feat: add fixable, no more error when unused variable with prefix _

docs/rules/README.md

@@ -48,7 +48,7 @@ Enforce all the rules in this category, as well as all higher priority rules, wi
 | [vue/no-template-key](./no-template-key.md) | disallow `key` attribute on `<template>` |  |
 | [vue/no-textarea-mustache](./no-textarea-mustache.md) | disallow mustaches in `<textarea>` |  |
 | [vue/no-unused-components](./no-unused-components.md) | disallow registering components that are not used inside templates |  |
-| [vue/no-unused-vars](./no-unused-vars.md) | disallow unused variable definitions of v-for directives or scope attributes |  |
+| [vue/no-unused-vars](./no-unused-vars.md) | disallow unused variable definitions of v-for directives or scope attributes | :wrench: |
 | [vue/no-use-v-if-with-v-for](./no-use-v-if-with-v-for.md) | disallow use v-if on the same element as v-for |  |
 | [vue/require-component-is](./require-component-is.md) | require `v-bind:is` of `<component>` elements |  |
 | [vue/require-prop-type-constructor](./require-prop-type-constructor.md) | require prop type to be a constructor | :wrench: |

docs/rules/no-unused-vars.md

@@ -8,12 +8,13 @@ description: disallow unused variable definitions of v-for directives or scope a
 > disallow unused variable definitions of v-for directives or scope attributes
 
 - :gear: This rule is included in all of `"plugin:vue/essential"`, `"plugin:vue/strongly-recommended"` and `"plugin:vue/recommended"`.
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
 
 ## :book: Rule Details
 
 This rule report variable definitions of v-for directives or scope attributes if those are not used.
 
-<eslint-code-block :rules="{'vue/no-unused-vars': ['error']}">
+<eslint-code-block fix :rules="{'vue/no-unused-vars': ['error']}">
 
 ```vue
 <template>

lib/rules/no-unused-vars.js

@@ -18,26 +18,49 @@ module.exports = {
       category: 'essential',
       url: 'https://eslint.vuejs.org/rules/no-unused-vars.html'
     },
-    fixable: null,
-    schema: []
+    fixable: 'code',
+    schema: [
+      {
+        'type': 'object',
+        'properties': {
+          'varIgnorePattern': {
+            'type': 'string'
+          }
+        },
+        'additionalProperties': false
+      }
+    ]
   },
 
   create (context) {
+    const option = context.options[0] || { varIgnorePattern: '^_' }
+    const pattern = option['varIgnorePattern'] || '^_'
+    // only use for construct a regularExpression
+    // eslint-disable-next-line no-eval
+    const regExp = eval(`/${pattern}/`)
     return utils.defineTemplateBodyVisitor(context, {
       VElement (node) {
         const variables = node.variables
 
         for (
           let i = variables.length - 1;
-          i >= 0 && !variables[i].references.length;
+          i >= 0 && !regExp.test(variables[i].id.name) && !variables[i].references.length;
           i--
         ) {
           const variable = variables[i]
           context.report({
             node: variable.id,
             loc: variable.id.loc,
             message: `'{{name}}' is defined but never used.`,
-            data: variable.id
+            data: variable.id,
+            suggest: [
+              {
+                desc: 'Replace the unused-var with default ignore pattern',
+                fix: function (fixer) {
+                  return fixer.replaceText(variable.id, `_${variable.id.name}`)
+                }
+              }
+            ]
           })
         }
       }

tests/lib/rules/no-unused-vars.js

@@ -52,6 +52,22 @@ tester.run('no-unused-vars', rule, {
     },
     {
       code: '<template><div v-for="x in foo" :[x]></div></template>'
+    },
+    {
+      code: '<template><div v-for="_ in foo" ></div></template>',
+      options: [{ varIgnorePattern: '^_' }]
+
+    },
+    {
+      code: '<template><div v-for="_i in foo" ></div></template>'
+    },
+    {
+      code: '<template><div v-for="ignorei in foo" ></div></template>',
+      options: [{ varIgnorePattern: '^ignore' }]
+    },
+    {
+      code: '<template><div v-for="thisisignore in foo" ></div></template>',
+      options: [{ varIgnorePattern: 'ignore$' }]
     }
   ],
   invalid: [
@@ -82,6 +98,7 @@ tester.run('no-unused-vars', rule, {
     {
       code: '<template><div v-for="(a, b, c) in foo"></div></template>',
       errors: ["'a' is defined but never used.", "'b' is defined but never used.", "'c' is defined but never used."]
+
     },
     {
       code: '<template><div v-for="(a, b, c) in foo">{{a}}</div></template>',
@@ -98,6 +115,21 @@ tester.run('no-unused-vars', rule, {
     {
       code: '<template><div v-for="x in items">{{value | x}}</div></template>',
       errors: ["'x' is defined but never used."]
+    },
+    {
+      code: '<template><div v-for="x in items">{{value}}</div></template>',
+      options: [{ varIgnorePattern: 'ignore$' }],
+      errors: ["'x' is defined but never used."]
+    },
+    {
+      code: '<template><span slot-scope="props"></span></template>',
+      errors: ["'props' is defined but never used."],
+      options: [{ varIgnorePattern: '^ignore' }]
+    },
+    {
+      code: '<template><span><template scope="props"></template></span></template>',
+      errors: ["'props' is defined but never used."],
+      options: [{ varIgnorePattern: '^ignore' }]
     }
   ]
 })