fix: make vite dev server open on a free port (#15756)

npm/vite-dev-server/cypress.json

@@ -1,5 +1,6 @@
 {
   "pluginsFile": "cypress/plugins.js",
+  "video": false,
   "testFiles": "**/*.spec.*",
   "componentFolder": "cypress/components",
   "supportFile": "cypress/support/support.js"

npm/vite-dev-server/package.json

@@ -12,7 +12,8 @@
     "watch": "tsc -w"
   },
   "dependencies": {
-    "debug": "4.3.2"
+    "debug": "^4.3.2",
+    "get-port": "^5.1.1"
   },
   "devDependencies": {
     "@cypress/react": "0.0.0-development",
@@ -27,7 +28,7 @@
     "vue": "3.0.9"
   },
   "peerDependencies": {
-    "vite": ">= 2"
+    "vite": ">= 2.1.3"
   },
   "files": [
     "dist",

npm/vite-dev-server/src/index.ts

@@ -1,23 +1,9 @@
-import { EventEmitter } from 'events'
 import { debug as debugFn } from 'debug'
-import { start as createDevServer } from './startServer'
-import { UserConfig } from 'vite'
 import { Server } from 'http'
+import { start as createDevServer, StartDevServer } from './startServer'
 const debug = debugFn('cypress:vite-dev-server:vite')
 
-interface Options {
-  specs: any[] // Cypress.Cypress['spec'][] // Why isn't this working? It works for webpack-dev-server
-  config: Record<string, string>
-  devServerEvents: EventEmitter
-  [key: string]: unknown
-}
-
-export interface StartDevServer {
-  /* this is the Cypress options object */
-  options: Options
-  /* support passing a path to the user's webpack config */
-  viteConfig?: UserConfig // TODO: implement taking in the user's vite configuration. Right now we don't
-}
+export { StartDevServer }
 
 export interface ResolvedDevServerConfig {
   port: number

npm/vite-dev-server/src/makeCypressPlugin.ts

@@ -1,4 +1,3 @@
-import { EventEmitter } from 'events'
 import { resolve } from 'path'
 import { readFile } from 'fs'
 import { promisify } from 'util'
@@ -24,7 +23,7 @@ export const makeCypressPlugin = (
       if (env) {
         return {
           define: {
-            'import.meta.env.__cypress_supportPath': JSON.stringify(resolve(projectRoot, supportFilePath)),
+            'import.meta.env.__cypress_supportPath': JSON.stringify(supportFilePath ? resolve(projectRoot, supportFilePath) : undefined),
             'import.meta.env.__cypress_originAutUrl': JSON.stringify('__cypress/iframes/'),
           },
         }

npm/vite-dev-server/src/startServer.ts

@@ -1,47 +1,49 @@
 import Debug from 'debug'
-import { StartDevServer } from '.'
-import { createServer, ViteDevServer, InlineConfig } from 'vite'
+import { createServer, ViteDevServer, InlineConfig, UserConfig } from 'vite'
 import { dirname, resolve } from 'path'
+import getPort from 'get-port'
 import { makeCypressPlugin } from './makeCypressPlugin'
-import { EventEmitter } from 'events'
 
 const debug = Debug('cypress:vite-dev-server:start')
 
-// TODO: Pull in types for Options so we can infer these
-const serverConfig = (projectRoot: string, supportFilePath: string, devServerEvents: EventEmitter): InlineConfig => {
-  return {
-    root: resolve(__dirname, projectRoot),
-    base: '/__cypress/src/',
-    plugins: [makeCypressPlugin(projectRoot, supportFilePath, devServerEvents)],
-    server: {
-      port: 0,
-    },
-    resolve: {
-      alias: {
-        // Necessary to avoid a "prefixIdentifiers" issue from slots mounting
-        // Could be resolved in test-utils
-        '@vue/compiler-core': resolve(dirname(require.resolve('@vue/compiler-core')), 'dist', 'compiler-core.cjs.js'),
-      },
-    },
-  }
+interface Options {
+  specs: Cypress.Cypress['spec'][]
+  config: Record<string, string>
+  devServerEvents: EventEmitter
+  [key: string]: unknown
+}
+
+export interface StartDevServer {
+  /* this is the Cypress options object */
+  options: Options
+  /* support passing a path to the user's webpack config */
+  viteConfig?: UserConfig // TODO: implement taking in the user's vite configuration. Right now we don't
 }
 
-const resolveServerConfig = ({ viteConfig, options }: StartDevServer) => {
-  const defaultServerConfig = serverConfig(
-    options.config.projectRoot,
-    options.config.supportFile,
-    options.devServerEvents,
-  )
+const resolveServerConfig = async ({ viteConfig, options }: StartDevServer): Promise<InlineConfig> => {
+  const { projectRoot, supportFile } = options.config
 
-  const requiredOptions = {
-    base: defaultServerConfig.base,
-    root: defaultServerConfig.root,
+  const requiredOptions: InlineConfig = {
+    base: '/__cypress/src/',
+    root: projectRoot,
   }
 
-  const finalConfig = { ...defaultServerConfig, ...viteConfig, ...requiredOptions }
+  const finalConfig: InlineConfig = { ...viteConfig, ...requiredOptions }
+
+  finalConfig.plugins = [...(viteConfig.plugins || []), makeCypressPlugin(projectRoot, supportFile, options.devServerEvents)]
+
+  // This alias is necessary to avoid a "prefixIdentifiers" issue from slots mounting
+  // only cjs compiler-core accepts using prefixIdentifiers in slots which vue test utils use.
+  // Could we resolve this usage in test-utils?
+  finalConfig.resolve = finalConfig.resolve || {}
+  finalConfig.resolve.alias = {
+    ...finalConfig.resolve.alias,
+    '@vue/compiler-core': resolve(dirname(require.resolve('@vue/compiler-core')), 'dist', 'compiler-core.cjs.js'),
+  },
+
+  finalConfig.server = finalConfig.server || {}
 
-  finalConfig.plugins = [...(viteConfig.plugins || []), defaultServerConfig.plugins[0]]
-  finalConfig.server.port = defaultServerConfig.server.port
+  finalConfig.server.port = await getPort({ port: 3000, host: 'localhost' }),
 
   debug(`the resolved server config is ${JSON.stringify(finalConfig, null, 2)}`)
 
@@ -55,7 +57,7 @@ export async function start (devServerOptions: StartDevServer): Promise<ViteDevS
   }
 
   debug('starting vite dev server')
-  const resolvedConfig = resolveServerConfig(devServerOptions)
+  const resolvedConfig = await resolveServerConfig(devServerOptions)
 
   return createServer(resolvedConfig)
 }