Don't create v4 projects for CSS files that don't look like v4 configs

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

@@ -16,6 +16,7 @@ import { extractSourceDirectives, resolveCssImports } from './css'
 import { normalizeDriveLetter, normalizePath, pathToFileURL } from './utils'
 import postcss from 'postcss'
 import * as oxide from './oxide'
+import { guessTailwindVersion, TailwindVersion } from './version-guesser'
 
 export interface ProjectConfig {
   /** The folder that contains the project */
@@ -130,6 +131,8 @@ export class ProjectLocator {
   private async createProject(config: ConfigEntry): Promise<ProjectConfig | null> {
     let tailwind = await this.detectTailwindVersion(config)
 
+    let possibleVersions = config.entries.flatMap((entry) => entry.versions)
+
     console.log(
       JSON.stringify({
         tailwind,
@@ -160,6 +163,15 @@ export class ProjectLocator {
         return null
       }
 
+      // This config doesn't include any v4 features (even ones that were also in v3)
+      if (!possibleVersions.includes('4')) {
+        console.warn(
+          `The config ${config.path} looks like it might be for a different Tailwind CSS version. Skipping.`,
+        )
+
+        return null
+      }
+
       // v4 does not support .sass, .scss, .less, and .styl files as configs
       if (requiresPreprocessor(config.path)) {
         console.warn(
@@ -324,15 +336,19 @@ export class ProjectLocator {
     // Read the content of all the CSS files
     await Promise.all(css.map((entry) => entry.read()))
 
+    // Determine what tailwind versions each file might be using
+    await Promise.all(css.map((entry) => entry.resolvePossibleVersions()))
+
     // Keep track of files that might import or involve Tailwind in some way
     let imports: FileEntry[] = []
 
     for (let file of css) {
       // If the CSS file couldn't be read for some reason, skip it
       if (!file.content) continue
 
-      // Look for `@import`, `@tailwind`, `@theme`, `@config`, etc…
-      if (!file.isMaybeTailwindRelated()) continue
+      // This file doesn't appear to use Tailwind CSS nor any imports
+      // so we can skip it
+      if (file.versions.length === 0) continue
 
       // Find `@config` directives in CSS files and resolve them to the actual
       // config file that they point to. This is only relevant for v3 which
@@ -642,6 +658,7 @@ class FileEntry {
   deps: FileEntry[] = []
   realpath: string | null
   sources: string[] = []
+  versions: TailwindVersion[] = []
 
   constructor(
     public type: 'js' | 'css',
@@ -709,6 +726,13 @@ class FileEntry {
     }
   }
 
+  /**
+   * Determine which Tailwind versions this file might be using
+   */
+  async resolvePossibleVersions() {
+    this.versions = this.content ? guessTailwindVersion(this.content) : []
+  }
+
   /**
    * Look for `@config` directives in a CSS file and return the path to the config
    * file that it points to. This path is (possibly) relative to the CSS file so
@@ -727,25 +751,6 @@ class FileEntry {
 
     return normalizePath(path.resolve(path.dirname(this.path), match.groups.config.slice(1, -1)))
   }
-
-  /**
-   * Look for tailwind-specific directives in a CSS file. This means that it
-   * participates in the CSS "graph" for the project and we need to traverse
-   * the graph to find all the CSS files that are considered entrypoints.
-   */
-  isMaybeTailwindRelated(): boolean {
-    if (!this.content) return false
-
-    let HAS_IMPORT = /@import\s*['"]/
-    let HAS_TAILWIND = /@tailwind\s*[^;]+;/
-    let HAS_DIRECTIVE = /@(theme|plugin|config|utility|variant|apply)\s*[^;{]+[;{]/
-
-    return (
-      HAS_IMPORT.test(this.content) ||
-      HAS_TAILWIND.test(this.content) ||
-      HAS_DIRECTIVE.test(this.content)
-    )
-  }
 }
 
 function requiresPreprocessor(filepath: string) {

packages/tailwindcss-language-server/src/version-guesser.ts

@@ -0,0 +1,53 @@
+export type TailwindVersion = '3' | '4'
+
+/**
+ * Determine the likely Tailwind version used by the given file
+ *
+ * This returns an array of possible versions, as a file could contain
+ * features that make determining the version ambiguous.
+ *
+ * The order *does* matter, as the first item is the most likely version.
+ */
+export function guessTailwindVersion(content: string): TailwindVersion[] {
+  // It's likely this is a v4 file if it has a v4 import:
+  // - `@import "tailwindcss"`
+  // - `@import "tailwindcss/theme"
+  // - etc…
+  let HAS_V4_IMPORT = /@import\s*['"]tailwindcss(?:\/[^'"]+)?['"]/
+  if (HAS_V4_IMPORT.test(content)) return ['4']
+
+  // It's likely this is a v4 file if it has a v4-specific feature:
+  // - @theme
+  // - @plugin
+  // - @utility
+  // - @variant
+  // - @custom-variant
+  let HAS_V4_DIRECTIVE = /@(theme|plugin|utility|custom-variant|variant|reference)\s*[^;{]+[;{]/
+  if (HAS_V4_DIRECTIVE.test(content)) return ['4']
+
+  // It's likely this is a v4 file if it's using v4's custom functions:
+  // - --alpha(…)
+  // - --spacing(…)
+  // - --theme(…)
+  let HAS_V4_FN = /--(alpha|spacing|theme)\(/
+  if (HAS_V4_FN.test(content)) return ['4']
+
+  // If the file contains older `@tailwind` directives, it's likely a v3 file
+  let HAS_LEGACY_TAILWIND = /@tailwind\s*(base|preflight|components|variants|screens)+;/
+  if (HAS_LEGACY_TAILWIND.test(content)) return ['3']
+
+  // If the file contains other `@tailwind` directives it might be either
+  let HAS_TAILWIND = /@tailwind\s*[^;]+;/
+  if (HAS_TAILWIND.test(content)) return ['4', '3']
+
+  // If the file contains other `@apply` or `@config` it might be either
+  let HAS_COMMON_DIRECTIVE = /@(config|apply)\s*[^;{]+[;{]/
+  if (HAS_COMMON_DIRECTIVE.test(content)) return ['4', '3']
+
+  // If it's got imports at all it could be either
+  let HAS_IMPORT = /@import\s*['"]/
+  if (HAS_IMPORT.test(content)) return ['4', '3']
+
+  // There's chance this file isn't tailwind-related
+  return []
+}

packages/tailwindcss-language-server/tests/env/v4.test.js

@@ -225,3 +225,122 @@ defineTest({
     expect(completion.items.length).toBe(12288)
   },
 })
+
+defineTest({
+  name: 'v4, uses npm, does not detect v3 config files as possible roots',
+  fs: {
+    'package.json': json`
+      {
+        "dependencies": {
+          "tailwindcss": "4.0.1"
+        }
+      }
+    `,
+    // This file MUST be before the v4 CSS file when sorting alphabetically
+    '_globals.css': css`
+      @tailwind base;
+      @tailwind utilities;
+      @tailwind components;
+    `,
+    'app.css': css`
+      @import 'tailwindcss';
+
+      @theme {
+        --color-primary: #c0ffee;
+      }
+    `,
+  },
+  prepare: async ({ root }) => ({ c: await init(root) }),
+  handle: async ({ c }) => {
+    let textDocument = await c.openDocument({
+      lang: 'html',
+      text: '<div class="bg-primary">',
+    })
+
+    expect(c.project).toMatchObject({
+      tailwind: {
+        version: '4.0.1',
+        isDefaultVersion: false,
+      },
+    })
+
+    let hover = await c.sendRequest(HoverRequest.type, {
+      textDocument,
+
+      // <div class="bg-primary">
+      //             ^
+      position: { line: 0, character: 13 },
+    })
+
+    expect(hover).toEqual({
+      contents: {
+        language: 'css',
+        value: dedent`
+          .bg-primary {
+            background-color: var(--color-primary) /* #c0ffee */;
+          }
+        `,
+      },
+      range: {
+        start: { line: 0, character: 12 },
+        end: { line: 0, character: 22 },
+      },
+    })
+  },
+})
+
+defineTest({
+  name: 'v4, uses fallback, does not detect v3 config files as possible roots',
+  fs: {
+    // This file MUST be before the v4 CSS file when sorting alphabetically
+    '_globals.css': css`
+      @tailwind base;
+      @tailwind utilities;
+      @tailwind components;
+    `,
+    'app.css': css`
+      @import 'tailwindcss';
+
+      @theme {
+        --color-primary: #c0ffee;
+      }
+    `,
+  },
+  prepare: async ({ root }) => ({ c: await init(root) }),
+  handle: async ({ c }) => {
+    let textDocument = await c.openDocument({
+      lang: 'html',
+      text: '<div class="bg-primary">',
+    })
+
+    expect(c.project).toMatchObject({
+      tailwind: {
+        version: '4.0.0',
+        isDefaultVersion: true,
+      },
+    })
+
+    let hover = await c.sendRequest(HoverRequest.type, {
+      textDocument,
+
+      // <div class="bg-primary">
+      //             ^
+      position: { line: 0, character: 13 },
+    })
+
+    expect(hover).toEqual({
+      contents: {
+        language: 'css',
+        value: dedent`
+          .bg-primary {
+            background-color: var(--color-primary) /* #c0ffee */;
+          }
+        `,
+      },
+      range: {
+        start: { line: 0, character: 12 },
+        end: { line: 0, character: 22 },
+      },
+    })
+  },
+})

packages/vscode-tailwindcss/CHANGELOG.md

@@ -5,6 +5,7 @@
 - Allow v4.0 projects not installed with npm to use IntelliSense ([#1157](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1157))
 - Ignore preprocessor files when looking for v4 configs ([#1159](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1159))
 - Allow language service to be used in native ESM environments ([#1122](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1122))
+- Don't create v4 projects for CSS files that don't look like v4 configs [#1164](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1164)
 
 ## 0.14.2