perf: pre transform requests while opening the browser (#12809)

packages/vite/src/node/server/index.ts

@@ -1,5 +1,6 @@
 import path from 'node:path'
 import type * as net from 'node:net'
+import { get as httpGet } from 'node:http'
 import type * as http from 'node:http'
 import { performance } from 'node:perf_hooks'
 import connect from 'connect'
@@ -447,6 +448,31 @@ export async function _createServer(
             ? new URL(options.open, url).href
             : url
 
+        // We know the url that the browser would be opened to, so we can
+        // start the request while we are awaiting the browser. This will
+        // start the crawling of static imports ~500ms before.
+        setTimeout(() => {
+          httpGet(
+            path,
+            {
+              headers: {
+                // Allow the history middleware to redirect to /index.html
+                Accept: 'text/html',
+              },
+            },
+            (res) => {
+              res.on('end', () => {
+                // Ignore response, scripts discovered while processing the entry
+                // will be preprocessed (server.config.server.preTransformRequests)
+              })
+            },
+          )
+            .on('error', () => {
+              // Ignore errors
+            })
+            .end()
+        }, 0)
+
         _openBrowser(path, true, server.config.logger)
       } else {
         server.config.logger.warn('No URL available to open in browser')