Remove Vite plugin delay in dev mode

We were using setTimeout to wait for the initial scan to complete before generating Tailwind CSS. Now that full builds wait until the bundle stage, dev builds can simply run immediately. This might generate Tailwind CSS twice, generating a FOUC, but will be faster than waiting for the timeout.

A [proposed Vite change](vitejs/vite#16135) could address the FOUC and extra build.

packages/@tailwindcss-vite/src/index.ts

@@ -115,35 +115,6 @@ export default function tailwindcss(): Plugin[] {
     return css
   }
 
-  // In dev mode, there isn't a hook to signal that we've seen all files. We use
-  // a timer, resetting it on each file seen, and trigger CSS generation when we
-  // haven't seen any new files after a timeout. If this triggers too early,
-  // there will be a FOOC and but CSS will regenerate after we've seen more files.
-  let initialScan = (() => {
-    // If too short, we're more likely to trigger a FOOC and generate CSS
-    // multiple times. If too long, we delay dev builds.
-    let delayInMs = 50
-
-    let timer: ReturnType<typeof setTimeout>
-    let resolve: () => void
-    let resolved = false
-
-    return {
-      tick() {
-        if (resolved) return
-        timer && clearTimeout(timer)
-        timer = setTimeout(resolve, delayInMs)
-      },
-
-      complete: new Promise<void>((_resolve) => {
-        resolve = () => {
-          resolved = true
-          _resolve()
-        }
-      }),
-    }
-  })()
-
   return [
     {
       // Step 1: Scan source files for candidates
@@ -161,7 +132,6 @@ export default function tailwindcss(): Plugin[] {
 
       // Scan index.html for candidates
       transformIndexHtml(html) {
-        initialScan.tick()
         let updated = scan(html, 'html')
 
         // In dev mode, if the generated CSS contains a URL that causes the
@@ -175,7 +145,6 @@ export default function tailwindcss(): Plugin[] {
 
       // Scan all other files for candidates
       transform(src, id) {
-        initialScan.tick()
         if (id.includes('/.vite/')) return
         let [filename] = id.split('?', 2)
         let extension = path.extname(filename).slice(1)
@@ -198,9 +167,6 @@ export default function tailwindcss(): Plugin[] {
 
         cssModules.add(id)
 
-        // For the initial load we must wait for all source files to be scanned
-        await initialScan.complete
-
         let css = generateCss(src)
         css = await transformWithPlugins(this, css)
         return { code: css }