fix: retry file reads when out of file descriptors

Content, include, route-template and search reads now run
concurrently, so large sites can hit EMFILE/ENFILE. Route all async
reads through a shared readFile util that retries with backoff.

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

src/node/contentLoader.ts

@@ -1,5 +1,5 @@
 import matter from 'gray-matter'
-import { readFile, stat } from 'node:fs/promises'
+import { stat } from 'node:fs/promises'
 import path from 'node:path'
 import pMap from 'p-map'
 import { normalizePath } from 'vite'
@@ -9,6 +9,7 @@ import {
   mergeMarkdownLocales
 } from './markdown/markdown'
 import type { Awaitable, MarkdownEnv } from './shared'
+import { readFile } from './utils/fs'
 import { glob, normalizeGlob, type GlobOptions } from './utils/glob'
 
 export interface ContentOptions<T = ContentData[]> {
@@ -121,7 +122,7 @@ export function createContentLoader<T = ContentData[]>(
 
           if (cached && timestamp === cached.timestamp) return cached.data
 
-          const src = await readFile(file, 'utf8')
+          const src = await readFile(file)
 
           const renderExcerpt = options.excerpt
           const { data: frontmatter, excerpt } = matter(

src/node/plugins/dynamicRoutesPlugin.ts

@@ -1,5 +1,4 @@
 import fs from 'node:fs'
-import { readFile } from 'node:fs/promises'
 import path from 'node:path'
 import c from 'picocolors'
 import pm from 'picomatch'
@@ -13,6 +12,7 @@ import {
 } from 'vite'
 import type { Awaitable } from '../shared'
 import { type SiteConfig, type UserConfig } from '../siteConfig'
+import { readFile } from '../utils/fs'
 import { glob, normalizeGlob, type GlobOptions } from '../utils/glob'
 import { ModuleGraph } from '../utils/moduleGraph'
 import { resolveRewrites } from './rewritesPlugin'
@@ -158,7 +158,7 @@ export const dynamicRoutesPlugin = async (
           moduleGraph.add(id, [routeFile])
           moduleGraph.add(routeFile, [matched.loaderPath])
 
-          let baseContent = await readFile(routeFile, 'utf8')
+          let baseContent = await readFile(routeFile)
 
           // inject raw content
           // this is intended for integration with CMS

src/node/plugins/localSearchPlugin.ts

@@ -1,6 +1,5 @@
 import { prefixRegex } from '@rolldown/pluginutils'
 import MiniSearch from 'minisearch'
-import { readFile } from 'node:fs/promises'
 import path from 'node:path'
 import { createDebug } from 'obug'
 import type { Plugin, ViteDevServer } from 'vite'
@@ -8,6 +7,7 @@ import type { SiteConfig } from '../config'
 import type { DefaultTheme } from '../defaultTheme'
 import { createMarkdownRenderer } from '../markdown/markdown'
 import { getLocaleForPath, slash, type MarkdownEnv } from '../shared'
+import { readFile } from '../utils/fs'
 import { processIncludes } from '../utils/processIncludes'
 
 const debug = createDebug('vitepress:local-search')
@@ -52,7 +52,7 @@ export async function localSearchPlugin(
     const { srcDir, cleanUrls = false } = siteConfig
     const relativePath = slash(path.relative(srcDir, file))
     const env: MarkdownEnv = { path: file, relativePath, cleanUrls }
-    const raw = await readFile(file, 'utf8').catch((e) => {
+    const raw = await readFile(file).catch((e) => {
       if (e.code === 'ENOENT') {
         debug(`File not found: ${file}`)
         return ''

src/node/serve/serve.ts

@@ -1,9 +1,9 @@
 import compression from '@polka/compression'
-import { readFile } from 'node:fs/promises'
 import path from 'node:path'
 import polka, { type IOptions } from 'polka'
 import sirv from 'sirv'
 import { resolveConfig } from '../config'
+import { readFile } from '../utils/fs'
 
 export interface ServeOptions {
   base?: string
@@ -21,10 +21,7 @@ export async function serve(options: ServeOptions = {}) {
 
   const notAnAsset = (pathname: string) =>
     !pathname.includes(`/${config.assetsDir}/`)
-  const notFound = await readFile(
+  const notFound = await readFile(path.resolve(config.outDir, './404.html'))
-    path.resolve(config.outDir, './404.html'),
-    'utf8'
-  )
   const onNoMatch: IOptions['onNoMatch'] = (req, res) => {
     res.statusCode = 404
     if (notAnAsset(req.path)) res.write(notFound)

src/node/utils/fs.ts

@@ -0,0 +1,19 @@
+import { readFile as fsReadFile } from 'node:fs/promises'
+
+const retryCodes = new Set(['EMFILE', 'ENFILE'])
+
+/**
+ * Reads a file as utf8, retrying with backoff when the process is
+ * temporarily out of file descriptors (EMFILE/ENFILE).
+ */
+export async function readFile(file: string): Promise<string> {
+  for (let attempt = 0; ; attempt++) {
+    try {
+      return await fsReadFile(file, 'utf8')
+    } catch (e) {
+      const code = (e as NodeJS.ErrnoException).code
+      if (attempt >= 9 || !code || !retryCodes.has(code)) throw e
+      await new Promise((resolve) => setTimeout(resolve, 2 ** attempt * 10))
+    }
+  }
+}

src/node/utils/processIncludes.ts

@@ -1,9 +1,9 @@
 import matter from 'gray-matter'
 import { replaceAsync, type MarkdownItAsync } from 'markdown-it-async'
-import { readFile } from 'node:fs/promises'
 import path from 'node:path'
 import { findRegion } from '../markdown/plugins/snippet'
 import { slash, type MarkdownEnv } from '../shared'
+import { readFile } from './fs'
 
 export function processIncludes(
   md: MarkdownItAsync,
@@ -41,7 +41,7 @@ export function processIncludes(
     // chain are cycles, the same file may still be included by siblings
     if (includePath === file || ancestors.includes(includePath)) return m
 
-    let content = await readFile(includePath, 'utf8')
+    let content = await readFile(includePath)
 
     if (region) {
       const [regionName] = region