Use resolveThemeValue API

The one we have actually works for what we want

Author: thecrypticace

packages/tailwindcss-language-server/src/util/v4/design-system.ts

@@ -172,25 +172,6 @@ export async function loadDesignSystem(
         ? postcss.root({ nodes }).toString().trim()
         : nodes.toString().trim()
     },
-
-    lookupThemeValue(themeKey: string): string | null {
-      if (!themeKey.startsWith('--')) {
-        return null
-      }
-
-      let details = design.theme.values.get(themeKey)
-
-      // That theme key doesn't exist
-      if (!details) return null
-
-      // Early versions of v4 had string values
-      if (typeof details === 'string') {
-        return details
-      }
-
-      // Later versions have an object with more data
-      return details.value
-    }
   })
 
   return design

packages/tailwindcss-language-service/src/util/css-vars.test.ts

@@ -11,7 +11,7 @@ test('replacing CSS variables with their fallbacks (when they have them)', () =>
   let state: State = {
     enabled: true,
     designSystem: {
-      lookupThemeValue: (name) => map.get(name) ?? null,
+      resolveThemeValue: (name) => map.get(name) ?? null,
     } as DesignSystem,
   }
 

packages/tailwindcss-language-service/src/util/css-vars.ts

@@ -8,8 +8,8 @@ export function replaceCssVarsWithFallbacks(state: State, str: string): string {
     // In a v4 project we should attempt to look up the value from the theme
     // this is because not all v4 projects will generate utilities where
     // variables have fallbacks
-    if (state.designSystem) {
-      return state.designSystem.lookupThemeValue(name)
+    if (state.designSystem && name.startsWith('--')) {
+      return state.designSystem.resolveThemeValue?.(name) ?? null
     }
 
     // Don't replace the variable otherwise

packages/tailwindcss-language-service/src/util/v4/design-system.ts

@@ -43,5 +43,7 @@ export interface DesignSystem {
 export interface DesignSystem {
   compile(classes: string[]): postcss.Root[]
   toCss(nodes: postcss.Root | postcss.Node[]): string
-  lookupThemeValue(themeKey: string): string | null
+
+  // Optional because it did not exist in earlier v4 alpha versions
+  resolveThemeValue?(path: string): string | null
 }