Only emit utility/component variants when those layers exist

CHANGELOG.md

@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Show warnings for invalid content config ([#7065](https://github.com/tailwindlabs/tailwindcss/pull/7065))
 
+### Fixed
+
+- Only emit utility/component variants when those layers exist ([#7066](https://github.com/tailwindlabs/tailwindcss/pull/7066))
+
 ## [3.0.13] - 2022-01-11
 
 ### Fixed

src/lib/expandTailwindAtRules.js

@@ -205,9 +205,6 @@ export default function expandTailwindAtRules(context) {
 
     if (layerNodes.base) {
       layerNodes.base.before(cloneNodes([...baseNodes, ...defaultNodes], layerNodes.base.source))
-    }
-
-    if (layerNodes.base) {
       layerNodes.base.remove()
     }
 
@@ -221,16 +218,34 @@ export default function expandTailwindAtRules(context) {
       layerNodes.utilities.remove()
     }
 
+    // We do post-filtering to not alter the emitted order of the variants
+    const variantNodes = Array.from(screenNodes).filter((node) => {
+      const parentLayer = node.raws.tailwind?.parentLayer
+
+      if (parentLayer === 'components') {
+        return layerNodes.components !== null
+      }
+
+      if (parentLayer === 'utilities') {
+        return layerNodes.utilities !== null
+      }
+
+      return true
+    })
+
     if (layerNodes.variants) {
-      layerNodes.variants.before(cloneNodes([...screenNodes], layerNodes.variants.source))
+      layerNodes.variants.before(cloneNodes(variantNodes, layerNodes.variants.source))
       layerNodes.variants.remove()
-    } else {
-      root.append(cloneNodes([...screenNodes], root.source))
+    } else if (variantNodes.length > 0) {
+      root.append(cloneNodes(variantNodes, root.source))
     }
 
     // If we've got a utility layer and no utilities are generated there's likely something wrong
-    // TODO: Detect utility variants only
-    if (layerNodes.utilities && utilityNodes.size === 0 && screenNodes.size === 0) {
+    const hasUtilityVariants = variantNodes.some(
+      (node) => node.raws.tailwind?.parentLayer === 'utilities'
+    )
+
+    if (layerNodes.utilities && utilityNodes.size === 0 && !hasUtilityVariants) {
       log.warn('content-problems', [
         'No utilities were generated there is likely a problem with the `content` key in the tailwind config. For more information see the documentation: https://tailwindcss.com/docs/content-configuration',
       ])

src/lib/generateRules.js

@@ -216,6 +216,12 @@ function applyVariant(variant, matches, context) {
           })
         }
 
+        // This tracks the originating layer for the variant
+        // For example:
+        // .sm:underline {} is a variant of something in the utilities layer
+        // .sm:container {} is a variant of the container component
+        clone.nodes[0].raws.tailwind = { parentLayer: meta.layer }
+
         let withOffset = [
           {
             ...meta,

tests/variants.test.js

@@ -1,7 +1,7 @@
 import fs from 'fs'
 import path from 'path'
 
-import { run, css, html } from './util/run'
+import { run, css, html, defaults } from './util/run'
 
 test('variants', () => {
   let config = {
@@ -467,3 +467,75 @@ it('should be possible to use responsive modifiers that are defined with special
     `)
   })
 })
+
+it('including just the base layer should not produce variants', () => {
+  let config = {
+    content: [{ raw: html`<div class="sm:container sm:underline"></div>` }],
+    corePlugins: { preflight: false },
+  }
+
+  return run('@tailwind base', config).then((result) => {
+    return expect(result.css).toMatchFormattedCss(
+      css`
+        ${defaults}
+      `
+    )
+  })
+})
+
+it('variants for components should not be produced in a file without a components layer', () => {
+  let config = {
+    content: [{ raw: html`<div class="sm:container sm:underline"></div>` }],
+  }
+
+  return run('@tailwind utilities', config).then((result) => {
+    return expect(result.css).toMatchFormattedCss(css`
+      @media (min-width: 640px) {
+        .sm\:underline {
+          text-decoration-line: underline;
+        }
+      }
+    `)
+  })
+})
+
+it('variants for utilities should not be produced in a file without a utilities layer', () => {
+  let config = {
+    content: [{ raw: html`<div class="sm:container sm:underline"></div>` }],
+  }
+
+  return run('@tailwind components', config).then((result) => {
+    return expect(result.css).toMatchFormattedCss(css`
+      @media (min-width: 640px) {
+        .sm\:container {
+          width: 100%;
+        }
+        @media (min-width: 640px) {
+          .sm\:container {
+            max-width: 640px;
+          }
+        }
+        @media (min-width: 768px) {
+          .sm\:container {
+            max-width: 768px;
+          }
+        }
+        @media (min-width: 1024px) {
+          .sm\:container {
+            max-width: 1024px;
+          }
+        }
+        @media (min-width: 1280px) {
+          .sm\:container {
+            max-width: 1280px;
+          }
+        }
+        @media (min-width: 1536px) {
+          .sm\:container {
+            max-width: 1536px;
+          }
+        }
+      }
+    `)
+  })
+})