perf(build): reuse lastUpdated from markdown rendering in sitemap generation

Previously generateSitemap re-read and re-parsed every source file to
compute lastmod, reconstructing source paths from URLs. The transform
hook now records the already-computed pageData.lastUpdated per page,
keyed by its rewrite-applied relativePath. Dynamic route pages now get
a lastmod too (from their route template), which the old file lookup
could not resolve.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/node/build/build.ts

@@ -12,6 +12,7 @@ import { slash, type Awaitable, type HeadConfig } from '../shared'
 import { deserializeFunctions, serializeFunctions } from '../utils/fnSerialize'
 import { nativeImport } from '../utils/nativeImport'
 import { task } from '../utils/task'
+import type { PageMeta } from '../plugin'
 import { bundle } from './bundle'
 import { generateSitemap } from './generateSitemap'
 import { renderPage } from './render'
@@ -51,10 +52,13 @@ export async function build(
     delete buildOptions.outDir
   }
 
+  const pageMetaMap = Object.create(null) as Record<string, PageMeta>
+
   try {
     const { clientResult, serverResult, pageToHashMap } = await bundle(
       siteConfig,
-      buildOptions
+      buildOptions,
+      pageMetaMap
     )
 
     if (process.env.BUNDLE_ONLY) {
@@ -172,7 +176,7 @@ export async function build(
     }
   }
 
-  await generateSitemap(siteConfig)
+  await generateSitemap(siteConfig, pageMetaMap)
   await siteConfig.buildEnd?.(siteConfig)
   clearCache()
 

src/node/build/bundle.ts

@@ -12,7 +12,7 @@ import {
 } from 'vite'
 import { APP_PATH } from '../alias'
 import type { SiteConfig } from '../config'
-import { createVitePressPlugin } from '../plugin'
+import { createVitePressPlugin, type PageMeta } from '../plugin'
 import { escapeRegExp, sanitizeFileName, slash } from '../shared'
 import { task } from '../utils/task'
 import { buildMPAClient } from './buildMPAClient'
@@ -38,7 +38,8 @@ const excludedModules = [
 // bundles the VitePress app for both client AND server.
 export async function bundle(
   config: SiteConfig,
-  options: BuildOptions
+  options: BuildOptions,
+  pageMetaMap?: Record<string, PageMeta>
 ): Promise<{
   clientResult: Rolldown.RolldownOutput | null
   serverResult: Rolldown.RolldownOutput
@@ -83,7 +84,8 @@ export async function bundle(
       config,
       ssr,
       pageToHashMap,
-      clientJSMap
+      clientJSMap,
+      pageMetaMap
     ),
     ssr: { noExternal: ['vitepress', '@docsearch/css'] },
     build: {

src/node/build/generateSitemap.ts

@@ -1,4 +1,3 @@
-import matter from 'gray-matter'
 import fs from 'node:fs'
 import path from 'node:path'
 import {
@@ -9,78 +8,72 @@ import {
   type NewsItem
 } from 'sitemap'
 import type { SiteConfig } from '../config'
-import { slash } from '../shared'
-import { getGitTimestamp } from '../utils/getGitTimestamp'
+import type { PageMeta } from '../plugin'
 import { task } from '../utils/task'
 
-export async function generateSitemap(siteConfig: SiteConfig) {
+export async function generateSitemap(
+  siteConfig: SiteConfig,
+  pageMetaMap: Record<string, PageMeta>
+) {
   if (!siteConfig.sitemap?.hostname) return
 
-  const getLastmod = async (url: string) => {
-    if (!siteConfig.lastUpdated) return undefined
-
-    let file = url.replace(/(^|\/)$/, '$1index')
-    file = file.replace(/(\.html)?$/, '.md')
-    file = siteConfig.rewrites.inv[file] || file
-    file = path.join(siteConfig.srcDir, file)
-
-    if (!fs.existsSync(file)) return undefined
-
-    const { data } = matter.read(file)
-    if (data.lastUpdated === false) return undefined
-    if (data.lastUpdated instanceof Date) return +data.lastUpdated
-
-    return (await getGitTimestamp(slash(file))) || undefined
-  }
-
   await task('generating sitemap', async () => {
     const locales = siteConfig.userConfig.locales || {}
-    const filteredLocales = Object.keys(locales).filter(
-      (locale) => locales[locale].lang && locale !== 'root'
-    )
     const defaultLang =
-      locales?.root?.lang || siteConfig.userConfig.lang || 'en-US'
+      locales.root?.lang || siteConfig.userConfig.lang || 'en-US'
 
-    const pages = siteConfig.pages.map(
-      (page) => siteConfig.rewrites.map[page] || page
+    // locale directories whose pages are translations of each other
+    const localeDirs = Object.keys(locales).filter(
+      (locale) => locale !== 'root' && locales[locale].lang
     )
 
-    const groupedPages: Record<string, { lang: string; url: string }[]> = {}
-    pages.forEach((page) => {
-      const locale = page.split('/')[0]
-      const lang = locales[locale]?.lang || defaultLang
+    // group each page with its translations under a locale-independent key
+    const pageGroups: Record<
+      string,
+      { lang: string; url: string; lastmod?: number }[]
+    > = {}
 
-      let url = page.replace(/(^|\/)index\.md$/, '$1')
-      url = url.replace(/\.md$/, siteConfig.cleanUrls ? '' : '.html')
-      if (filteredLocales.includes(locale)) page = page.slice(locale.length + 1)
+    for (const sourcePage of siteConfig.pages) {
+      const page = siteConfig.rewrites.map[sourcePage] || sourcePage
+      const localeDir = page.split('/')[0]
 
-      if (!groupedPages[page]) groupedPages[page] = []
-      groupedPages[page].push({ url, lang })
-    })
+      const url = page
+        .replace(/(^|\/)index\.md$/, '$1')
+        .replace(/\.md$/, siteConfig.cleanUrls ? '' : '.html')
 
-    const _items = await Promise.all(
-      Object.values(groupedPages).map(async (pages) => {
-        if (pages.length < 2)
-          return { url: pages[0].url, lastmod: await getLastmod(pages[0].url) }
+      const key = localeDirs.includes(localeDir)
+        ? page.slice(localeDir.length + 1)
+        : page
 
-        return await Promise.all(
-          pages.map(async ({ url }) => {
-            return { url, lastmod: await getLastmod(url), links: pages }
-          })
-        )
+      ;(pageGroups[key] ??= []).push({
+        lang: locales[localeDir]?.lang || defaultLang,
+        url,
+        lastmod: pageMetaMap[page]?.lastUpdated || undefined
       })
+    }
+
+    // translated pages link to all their variants (including themselves)
+    let items: SitemapItem[] = Object.values(pageGroups).flatMap((variants) =>
+      variants.length < 2
+        ? { url: variants[0].url, lastmod: variants[0].lastmod }
+        : variants.map(({ url, lastmod }) => ({
+            url,
+            lastmod,
+            links: variants
+          }))
     )
-
-    let items: SitemapItem[] = _items.flat()
     items = (await siteConfig.sitemap?.transformItems?.(items)) || items
 
-    const sitemapStream = new SitemapStream(siteConfig.sitemap)
     const sitemapPath = path.join(siteConfig.outDir, 'sitemap.xml')
+    const sitemapStream = new SitemapStream(siteConfig.sitemap)
     const writeStream = fs.createWriteStream(sitemapPath)
 
     sitemapStream.pipe(writeStream)
     items.forEach((item) => sitemapStream.write(item))
     sitemapStream.end()
+    await new Promise((resolve, reject) =>
+      writeStream.on('finish', resolve).on('error', reject)
+    )
   })
 }
 

src/node/plugin.ts

@@ -65,11 +65,17 @@ const isPageChunk = <T extends Rolldown.OutputChunk | Rolldown.RenderedChunk>(
 
 const cleanUrl = (url: string): string => url.replace(/[?#].*$/s, '')
 
+// per-page metadata collected during transform, keyed by relativePath
+export interface PageMeta {
+  lastUpdated?: number
+}
+
 export async function createVitePressPlugin(
   siteConfig: SiteConfig,
   ssr = false,
   pageToHashMap?: Record<string, string>,
   clientJSMap?: Record<string, string>,
+  pageMetaMap?: Record<string, PageMeta>,
   restartServer?: () => Promise<void>
 ) {
   const {
@@ -218,6 +224,11 @@ export async function createVitePressPlugin(
             code,
             id
           )
+          if (pageMetaMap) {
+            pageMetaMap[pageData.relativePath] = {
+              lastUpdated: pageData.lastUpdated
+            }
+          }
           allDeadLinks.push(...deadLinks)
           if (includes.length) {
             includes.forEach((i) => {

src/node/server.ts

@@ -17,7 +17,14 @@ export async function createServer(
     root: config.srcDir,
     base: config.site.base,
     cacheDir: config.cacheDir,
-    plugins: await createVitePressPlugin(config, false, {}, {}, restartServer),
+    plugins: await createVitePressPlugin(
+      config,
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      restartServer
+    ),
     server,
     customLogger: config.logger,
     configFile: config.vite?.configFile