split @apply values by spaces, tabs and newlines

Fixes: #2222

__tests__/applyComplexClasses.test.js

@@ -47,6 +47,53 @@ test('it copies class declarations into itself', () => {
   })
 })
 
+test('apply values can contain tabs', () => {
+  const input = `
+    .a {
+      @apply p-4\tm-4;
+    }
+  `
+
+  const expected = `
+    .a {
+      margin: 1rem;
+      padding: 1rem;
+    }
+  `
+
+  expect.assertions(2)
+
+  return run(input).then(result => {
+    expect(result.css).toMatchCss(expected)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
+test('apply values can contain newlines', () => {
+  const input = `
+    .a {
+      @apply p-4 m-4
+      flex flex-col;
+    }
+  `
+
+  const expected = `
+    .a {
+      display: flex;
+      flex-direction: column;
+      margin: 1rem;
+      padding: 1rem;
+    }
+  `
+
+  expect.assertions(2)
+
+  return run(input).then(result => {
+    expect(result.css).toMatchCss(expected)
+    expect(result.warnings().length).toBe(0)
+  })
+})
+
 test('selectors with invalid characters do not need to be manually escaped', () => {
   const input = `
     .a\\:1\\/2 { color: red; }

src/flagged/applyComplexClasses.js

@@ -200,7 +200,7 @@ function processApplyAtRules(css, lookupTree, config) {
           importantEntries,
           applyUtilityNames,
           important = importantEntries.length > 0,
-        ] = _.partition(applyRule.params.split(' '), n => n === '!important')
+        ] = _.partition(applyRule.params.split(/[\s\t\n]+/g), n => n === '!important')
 
         const currentUtilityNames = extractUtilityNames(rule.selector)