Hide internal fields from completions in matchUtilities (#18820)

The `__CSS_VALUES__` field is an internal field we use to transport data
about theme options from CSS throug hte JS plugin API. It wasn’t
supposed to show up in suggestions but we forgot to remove it from them.

Fixes #18812

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Discard matched variants with non-string values ([#18799](https://github.com/tailwindlabs/tailwindcss/pull/18799))
 - Show suggestions for known `matchVariant` values ([#18798](https://github.com/tailwindlabs/tailwindcss/pull/18798))
 - Replace deprecated `clip` with `clip-path` in `sr-only` ([#18769](https://github.com/tailwindlabs/tailwindcss/pull/18769))
+- Hide internal fields from completions in `matchUtilities` ([#18820](https://github.com/tailwindlabs/tailwindcss/pull/18820))
 - Upgrade: Migrate `aria` theme keys to `@custom-variant` ([#18815](https://github.com/tailwindlabs/tailwindcss/pull/18815))
 - Upgrade: Migrate `data` theme keys to `@custom-variant` ([#18816](https://github.com/tailwindlabs/tailwindcss/pull/18816))
 - Upgrade: Migrate `supports` theme keys to `@custom-variant` ([#18817](https://github.com/tailwindlabs/tailwindcss/pull/18817))

packages/tailwindcss/src/compat/plugin-api.ts

@@ -472,6 +472,10 @@ export function buildPluginApi({
           // work even with legacy configs and plugins
           valueKeys.delete('__BARE_VALUE__')
 
+          // The `__CSS_VALUES__` key is a special key used by the theme function
+          // to transport `@theme` metadata about values from CSS
+          valueKeys.delete('__CSS_VALUES__')
+
           // The `DEFAULT` key is represented as `null` in the utility API
           if (valueKeys.has('DEFAULT')) {
             valueKeys.delete('DEFAULT')

packages/tailwindcss/src/intellisense.test.ts

@@ -712,3 +712,38 @@ test('matchVariant', async () => {
   expect(v1.name).toEqual('foo')
   expect(v1.values).toEqual(['a', 'b'])
 })
+
+test('matchUtilities discards internal only helpers from suggestions when using the theme function', async () => {
+  let input = css`
+    @import 'tailwindcss/utilities';
+    @plugin "./plugin.js";
+
+    @theme {
+      --color-red: red;
+    }
+  `
+
+  let design = await __unstable__loadDesignSystem(input, {
+    loadStylesheet: async (_, base) => ({
+      path: '',
+      base,
+      content: '@tailwind utilities;',
+    }),
+    loadModule: async () => ({
+      path: '',
+      base: '',
+      module: plugin(({ matchUtilities, theme }) => {
+        matchUtilities({ foo: (val) => ({ color: val }) }, { values: theme('colors') })
+        matchUtilities({ bar: (val) => ({ color: val }) }, { values: theme('transitionDuration') })
+      }),
+    }),
+  })
+
+  let classNames = design.getClassList().map((e) => e[0])
+
+  expect(classNames).not.toContain('foo-__BARE_VALUE__')
+  expect(classNames).not.toContain('bar-__BARE_VALUE__')
+
+  expect(classNames).not.toContain('foo-__CSS_VALUES__')
+  expect(classNames).not.toContain('bar-__CSS_VALUES__')
+})