Add dark mode variant option

src/corePlugins.js

@@ -225,12 +225,26 @@ export let variantPlugins = {
         'Change `darkMode` to `media` or remove it entirely.',
         'https://tailwindcss.com/docs/upgrade-guide#remove-dark-mode-configuration',
       ])
+    } else if (mode === 'variant' && className === '.dark') {
+      mode = false
+      log.warn('darkmode-variant-without-selector', [
+        'darkMode: "variant" was used without a provided selector.',
+        'Change to `darkMode: ["variant", ".your-selector &"]` ',
+      ])
+    } else if (mode === 'variant' && !className.includes('&')) {
+      mode = false
+      log.warn('darkmode-variant-without-ampersand', [
+        'A custom dark mode selector was used without an `&` — a `&` is required to correctly scope the custom selector.',
+        'Change to `darkMode: ["variant", ".your-selector &"]` ',
+      ])
     }
 
     if (mode === 'class') {
       addVariant('dark', `:is(:where(${className}) &)`)
     } else if (mode === 'media') {
       addVariant('dark', '@media (prefers-color-scheme: dark)')
+    } else if (mode === 'variant') {
+      addVariant('dark', className)
     }
   },
 

tests/dark-mode.test.js

@@ -119,3 +119,26 @@ it('should default to the `media` mode when mode is set to `false`', () => {
     `)
   })
 })
+
+it('should allow customization of the dark mode variant', () => {
+  let config = {
+    darkMode: ['variant', '&:not(.light *)'],
+    content: [{ raw: html`<div class="dark:font-bold"></div>` }],
+    corePlugins: { preflight: false },
+  }
+
+  let input = css`
+    @tailwind base;
+    @tailwind components;
+    @tailwind utilities;
+  `
+
+  return run(input, config).then((result) => {
+    expect(result.css).toMatchFormattedCss(css`
+      ${defaults}
+      .dark\:font-bold:not(.light *) {
+        font-weight: 700;
+      }
+    `)
+  })
+})

types/config.d.ts

@@ -75,6 +75,8 @@ type DarkModeConfig =
   | 'class'
   // Use the `class` strategy with a custom class instead of `.dark`.
   | ['class', string]
+  // Use the `variant` strategy, which allows you to completely customize the selector
+  | ['variant', string]
 
 type Screen = { raw: string } | { min: string } | { max: string } | { min: string; max: string }
 type ScreensConfig = string[] | KeyValuePair<string, string | Screen | Screen[]>