Fix Vite issues with SolidStart (#16052)

Fixes #16045

This PR fixes two Vite issues found with SolidStart:

- SolidStart seems to emit an empty HTML chunk (where the content is
literally just `/`) with _no pathname_. Since we use the path to
generate an `id` for HTML chunks, this would currently cause a crash.
This was reported in #16045
- While testing the fix for the above, we also found that hot reloading
was not working in SolidStart since `4.0.0-alpha.22`. After doing some
bisecting we found that this is happening as SolidStart has the same
module ID in different servers and we were invalidating the root when we
shouldn't. After trying to restructure this code so that it only cleans
up the root when it is _no longer part of any server_, we noticed some
other compatibility issues with Nuxt and SvelteKit. It seems that the
safest bet is to no longer update a root at all during rebuilds in the
SSR step. This makes `invalidateAllRoots` a function that only notifiers
the servers about a change which is conceptually also less confusing.

## Test plan

- Added an integration test for SolidStart dev mode
- Manually tested the dev mode across all Vite based templates in
https://github.com/philipp-spiess/tailwindcss-playgrounds: Astro, Nuxt,
Remix, Solid, SvelteKit, and Vue.

---------

Co-authored-by: Robin Malfait <malfait.robin@gmail.com>

CHANGELOG.md

@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Only generate positive `grid-cols-*` and `grid-rows-*` utilities ([#16020](https://github.com/tailwindlabs/tailwindcss/pull/16020))
 - Ensure we process Tailwind CSS features when only using `@reference` or `@variant` ([#16057](https://github.com/tailwindlabs/tailwindcss/pull/16057))
 - Refactor gradient implementation to work around [prettier/prettier#17058](https://github.com/prettier/prettier/issues/17058) ([#16072](https://github.com/tailwindlabs/tailwindcss/pull/16072))
+- Vite: Ensure hot-reloading works with SolidStart setups ([#16052](https://github.com/tailwindlabs/tailwindcss/pull/16052))
+- Vite: Fix a crash when starting the development server in SolidStart setups ([#16052](https://github.com/tailwindlabs/tailwindcss/pull/16052))
 
 ## [4.0.1] - 2025-01-29
 

integrations/vite/solidstart.test.ts

@@ -0,0 +1,108 @@
+import { candidate, css, fetchStyles, js, json, retryAssertion, test, ts } from '../utils'
+
+const WORKSPACE = {
+  'package.json': json`
+    {
+      "type": "module",
+      "dependencies": {
+        "@solidjs/start": "^1",
+        "solid-js": "^1",
+        "vinxi": "^0",
+        "@tailwindcss/vite": "workspace:^",
+        "tailwindcss": "workspace:^"
+      }
+    }
+  `,
+  'jsconfig.json': json`
+    {
+      "compilerOptions": {
+        "jsx": "preserve",
+        "jsxImportSource": "solid-js"
+      }
+    }
+  `,
+  'app.config.js': ts`
+    import { defineConfig } from '@solidjs/start/config'
+    import tailwindcss from '@tailwindcss/vite'
+
+    export default defineConfig({
+      vite: {
+        plugins: [tailwindcss()],
+      },
+    })
+  `,
+  'src/entry-server.jsx': js`
+    // @refresh reload
+    import { createHandler, StartServer } from '@solidjs/start/server'
+
+    export default createHandler(() => (
+      <StartServer
+        document={({ assets, children, scripts }) => (
+          <html lang="en">
+            <head>{assets}</head>
+            <body>
+              <div id="app">{children}</div>
+              {scripts}
+            </body>
+          </html>
+        )}
+      />
+    ))
+  `,
+  'src/entry-client.jsx': js`
+    // @refresh reload
+    import { mount, StartClient } from '@solidjs/start/client'
+
+    mount(() => <StartClient />, document.getElementById('app'))
+  `,
+  'src/app.jsx': js`
+    import './app.css'
+    export default function App() {
+      return <h1 class="underline">Hello world!</h1>
+    }
+  `,
+  'src/app.css': css`@import 'tailwindcss';`,
+}
+
+test(
+  'dev mode',
+  {
+    fs: WORKSPACE,
+  },
+  async ({ fs, spawn, expect }) => {
+    let process = await spawn('pnpm vinxi dev', {
+      env: {
+        TEST: 'false', // VERY IMPORTANT OTHERWISE YOU WON'T GET OUTPUT
+        NODE_ENV: 'development',
+      },
+    })
+
+    let url = ''
+    await process.onStdout((m) => {
+      let match = /Local:\s*(http.*)\//.exec(m)
+      if (match) url = match[1]
+      return Boolean(url)
+    })
+
+    await retryAssertion(async () => {
+      let css = await fetchStyles(url)
+      expect(css).toContain(candidate`underline`)
+    })
+
+    await retryAssertion(async () => {
+      await fs.write(
+        'src/app.jsx',
+        js`
+          import './app.css'
+          export default function App() {
+            return <h1 class="underline font-bold">Hello world!</h1>
+          }
+        `,
+      )
+
+      let css = await fetchStyles(url)
+      expect(css).toContain(candidate`underline`)
+      expect(css).toContain(candidate`font-bold`)
+    })
+  },
+)

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

@@ -63,7 +63,7 @@ export default function tailwindcss(): Plugin[] {
     )
   })
 
-  function scanFile(id: string, content: string, extension: string, isSSR: boolean) {
+  function scanFile(id: string, content: string, extension: string) {
     for (let dependency of IGNORED_DEPENDENCIES) {
       // We validated that Vite IDs always use posix style path separators, even on Windows.
       // In dev build, Vite precompiles dependencies
@@ -83,26 +83,16 @@ export default function tailwindcss(): Plugin[] {
     }
 
     if (updated) {
-      invalidateAllRoots(isSSR)
+      invalidateAllRoots()
     }
   }
 
-  function invalidateAllRoots(isSSR: boolean) {
+  function invalidateAllRoots() {
     for (let server of servers) {
       let updates: Update[] = []
-      for (let [id, root] of roots.entries()) {
+      for (let [id] of roots.entries()) {
         let module = server.moduleGraph.getModuleById(id)
-        if (!module) {
-          // Note: Removing this during SSR is not safe and will produce
-          // inconsistent results based on the timing of the removal and
-          // the order / timing of transforms.
-          if (!isSSR) {
-            // It is safe to remove the item here since we're iterating on a copy
-            // of the keys.
-            roots.delete(id)
-          }
-          continue
-        }
+        if (!module) continue
 
         roots.get(id).requiresRebuild = false
         server.moduleGraph.invalidateModule(module)
@@ -113,7 +103,6 @@ export default function tailwindcss(): Plugin[] {
           timestamp: Date.now(),
         })
       }
-
       if (updates.length > 0) {
         server.hot.send({ type: 'update', updates })
       }
@@ -210,12 +199,15 @@ export default function tailwindcss(): Plugin[] {
 
       // Scan all non-CSS files for candidates
       transformIndexHtml(html, { path }) {
-        scanFile(path, html, 'html', isSSR)
+        // SolidStart emits HTML chunks with an undefined path and the html content of `\`.
+        if (!path) return
+
+        scanFile(path, html, 'html')
       },
       transform(src, id, options) {
         let extension = getExtension(id)
         if (isPotentialCssRootFile(id)) return
-        scanFile(id, src, extension, options?.ssr ?? false)
+        scanFile(id, src, extension)
       },
     },