Suggest default variant values when they also support arbitrary values (#1439)

Given the following plugin:
```js
matchVariant('foo', (value) => ':is(' + value + ')', {
  values: {
    DEFAULT: 'default',
    a: 'a',
  }
})
```

We wouldn't suggest `foo:` as a variant even though it works. This is
because we were suggesting the arbitrary `foo-[]:` *or* the default
variant instead of both if a variant supported arbitrary values in v4.

This PR fixes the above and now both will be suggested.

Author: thecrypticace

packages/tailwindcss-language-server/tests/completions/completions.test.js

@@ -1082,3 +1082,72 @@ defineTest({
     expect(Object.fromEntries(requests)).toEqual(map)
   },
 })
+
+defineTest({
+  name: 'Completions show for variants that support default values *and* arbitrary values',
+  fs: {
+    'app.css': css`
+      @import 'tailwindcss';
+      @plugin "./plugin.js";
+    `,
+    'plugin.js': js`
+      export default function ({ matchVariant }) {
+        matchVariant('foo', (value) => ':is(' + value + ')', {
+          values: {
+            DEFAULT: 'default',
+            a: 'a',
+          }
+        })
+
+        matchVariant('bar', (value) => {
+          if (!value) return []
+          return ':is(' + value + ')'
+        }, {
+          values: {
+            a: 'a',
+          }
+        })
+      }
+    `,
+  },
+  prepare: async ({ root }) => ({ client: await createClient({ root }) }),
+  handle: async ({ client }) => {
+    let document = await client.open({
+      lang: 'html',
+      text: html`<div class=""></div>`,
+    })
+
+    // <div class=""></div>
+    //            ^
+    let list = await document.completions({ line: 0, character: 12 })
+    let items = list?.items ?? []
+
+    // The default version of this variant is suggested
+    let item1 = items.find((item) => item.label.startsWith('foo:'))
+    expect(item1?.detail).toEqual(':is(default)')
+
+    // As are any values
+    // TODO: This test requires Tailwind CSS v4.1.13
+    // let item2 = items.find((item) => item.label.startsWith('foo-a:'))
+    // expect(item2?.detail).toEqual(':is(a)')
+
+    // Ditto with arbitrary values
+    let item3 = items.find((item) => item.label.startsWith('foo-[]:'))
+    expect(item3).toBeDefined()
+    expect(item3?.detail).toEqual(undefined)
+
+    // This variant doesn't have a default so it's omitted
+    let item4 = items.find((item) => item.label.startsWith('bar:'))
+    expect(item4).not.toBeDefined()
+
+    // But does have a value so it is
+    // TODO: This test requires Tailwind CSS v4.1.13
+    // let item5 = items.find((item) => item.label.startsWith('bar-a:'))
+    // expect(item5?.detail).toEqual(':is(a)')
+
+    // And it supports arbitrary values so it should be as well
+    let item6 = items.find((item) => item.label.startsWith('bar-[]:'))
+    expect(item6).toBeDefined()
+    expect(item6?.detail).toEqual(undefined)
+  },
+})

packages/tailwindcss-language-service/src/completionProvider.ts

@@ -188,24 +188,36 @@ export function completionsFromClassList(
             // },
           }),
         )
-      } else {
-        let resultingVariants = [...existingVariants, variant.name]
+      }
 
-        let selectors: string[] = []
+      let hasDefault = false
+      let resultingVariants = [...existingVariants, variant.name]
 
-        try {
-          selectors = variant.selectors()
-        } catch (err) {
-          // If the selectors function fails we don't want to crash the whole completion process
-          console.log('Error while trying to get selectors for variant')
-          console.log({
-            variant,
-            err,
-          })
+      let selectors: string[] = []
 
-          continue
-        }
+      try {
+        selectors = variant.selectors()
+        hasDefault = true
+      } catch (err) {
+        // If the selectors function fails we don't want to crash the whole completion process
+        console.log('Error while trying to get selectors for variant')
+        console.log({
+          variant,
+          err,
+        })
+
+        continue
+      }
 
+      // Commentary:
+      // The check for `selectors.length` was previously omitted because of the `force` variant that
+      // existed before the v4.0 release. It was used to place a utility after other base utilities
+      // and before any using variants. It was dropped before v4.0. An empty selector set is a good
+      // marker for "this outputs nothing" and as such should be omitted from suggestions.
+      //
+      // This does mean that the force variant won't be suggested if IntelliSense is used with
+      // earlier pre-release versions but this is fine.
+      if (hasDefault && selectors.length > 0) {
         items.push(
           variantItem({
             label: `${variant.name}${sep}`,

packages/vscode-tailwindcss/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Prerelease
 
 - Publish our fork of the CSS language server ([#1437](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1437))
+- Suggest default variant values when they also support arbitrary values ([#1439](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/1439))
 
 ## 0.14.26