fix(core): optimize i18n integration for site builds + improve inference of locale config

.github/workflows/tests-e2e.yml

@@ -38,7 +38,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: ['20.0', '20', '22', '24', '25']
+        node: ['20.0', '20', '22', '24', '25.1']
     steps:
       - name: Checkout
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0

.github/workflows/tests-windows.yml

@@ -27,7 +27,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        node: ['20.0', '20', '22', '24', '25']
+        node: ['20.0', '20', '22', '24', '25.1']
     steps:
       - name: Support longpaths
         run: git config --system core.longpaths true

.github/workflows/tests.yml

@@ -27,7 +27,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: ['20.0', '20', '22', '24', '25']
+        node: ['20.0', '20', '22', '24', '25.1']
     steps:
       - name: Checkout
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0

.prettierignore

@@ -1,7 +1,7 @@
 dist
 node_modules
 .yarn
-build
+**/build/**
 coverage
 .docusaurus
 .idea
@@ -11,6 +11,8 @@ coverage
 
 jest/vendor
 
+argos/test-results
+
 packages/lqip-loader/lib/
 packages/docusaurus/lib/
 packages/docusaurus-*/lib/*

packages/docusaurus/src/commands/build/build.ts

@@ -8,10 +8,10 @@
 import fs from 'fs-extra';
 import logger, {PerfLogger} from '@docusaurus/logger';
 import {mapAsyncSequential} from '@docusaurus/utils';
-import {loadContext, type LoadContextParams} from '../../server/site';
-import {loadI18n} from '../../server/i18n';
+import {type LoadContextParams} from '../../server/site';
+import {loadI18nLocaleList} from '../../server/i18n';
 import {buildLocale, type BuildLocaleParams} from './buildLocale';
-import {isAutomaticBaseUrlLocalizationDisabled} from './buildUtils';
+import {loadSiteConfig} from '../../server/config';
 
 export type BuildCLIOptions = Pick<LoadContextParams, 'config' | 'outDir'> & {
   locale?: [string, ...string[]];
@@ -81,27 +81,21 @@ async function getLocalesToBuild({
   siteDir: string;
   cliOptions: BuildCLIOptions;
 }): Promise<[string, ...string[]]> {
-  // TODO we shouldn't need to load all context + i18n just to get that list
-  // only loading siteConfig should be enough
-  const context = await loadContext({
+  const {siteConfig} = await loadSiteConfig({
     siteDir,
-    outDir: cliOptions.outDir,
-    config: cliOptions.config,
-    automaticBaseUrlLocalizationDisabled: isAutomaticBaseUrlLocalizationDisabled(cliOptions),
+    customConfigFilePath: cliOptions.config,
   });
 
-  const i18n = await loadI18n({
-    siteDir,
-    config: context.siteConfig,
-    currentLocale: context.siteConfig.i18n.defaultLocale, // Awkward but ok
-    automaticBaseUrlLocalizationDisabled: false,
-  });
-
-  const locales = cliOptions.locale ?? i18n.locales;
+  const locales =
+    cliOptions.locale ??
+    loadI18nLocaleList({
+      i18nConfig: siteConfig.i18n,
+      currentLocale: siteConfig.i18n.defaultLocale, // Awkward but ok
+    });
 
   return orderLocales({
     locales: locales as [string, ...string[]],
-    defaultLocale: i18n.defaultLocale,
+    defaultLocale: siteConfig.i18n.defaultLocale,
   });
 }
 

packages/docusaurus/src/server/__tests__/i18n.test.ts

@@ -123,9 +123,11 @@ describe('defaultLocaleConfig', () => {
 });
 
 describe('loadI18n', () => {
-  const consoleSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+  const consoleWarnSpy = jest
+    .spyOn(console, 'warn')
+    .mockImplementation(() => {});
   beforeEach(() => {
-    consoleSpy.mockClear();
+    consoleWarnSpy.mockClear();
   });
 
   it('loads I18n for default config', async () => {
@@ -397,8 +399,67 @@ describe('loadI18n', () => {
       },
       currentLocale: 'it',
     });
-    expect(consoleSpy.mock.calls[0]![0]).toMatch(
-      /The locale .*it.* was not found in your site configuration/,
+    expect(consoleWarnSpy.mock.calls[0]![0]).toMatch(
+      /The locale .*it.* was not found in your Docusaurus site configuration/,
     );
   });
+
+  it('throws when trying to load undeclared locale that is not a valid locale BCP47 name', async () => {
+    await expect(() =>
+      loadI18nTest({
+        i18nConfig: {
+          path: 'i18n',
+          defaultLocale: 'en',
+          locales: ['en', 'fr', 'de'],
+          localeConfigs: {},
+        },
+        currentLocale: 'x1',
+      }),
+    ).rejects.toThrowErrorMatchingInlineSnapshot(`
+      "Docusaurus couldn't infer a default locale config for x1.
+      Make sure it is a valid BCP 47 locale name (e.g. en, fr, fr-FR, etc.) and/or provide a valid BCP 47 \`siteConfig.i18n.localeConfig['x1'].htmlLang\` attribute."
+    `);
+  });
+
+  it('throws when trying to load declared locale that is not a valid locale BCP47 name', async () => {
+    await expect(() =>
+      loadI18nTest({
+        i18nConfig: {
+          path: 'i18n',
+          defaultLocale: 'fr',
+          locales: ['en', 'fr', 'de'],
+          localeConfigs: {x1: {}},
+        },
+        currentLocale: 'x1',
+      }),
+    ).rejects.toThrowErrorMatchingInlineSnapshot(`
+      "Docusaurus couldn't infer a default locale config for x1.
+      Make sure it is a valid BCP 47 locale name (e.g. en, fr, fr-FR, etc.) and/or provide a valid BCP 47 \`siteConfig.i18n.localeConfig['x1'].htmlLang\` attribute."
+    `);
+  });
+
+  it('loads i18n when trying to load declared locale with invalid BCP47 name but valid BCP47', async () => {
+    const result = await loadI18nTest({
+      i18nConfig: {
+        path: 'i18n',
+        defaultLocale: 'en',
+        locales: ['en', 'fr', 'x1'],
+        localeConfigs: {
+          x1: {htmlLang: 'en-US'},
+        },
+      },
+      currentLocale: 'x1',
+    });
+    expect(result.localeConfigs.x1).toEqual({
+      baseUrl: '/x1/',
+      calendar: 'gregory',
+      direction: 'ltr',
+      htmlLang: 'en-US',
+      label: 'American English',
+      path: 'en-US',
+      translate: false,
+      url: 'https://example.com',
+    });
+    expect(consoleWarnSpy).toHaveBeenCalledTimes(0);
+  });
 });

packages/docusaurus/src/server/i18n.ts

@@ -10,7 +10,12 @@ import fs from 'fs-extra';
 import logger from '@docusaurus/logger';
 import combinePromises from 'combine-promises';
 import {normalizeUrl} from '@docusaurus/utils';
-import type {I18n, DocusaurusConfig, I18nLocaleConfig} from '@docusaurus/types';
+import type {
+  I18n,
+  DocusaurusConfig,
+  I18nLocaleConfig,
+  I18nConfig,
+} from '@docusaurus/types';
 
 function inferLanguageDisplayName(locale: string) {
   const tryLocale = (l: string) => {
@@ -95,12 +100,33 @@ export function getDefaultLocaleConfig(
     };
   } catch (e) {
     throw new Error(
-      `Docusaurus couldn't get default locale config for ${locale}`,
+      `Docusaurus couldn't infer a default locale config for ${logger.name(
+        locale,
+      )}.
+Make sure it is a valid BCP 47 locale name (e.g. en, fr, fr-FR, etc.) and/or provide a valid BCP 47 ${logger.code(
+        `siteConfig.i18n.localeConfig['${locale}'].htmlLang`,
+      )} attribute.`,
       {cause: e},
     );
   }
 }
 
+export function loadI18nLocaleList({
+  i18nConfig,
+  currentLocale,
+}: {
+  i18nConfig: I18nConfig;
+  currentLocale: string;
+}): [string, ...string[]] {
+  if (!i18nConfig.locales.includes(currentLocale)) {
+    logger.warn`The locale name=${currentLocale} was not found in your Docusaurus site configuration.
+We recommend adding the name=${currentLocale} to your site i18n config, but we will still try to run your site.
+Declared site config locales are: ${i18nConfig.locales}`;
+    return i18nConfig.locales.concat(currentLocale) as [string, ...string[]];
+  }
+  return i18nConfig.locales;
+}
+
 export async function loadI18n({
   siteDir,
   config,
@@ -114,14 +140,10 @@ export async function loadI18n({
 }): Promise<I18n> {
   const {i18n: i18nConfig} = config;
 
-  if (!i18nConfig.locales.includes(currentLocale)) {
-    logger.warn`The locale name=${currentLocale} was not found in your site configuration: Available locales are: ${i18nConfig.locales}
-Note: Docusaurus only support running one locale at a time.`;
-  }
-
-  const locales = i18nConfig.locales.includes(currentLocale)
-    ? i18nConfig.locales
-    : (i18nConfig.locales.concat(currentLocale) as [string, ...string[]]);
+  const locales = loadI18nLocaleList({
+    i18nConfig,
+    currentLocale,
+  });
 
   async function getFullLocaleConfig(
     locale: string,
@@ -131,7 +153,7 @@ Note: Docusaurus only support running one locale at a time.`;
       I18nLocaleConfig,
       'translate' | 'url' | 'baseUrl'
     > = {
-      ...getDefaultLocaleConfig(locale),
+      ...getDefaultLocaleConfig(localeConfigInput.htmlLang ?? locale),
       ...localeConfigInput,
     };