Add variant prefix to last class in a selector, not the first

__tests__/responsiveAtRule.test.js

@@ -0,0 +1,245 @@
+import postcss from 'postcss'
+import plugin from '../src/lib/substituteResponsiveAtRules'
+import config from '../defaultConfig.stub.js'
+
+function run(input, opts = () => config) {
+  return postcss([plugin(opts)]).process(input, { from: undefined })
+}
+
+test('it can generate responsive variants', () => {
+  const input = `
+    @responsive {
+      .banana { color: yellow; }
+      .chocolate { color: brown; }
+    }
+  `
+
+  const output = `
+      .banana { color: yellow; }
+      .chocolate { color: brown; }
+      @media (min-width: 500px) {
+        .sm\\:banana { color: yellow; }
+        .sm\\:chocolate { color: brown; }
+      }
+      @media (min-width: 750px) {
+        .md\\:banana { color: yellow; }
+        .md\\:chocolate { color: brown; }
+      }
+      @media (min-width: 1000px) {
+        .lg\\:banana { color: yellow; }
+        .lg\\:chocolate { color: brown; }
+      }
+  `
+
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: ':',
+    },
+  })).then(result => {
+    expect(result.css).toMatchCss(output)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
+test('it can generate responsive variants with a custom separator', () => {
+  const input = `
+    @responsive {
+      .banana { color: yellow; }
+      .chocolate { color: brown; }
+    }
+  `
+
+  const output = `
+      .banana { color: yellow; }
+      .chocolate { color: brown; }
+      @media (min-width: 500px) {
+        .sm__banana { color: yellow; }
+        .sm__chocolate { color: brown; }
+      }
+      @media (min-width: 750px) {
+        .md__banana { color: yellow; }
+        .md__chocolate { color: brown; }
+      }
+      @media (min-width: 1000px) {
+        .lg__banana { color: yellow; }
+        .lg__chocolate { color: brown; }
+      }
+  `
+
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: '__',
+    },
+  })).then(result => {
+    expect(result.css).toMatchCss(output)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
+test('responsive variants are grouped', () => {
+  const input = `
+    @responsive {
+      .banana { color: yellow; }
+    }
+
+    .apple { color: red; }
+
+    @responsive {
+      .chocolate { color: brown; }
+    }
+  `
+
+  const output = `
+      .banana { color: yellow; }
+      .apple { color: red; }
+      .chocolate { color: brown; }
+      @media (min-width: 500px) {
+        .sm\\:banana { color: yellow; }
+        .sm\\:chocolate { color: brown; }
+      }
+      @media (min-width: 750px) {
+        .md\\:banana { color: yellow; }
+        .md\\:chocolate { color: brown; }
+      }
+      @media (min-width: 1000px) {
+        .lg\\:banana { color: yellow; }
+        .lg\\:chocolate { color: brown; }
+      }
+  `
+
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: ':',
+    },
+  })).then(result => {
+    expect(result.css).toMatchCss(output)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
+test('screen prefix is only applied to the last class in a selector', () => {
+  const input = `
+    @responsive {
+      .banana li * .sandwich #foo > div { color: yellow; }
+    }
+  `
+
+  const output = `
+      .banana li * .sandwich #foo > div { color: yellow; }
+      @media (min-width: 500px) {
+        .banana li * .sm\\:sandwich #foo > div { color: yellow; }
+      }
+      @media (min-width: 750px) {
+        .banana li * .md\\:sandwich #foo > div { color: yellow; }
+      }
+      @media (min-width: 1000px) {
+        .banana li * .lg\\:sandwich #foo > div { color: yellow; }
+      }
+  `
+
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: ':',
+    },
+  })).then(result => {
+    expect(result.css).toMatchCss(output)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
+test('responsive variants are generated for all selectors in a rule', () => {
+  const input = `
+    @responsive {
+      .foo, .bar { color: yellow; }
+    }
+  `
+
+  const output = `
+      .foo, .bar { color: yellow; }
+      @media (min-width: 500px) {
+        .sm\\:foo, .sm\\:bar { color: yellow; }
+      }
+      @media (min-width: 750px) {
+        .md\\:foo, .md\\:bar { color: yellow; }
+      }
+      @media (min-width: 1000px) {
+        .lg\\:foo, .lg\\:bar { color: yellow; }
+      }
+  `
+
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: ':',
+    },
+  })).then(result => {
+    expect(result.css).toMatchCss(output)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
+test('selectors with no classes cannot be made responsive', () => {
+  const input = `
+    @responsive {
+      div { color: yellow; }
+    }
+  `
+  expect.assertions(1)
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: ':',
+    },
+  })).catch(e => {
+    expect(e).toMatchObject({ name: 'CssSyntaxError' })
+  })
+})
+
+test('all selectors in a rule must contain classes', () => {
+  const input = `
+    @responsive {
+      .foo, div { color: yellow; }
+    }
+  `
+  expect.assertions(1)
+  return run(input, () => ({
+    screens: {
+      sm: '500px',
+      md: '750px',
+      lg: '1000px',
+    },
+    options: {
+      separator: ':',
+    },
+  })).catch(e => {
+    expect(e).toMatchObject({ name: 'CssSyntaxError' })
+  })
+})

src/lib/substituteResponsiveAtRules.js

@@ -2,7 +2,7 @@ import _ from 'lodash'
 import postcss from 'postcss'
 import cloneNodes from '../util/cloneNodes'
 import buildMediaQuery from '../util/buildMediaQuery'
-import buildClassVariant from '../util/buildClassVariant'
+import buildSelectorVariant from '../util/buildSelectorVariant'
 
 export default function(config) {
   return function(css) {
@@ -28,7 +28,9 @@ export default function(config) {
         responsiveRules.map(rule => {
           const cloned = rule.clone()
           cloned.selectors = _.map(rule.selectors, selector =>
-            buildClassVariant(selector, screen, separator)
+            buildSelectorVariant(selector, screen, separator, message => {
+              throw rule.error(message)
+            })
           )
           return cloned
         })

src/lib/substituteVariantsAtRules.js

@@ -1,9 +1,9 @@
 import _ from 'lodash'
 import postcss from 'postcss'
-import buildClassVariant from '../util/buildClassVariant'
+import buildSelectorVariant from '../util/buildSelectorVariant'
 
 function buildPseudoClassVariant(selector, pseudoClass, separator) {
-  return `${buildClassVariant(selector, pseudoClass, separator)}:${pseudoClass}`
+  return `${buildSelectorVariant(selector, pseudoClass, separator)}:${pseudoClass}`
 }
 
 function generatePseudoClassVariant(pseudoClass) {
@@ -23,7 +23,11 @@ const variantGenerators = {
     const cloned = container.clone()
 
     cloned.walkRules(rule => {
-      rule.selector = `.group:hover ${buildClassVariant(rule.selector, 'group-hover', separator)}`
+      rule.selector = `.group:hover ${buildSelectorVariant(
+        rule.selector,
+        'group-hover',
+        separator
+      )}`
     })
 
     container.before(cloned.nodes)

src/util/buildSelectorVariant.js

@@ -0,0 +1,16 @@
+import escapeClassName from './escapeClassName'
+import parser from 'postcss-selector-parser'
+import tap from 'lodash/tap'
+
+export default function buildSelectorVariant(selector, variantName, separator, onError = () => {}) {
+  return parser(selectors => {
+    tap(selectors.first.filter(({ type }) => type === 'class').pop(), classSelector => {
+      if (classSelector === undefined) {
+        onError('Variant cannot be generated because selector contains no classes.')
+        return
+      }
+
+      classSelector.value = `${variantName}${escapeClassName(separator)}${classSelector.value}`
+    })
+  }).processSync(selector)
+}