Implement the supports variant (#9453)

* implement a `supports` variant

* update changelog

* use `--tw` instead of `--tw-empty`

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add `@config` support ([#9405](https://github.com/tailwindlabs/tailwindcss/pull/9405))
 - Add `fill-none` and `stroke-none` utilities by default ([#9403](https://github.com/tailwindlabs/tailwindcss/pull/9403))
 - Support `sort` function in `matchVariant` ([#9423](https://github.com/tailwindlabs/tailwindcss/pull/9423))
+- Implement the `supports` variant ([#9453](https://github.com/tailwindlabs/tailwindcss/pull/9453))
 
 ### Fixed
 

src/corePlugins.js

@@ -16,6 +16,7 @@ import { normalizeScreens } from './util/normalizeScreens'
 import { formatBoxShadowValue, parseBoxShadowValue } from './util/parseBoxShadowValue'
 import { removeAlphaVariables } from './util/removeAlphaVariables'
 import { flagEnabled } from './featureFlags'
+import { normalize } from './util/dataTypes'
 
 export let variantPlugins = {
   pseudoElementVariants: ({ addVariant }) => {
@@ -215,6 +216,37 @@ export let variantPlugins = {
     }
   },
 
+  supportsVariants: ({ matchVariant, theme, config }) => {
+    if (!flagEnabled(config(), 'matchVariant')) return
+
+    matchVariant(
+      'supports',
+      ({ value = '' }) => {
+        let check = normalize(value)
+        let isRaw = /^\w*\s*\(/.test(check)
+
+        // Chrome has a bug where `(condtion1)or(condition2)` is not valid
+        // But `(condition1) or (condition2)` is supported.
+        check = isRaw ? check.replace(/\b(and|or|not)\b/g, ' $1 ') : check
+
+        if (isRaw) {
+          return `@supports ${check}`
+        }
+
+        if (!check.includes(':')) {
+          check = `${check}: var(--tw)`
+        }
+
+        if (!(check.startsWith('(') && check.endsWith(')'))) {
+          check = `(${check})`
+        }
+
+        return `@supports ${check} `
+      },
+      { values: theme('supports') ?? {} }
+    )
+  },
+
   orientationVariants: ({ addVariant }) => {
     addVariant('portrait', '@media (orientation: portrait)')
     addVariant('landscape', '@media (orientation: landscape)')

src/lib/setupContextUtils.js

@@ -655,6 +655,7 @@ function resolvePlugins(context, root) {
     variantPlugins['pseudoClassVariants'],
   ]
   let afterVariants = [
+    variantPlugins['supportsVariants'],
     variantPlugins['directionVariants'],
     variantPlugins['reducedMotionVariants'],
     variantPlugins['prefersContrastVariants'],

tests/arbitrary-variants.test.js

@@ -615,3 +615,95 @@ test('classes in the same arbitrary variant should not be prefixed', () => {
     `)
   })
 })
+
+it('should support supports', () => {
+  let config = {
+    experimental: { matchVariant: true },
+    theme: {
+      supports: {
+        grid: 'display: grid',
+      },
+    },
+    content: [
+      {
+        raw: html`
+          <div>
+            <!-- Property check -->
+            <div class="supports-[display:grid]:grid"></div>
+            <!-- Value with spaces, needs to be normalized -->
+            <div class="supports-[transform-origin:5%_5%]:underline"></div>
+            <!-- Selectors (raw) -->
+            <div class="supports-[selector(A>B)]:underline"></div>
+            <!-- 'not' check (raw) -->
+            <div class="supports-[not(foo:bar)]:underline"></div>
+            <!-- 'or' check (raw) -->
+            <div class="supports-[(foo:bar)or(bar:baz)]:underline"></div>
+            <!-- 'and' check (raw) -->
+            <div class="supports-[(foo:bar)and(bar:baz)]:underline"></div>
+            <!-- No value give for the property, defaulting to prop: var(--tw) -->
+            <div class="supports-[container-type]:underline"></div>
+            <!-- Named supports usage -->
+            <div class="supports-grid:underline"></div>
+          </div>
+        `,
+      },
+    ],
+    corePlugins: { preflight: false },
+  }
+
+  let input = css`
+    @tailwind utilities;
+  `
+
+  return run(input, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(css`
+      @supports (display: grid) {
+        .supports-grid\:underline {
+          text-decoration-line: underline;
+        }
+      }
+
+      @supports (display: grid) {
+        .supports-\[display\:grid\]\:grid {
+          display: grid;
+        }
+      }
+
+      @supports (transform-origin: 5% 5%) {
+        .supports-\[transform-origin\:5\%_5\%\]\:underline {
+          text-decoration-line: underline;
+        }
+      }
+
+      @supports selector(A > B) {
+        .supports-\[selector\(A\>B\)\]\:underline {
+          text-decoration-line: underline;
+        }
+      }
+
+      @supports not (foo: bar) {
+        .supports-\[not\(foo\:bar\)\]\:underline {
+          text-decoration-line: underline;
+        }
+      }
+
+      @supports (foo: bar) or (bar: baz) {
+        .supports-\[\(foo\:bar\)or\(bar\:baz\)\]\:underline {
+          text-decoration-line: underline;
+        }
+      }
+
+      @supports (foo: bar) and (bar: baz) {
+        .supports-\[\(foo\:bar\)and\(bar\:baz\)\]\:underline {
+          text-decoration-line: underline;
+        }
+      }
+
+      @supports (container-type: var(--tw)) {
+        .supports-\[container-type\]\:underline {
+          text-decoration-line: underline;
+        }
+      }
+    `)
+  })
+})