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`,  };}

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 { 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;