feat(vite-dev-server): migrate to async fs operations for better perf…

npm/vite-dev-server/src/plugins/cypress.ts

@@ -2,7 +2,7 @@ import debugFn from 'debug'
 import type { ModuleNode, PluginOption, ViteDevServer } from 'vite-7'
 import type { Vite } from '../getVite.js'
 import { parse, HTMLElement } from 'node-html-parser'
-import fs from 'fs'
+import fs from 'fs/promises'
 
 import type { ViteDevServerConfig } from '../devServer.js'
 import path from 'path'
@@ -33,6 +33,7 @@ export const Cypress = (
   vite: Vite,
 ): PluginOption => {
   let base = '/'
+  let loaderPromise: Promise<string> | null = null
 
   const projectRoot = options.cypressConfig.projectRoot
   const supportFilePath = options.cypressConfig.supportFile ? path.resolve(projectRoot, options.cypressConfig.supportFile) : false
@@ -42,9 +43,31 @@ export const Cypress = (
   const indexHtmlFile = options.cypressConfig.indexHtmlFile
 
   let specsPathsSet = getSpecsPathsSet(specs)
-  // TODO: use async fs methods here
-  // eslint-disable-next-line no-restricted-syntax
-  let loader = fs.readFileSync(INIT_FILEPATH, 'utf8')
+
+  // Load the init file asynchronously with proper error handling
+  const loadInitFile = async (): Promise<string> => {
+    try {
+      const content = await fs.readFile(INIT_FILEPATH, 'utf8')
+
+      debug(`Successfully loaded init file from ${INIT_FILEPATH}`)
+
+      return content
+    } catch (error) {
+      debug(`Failed to load init file from ${INIT_FILEPATH}:`, error)
+      throw new Error(`Failed to load Cypress init file: ${error instanceof Error ? error.message : 'Unknown error'}`)
+    }
+  }
+
+  const getLoaderPromise = () => {
+    if (!loaderPromise) {
+      loaderPromise = loadInitFile().catch((err) => {
+        loaderPromise = null
+        throw err
+      })
+    }
+
+    return loaderPromise
+  }
 
   devServerEvents.on('dev-server:specs:changed', ({ specs, options }: { specs: Spec[], options?: { neededForJustInTimeCompile: boolean }}) => {
     if (options?.neededForJustInTimeCompile) {
@@ -79,7 +102,7 @@ export const Cypress = (
 
       debug('resolved the indexHtmlPath as', indexHtmlPath, 'from', indexHtmlFile)
 
-      let indexHtmlContent = await fs.promises.readFile(indexHtmlPath, { encoding: 'utf8' })
+      let indexHtmlContent = await fs.readFile(indexHtmlPath, { encoding: 'utf8' })
 
       // Inject the script tags
       indexHtmlContent = indexHtmlContent.replace(
@@ -92,6 +115,9 @@ export const Cypress = (
       // find </body> last index
       const endOfBody = indexHtmlContent.lastIndexOf('</body>')
 
+      // Get the loader content asynchronously
+      const loader = await getLoaderPromise()
+
       // insert the script in the end of the body
       const newHtml = `
         ${indexHtmlContent.substring(0, endOfBody)}