCode.INVALID_MESSAGE,
+        process.env.NODE_ENV !== 'production'
+          ? thrownError.message +
+              ('originalMessage' in thrownError
+                ? ` (${thrownError.originalMessage})`
+                : '')
+          : thrownError.message
+      );
     }
 
     try {