Next.jsにおけるSEOとi18n：翻訳だけでは不十分

import type { Metadata } from "next";import { locales, defaultLocale } from "@/i18n";import { getTranslations, unstable_setRequestLocale } from "next-intl/server";function localizedPath(locale: string, path: string) {return locale === defaultLocale ? path : `/${locale}${path}`;}export async function generateMetadata({params,}: {params: { locale: string };}): Promise<Metadata> {const { locale } = params;const t = await getTranslations({ locale, namespace: "about" });const url = "/about";const languages = Object.fromEntries(  locales.map((l) => [l, localizedPath(l, url)]));return {  title: t("title"),  description: t("description"),  alternates: {    canonical: localizedPath(locale, url),    languages: { ...languages, "x-default": url },  },};}// ... ページの残りのコード

import type { MetadataRoute } from "next";import { locales, defaultLocale } from "@/i18n";const origin = "https://example.com";const formatterLocalizedPath = (locale: string, path: string) =>locale === defaultLocale ? `${origin}${path}` : `${origin}/${locale}${path}`;export default function sitemap(): MetadataRoute.Sitemap {const aboutLanguages = Object.fromEntries(  locales.map((l) => [l, formatterLocalizedPath(l, "/about")]));return [  {    url: formatterLocalizedPath(defaultLocale, "/about"),    lastModified: new Date(),    changeFrequency: "monthly", // 毎月の更新頻度    priority: 0.7, // 優先度    alternates: { languages: aboutLanguages }, // 言語別の代替URL  },];}

import type { MetadataRoute } from "next";import { locales, defaultLocale } from "@/i18n";const origin = "https://example.com";const withAllLocales = (path: string) => [path,...locales.filter((l) => l !== defaultLocale).map((l) => `/${l}${path}`), // デフォルトロケール以外のパスを追加];export default function robots(): MetadataRoute.Robots {const disallow = [  ...withAllLocales("/dashboard"), // /dashboard へのアクセス禁止  ...withAllLocales("/admin"), // /admin へのアクセス禁止];return {  rules: { userAgent: "*", allow: ["/"], disallow },  host: origin,  sitemap: `${origin}/sitemap.xml`,};}

export const locales = ["en", "fr"] as const;export type Locale = (typeof locales)[number];export const defaultLocale: Locale = "en";/** デフォルトロケールでない場合はロケールをパスの前に付ける */export function localizedPath(locale: string, path: string) {return locale === defaultLocale ? path : `/${locale}${path}`;}/** 絶対URLヘルパー */const ORIGIN = "https://example.com";export function abs(locale: string, path: string) {return `${ORIGIN}${localizedPath(locale, path)}`;}

import type { Metadata } from "next";import { locales, defaultLocale, localizedPath } from "@/i18n.config";export async function generateMetadata({params,}: {params: { locale: string };}): Promise<Metadata> {const { locale } = params;// 正しいJSONファイルを動的にインポートするconst messages = (await import(`@/../public/locales/${locale}/about.json`))  .default;const languages = Object.fromEntries(  locales.map((l) => [l, localizedPath(l, "/about")]));return {  title: messages.title,  description: messages.description,  alternates: {    canonical: localizedPath(locale, "/about"),    languages: { ...languages, "x-default": "/about" },  },};}export default async function AboutPage() {return <h1>About</h1>;}

import type { MetadataRoute } from "next";import { locales, defaultLocale, abs } from "@/i18n.config";export default function sitemap(): MetadataRoute.Sitemap {const languages = Object.fromEntries(  locales.map((l) => [l, abs(l, "/about")]));return [  {    url: abs(defaultLocale, "/about"),    lastModified: new Date(),    changeFrequency: "monthly",    priority: 0.7,    alternates: { languages },  },];}

import type { MetadataRoute } from "next";import { locales, defaultLocale, localizedPath } from "@/i18n.config";const ORIGIN = "https://example.com";const expandAllLocales = (path: string) => [localizedPath(defaultLocale, path),...locales  .filter((l) => l !== defaultLocale)  .map((l) => localizedPath(l, path)),];export default function robots(): MetadataRoute.Robots {const disallow = [  ...expandAllLocales("/dashboard"),  ...expandAllLocales("/admin"),];return {  rules: { userAgent: "*", allow: ["/"], disallow },  host: ORIGIN,  sitemap: `${ORIGIN}/sitemap.xml`,};}

import { getIntlayer, getMultilingualUrls } from "intlayer";import type { Metadata } from "next";import type { LocalPromiseParams } from "next-intlayer";export const generateMetadata = async ({params,}: LocalPromiseParams): Promise<Metadata> => {const { locale } = await params;const metadata = getIntlayer("page-metadata", locale);/** * 各ロケールのすべてのURLを含むオブジェクトを生成します。 * * 例: * ```ts *  getMultilingualUrls('/about'); * *  // 戻り値 *  // { *  //   en: '/about', *  //   fr: '/fr/about', *  //   es: '/es/about', *  // } * ``` */const multilingualUrls = getMultilingualUrls("/about");return {  ...metadata,  alternates: {    canonical: multilingualUrls[locale as keyof typeof multilingualUrls],    languages: { ...multilingualUrls, "x-default": "/about" },  },};};// ... ページの残りのコード

import { getMultilingualUrls } from "intlayer";import type { MetadataRoute } from "next";const sitemap = (): MetadataRoute.Sitemap => [{  url: "https://example.com/about",  alternates: {    languages: { ...getMultilingualUrls("https://example.com/about") },  },},];

import { getMultilingualUrls } from "intlayer";import type { MetadataRoute } from "next";// すべての多言語URLを取得する関数const getAllMultilingualUrls = (urls: string[]) =>urls.flatMap((url) => Object.values(getMultilingualUrls(url)) as string[]);// robots.txtの設定を生成const robots = (): MetadataRoute.Robots => ({rules: {  userAgent: "*", // すべてのユーザーエージェントに適用  allow: ["/"], // ルートパスは許可  disallow: getAllMultilingualUrls(["/dashboard"]), // /dashboard以下の多言語URLはクロール禁止},host: "https://example.com", // ホスト名sitemap: `https://example.com/sitemap.xml`, // サイトマップのURL});export default robots;