feat: rewrite app.writeTemp to resolve IO race conditions (#862)

theme/src/node/enhance.ts

@@ -0,0 +1,53 @@
+/**
+ * 此增强为临时性措施，vuepress/core 将会在下个版本中实现
+ * 在 vuepress/core 下个版本是，应该删除此增强
+ */
+
+import type { App } from 'vuepress'
+import { fs, hash } from '@vuepress/utils'
+
+interface WriteTempCache {
+  hash?: string // content hash
+  current?: Promise<void> // the current writing promise
+  next?: () => Promise<void> // the next writing promise
+}
+
+export function enhanceApp(app: App): void {
+  // rewrite writeTemp to cache the writing promise
+  const cache = new Map<string, WriteTempCache>()
+  app.writeTemp = async function (file: string, content: string): Promise<string> {
+    const filePath = app.dir.temp(file)
+    const contentHash = hash(content)
+
+    let item = cache.get(filePath)
+    if (!item) {
+      cache.set(filePath, (item = {}))
+    }
+
+    // if content hash is the same as the last one, skip writing
+    if (item.hash === contentHash) {
+      return filePath
+    }
+
+    item.hash = contentHash
+
+    if (!item.current) {
+      item.current = (async () => {
+        await fs.outputFile(filePath, content)
+        // if there is a next writing promise, chain it with the current one
+        item.current = item.next?.()
+        return item.current
+      })()
+    }
+    else {
+      // if there is a current writing promise, save the next writing promise
+      item.next = async () => {
+        await fs.outputFile(filePath, content)
+        item.next = undefined
+        item.current = undefined
+      }
+    }
+    await item.current
+    return filePath
+  }
+}

theme/src/node/theme.ts

@@ -12,6 +12,7 @@ import {
   templateBuildRenderer,
 } from './config/index.js'
 import { detectThemeOptions, detectVersions } from './detector/index.js'
+import { enhanceApp } from './enhance.js'
 import { configLoader } from './loadConfig/index.js'
 import { createPages, extendsPageData } from './pages/index.js'
 import { setupPlugins } from './plugins/index.js'
@@ -39,6 +40,8 @@ import { perf, resolve, setTranslateLang, templates, THEME_NAME } from './utils/
  */
 export function plumeTheme(options: ThemeOptions = {}): Theme {
   return (app) => {
+    enhanceApp(app)
+
     setTranslateLang(app.options.lang)
     perf.init(app.env.isDebug)