Fix container names with hyphens (#17628)

Fixes #17614.

Candidate parsing for variants only account for the root `@` if there no
hyphens. It seems like the current logic assumes if it *does* have a
hyphen, then it would be one of `@min` or `@max`. However, with:

```css
@theme {
  --container-foo-bar: 1440px;
}
```
Then `@foo-bar` should be valid. However, we only check for `@foo-bar`
and `@foo` as roots, but never `@`. This PR adds a check for `@` at the
very end after iterating through root permutations.

---------

Co-authored-by: Philipp Spiess <hello@philippspiess.com>

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure `color-mix(…)` polyfills do not cause used CSS variables to be removed ([#17555](https://github.com/tailwindlabs/tailwindcss/pull/17555))
 - Ensure the `color-mix(…)` polyfill creates fallbacks for theme variables that reference other theme variables ([#17562](https://github.com/tailwindlabs/tailwindcss/pull/17562))
 - Fix brace expansion in `@source inline('z-{10..0}')` with range going down ([#17591](https://github.com/tailwindlabs/tailwindcss/pull/17591))
+- Ensure container query variant names can contain hyphens ([#17628](https://github.com/tailwindlabs/tailwindcss/pull/17628))
 
 ## [4.1.3] - 2025-04-04
 

packages/tailwindcss/src/candidate.test.ts

@@ -1294,6 +1294,36 @@ it('should parse a functional variant starting with @', () => {
   `)
 })
 
+it('should parse a functional variant starting with @ that has a hyphen', () => {
+  let utilities = new Utilities()
+  utilities.static('flex', () => [])
+
+  let variants = new Variants()
+  variants.functional('@', () => {})
+
+  expect(run('@foo-bar:flex', { utilities, variants })).toMatchInlineSnapshot(`
+    [
+      {
+        "important": false,
+        "kind": "static",
+        "raw": "@foo-bar:flex",
+        "root": "flex",
+        "variants": [
+          {
+            "kind": "functional",
+            "modifier": null,
+            "root": "@",
+            "value": {
+              "kind": "named",
+              "value": "foo-bar",
+            },
+          },
+        ],
+      },
+    ]
+  `)
+})
+
 it('should parse a functional variant starting with @ and a modifier', () => {
   let utilities = new Utilities()
   utilities.static('flex', () => [])

packages/tailwindcss/src/candidate.ts

@@ -745,14 +745,6 @@ function* findRoots(input: string, exists: (input: string) => boolean): Iterable
   // Otherwise test every permutation of the input by iteratively removing
   // everything after the last dash.
   let idx = input.lastIndexOf('-')
-  if (idx === -1) {
-    // Variants starting with `@` are special because they don't need a `-`
-    // after the `@` (E.g.: `@-lg` should be written as `@lg`).
-    if (input[0] === '@' && exists('@')) {
-      yield ['@', input.slice(1)]
-    }
-    return
-  }
 
   // Determine the root and value by testing permutations of the incoming input.
   //
@@ -761,7 +753,7 @@ function* findRoots(input: string, exists: (input: string) => boolean): Iterable
   // `bg-red-500` -> No match
   // `bg-red`     -> No match
   // `bg`         -> Match
-  do {
+  while (idx > 0) {
     let maybeRoot = input.slice(0, idx)
 
     if (exists(maybeRoot)) {
@@ -776,5 +768,11 @@ function* findRoots(input: string, exists: (input: string) => boolean): Iterable
     }
 
     idx = input.lastIndexOf('-', idx - 1)
-  } while (idx > 0)
+  }
+
+  // Try '@' variant after permutations. This allows things like `@max` of `@max-foo-bar`
+  // to match before looking for `@`.
+  if (input[0] === '@' && exists('@')) {
+    yield ['@', input.slice(1)]
+  }
 }

packages/tailwindcss/src/variants.test.ts

@@ -2074,6 +2074,7 @@ test('container queries', async () => {
       css`
         @theme {
           --container-lg: 1024px;
+          --container-foo-bar: 1440px;
         }
         @tailwind utilities;
       `,
@@ -2082,20 +2083,38 @@ test('container queries', async () => {
         '@lg/name:flex',
         '@[123px]:flex',
         '@[456px]/name:flex',
+        '@foo-bar:flex',
+        '@foo-bar/name:flex',
 
         '@min-lg:flex',
         '@min-lg/name:flex',
         '@min-[123px]:flex',
         '@min-[456px]/name:flex',
+        '@min-foo-bar:flex',
+        '@min-foo-bar/name:flex',
 
         '@max-lg:flex',
         '@max-lg/name:flex',
         '@max-[123px]:flex',
         '@max-[456px]/name:flex',
+        '@max-foo-bar:flex',
+        '@max-foo-bar/name:flex',
       ],
     ),
   ).toMatchInlineSnapshot(`
-    "@container name not (min-width: 1024px) {
+    "@container name not (min-width: 1440px) {
+      .\\@max-foo-bar\\/name\\:flex {
+        display: flex;
+      }
+    }
+
+    @container not (min-width: 1440px) {
+      .\\@max-foo-bar\\:flex {
+        display: flex;
+      }
+    }
+
+    @container name not (min-width: 1024px) {
       .\\@max-lg\\/name\\:flex {
         display: flex;
       }
@@ -2153,6 +2172,30 @@ test('container queries', async () => {
       .\\@min-lg\\:flex {
         display: flex;
       }
+    }
+
+    @container name (min-width: 1440px) {
+      .\\@foo-bar\\/name\\:flex {
+        display: flex;
+      }
+    }
+
+    @container (min-width: 1440px) {
+      .\\@foo-bar\\:flex {
+        display: flex;
+      }
+    }
+
+    @container name (min-width: 1440px) {
+      .\\@min-foo-bar\\/name\\:flex {
+        display: flex;
+      }
+    }
+
+    @container (min-width: 1440px) {
+      .\\@min-foo-bar\\:flex {
+        display: flex;
+      }
     }"
   `)
 })