Fix detection when project contains stylesheets that import the "main" stylesheet (#1218)

Fixes #1217

This issue kinda reveals that the entire detection around "project
roots" or "root stylesheets" needs to be rethought because files at the
top of a CSS graph may not actually be the intended stylesheet —
especially when `@reference` is used. But… like anything… they also
_might be_.

In the meantime we'll "prefer" files we can detect as definite root
stylesheets before trying other files.

Author: thecrypticace

packages/tailwindcss-language-server/src/project-locator.test.ts

@@ -1,4 +1,4 @@
-import { expect, test } from 'vitest'
+import { expect, test, TestOptions } from 'vitest'
 import * as path from 'node:path'
 import { ProjectLocator } from './project-locator'
 import { URL, fileURLToPath } from 'url'
@@ -279,23 +279,68 @@ testLocator({
   ],
 })
 
+testLocator({
+  name: 'Roots are detected when they indirectly use Tailwind features',
+  fs: {
+    'package.json': json`
+      {
+        "dependencies": {
+          "tailwindcss": "4.0.6"
+        }
+      }
+    `,
+    // TODO: This is marked as the root which is… maybe fine but not sure
+    // The intention in this example is that src/globals.css is the real root
+    // but if src/articles.css suddenly gained `@theme` blocks then maybe it'd
+    // need to be the root instead.
+    'src/articles/articles.css': css`
+      @reference "../globals.css";
+      .article-title {
+        @apply text-primary;
+      }
+    `,
+    'src/articles/layout.js': js`
+      import "./articles.css";
+      export default function Layout(children) {
+        return children;
+      }
+    `,
+    'src/globals.css': scss`
+      @import "tailwindcss";
+      @theme {
+        --color-primary: #3490dc;
+      }
+    `,
+  },
+  expected: [
+    {
+      version: '4.0.6',
+      config: '/src/articles/articles.css',
+      content: [],
+    },
+  ],
+})
+
 // ---
 
 function testLocator({
   name,
   fs,
   expected,
   settings,
+  options,
 }: {
   name: string
   fs: Storage
   settings?: Partial<Settings>
   expected: any[]
+  options?: TestOptions
 }) {
   defineTest({
     name,
     fs,
     prepare,
+    options,
     async handle({ search }) {
       let projects = await search(settings)
 

packages/tailwindcss-language-server/src/project-locator.ts

@@ -427,11 +427,18 @@ export class ProjectLocator {
     if (indexPath && themePath) graph.connect(indexPath, themePath)
     if (indexPath && utilitiesPath) graph.connect(indexPath, utilitiesPath)
 
-    for (let root of graph.roots()) {
-      if (!root.meta) continue
+    // Sort the graph so potential "roots" appear first
+    // The entire concept of roots needs to be rethought because it's not always
+    // clear what the root of a project is. Even when imports are present a file
+    // may import a file that is the actual "root" of the project.
+    let roots = Array.from(graph.roots())
+
+    roots.sort((a, b) => {
+      return a.meta.root === b.meta.root ? 0 : a.meta.root ? -1 : 1
+    })
 
-      // This file is not eligible to act as a root of the CSS graph
-      if (root.meta.root === false) continue
+    for (let root of roots) {
+      if (!root.meta) continue
 
       let config: ConfigEntry = configs.remember(root.path, () => ({
         source: 'css',

packages/vscode-tailwindcss/CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## Prerelease
 
-- Nothing yet!
+- Fix detection when project contains stylesheets that import the "main" stylesheet ([#1218](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1218))
 
 ## 0.14.5