[Update] Make vue/max-attributes-per-line fixable

lib/rules/max-attributes-per-line.js

@@ -9,14 +9,16 @@
 // ------------------------------------------------------------------------------
 const utils = require('../utils')
 
+const LT_CHAR = /[\r\n\u2028\u2029]/
+
 module.exports = {
   meta: {
     docs: {
       description: 'enforce the maximum number of attributes per line',
       category: 'strongly-recommended',
       url: 'https://github.com/vuejs/eslint-plugin-vue/blob/v4.2.2/docs/rules/max-attributes-per-line.md'
     },
-    fixable: null,
+    fixable: 'whitespace', // or "code" or "whitespace"
     schema: [
       {
         type: 'object',
@@ -70,6 +72,7 @@ module.exports = {
     const multilineMaximum = configuration.multiline
     const singlelinemMaximum = configuration.singleline
     const canHaveFirstLine = configuration.allowFirstLine
+    const sourceCode = context.getSourceCode()
 
     return utils.defineTemplateBodyVisitor(context, {
       'VStartTag' (node) {
@@ -129,14 +132,24 @@ module.exports = {
     }
 
     function showErrors (attributes, node) {
-      attributes.forEach((prop) => {
+      attributes.forEach((prop, i) => {
         context.report({
           node: prop,
           loc: prop.loc,
           message: 'Attribute "{{propName}}" should be on a new line.',
           data: {
             propName: prop.key.name
-          }
+          },
+          fix: i === 0 ? (fixer) => {
+            let indent = getIndentText(prop)
+            const last = indent[indent.length - 1]
+            if (indent[indent.length - 1] === '\t') {
+              indent += '\t'
+            } else {
+              indent += last + last
+            }
+            return fixer.insertTextBefore(prop, `\n${indent}`)
+          } : undefined
         })
       })
     }
@@ -155,5 +168,20 @@ module.exports = {
 
       return propsPerLine
     }
+
+    function getIndentText (node) {
+      const text = sourceCode.text
+      let indentStart = node.range[0] - 1
+      while (indentStart >= 0 && !LT_CHAR.test(text[indentStart])) {
+        indentStart -= 1
+      }
+      let indentEnd = indentStart + 1
+
+      while (!text[indentEnd].trim()) {
+        indentEnd += 1
+      }
+
+      return text.slice(indentStart + 1, indentEnd)
+    }
   }
 }