⭐️New: Add vue/v-on-parens rule

README.md

@@ -202,6 +202,7 @@ Enforce all the rules in this category, as well as all higher priority rules, wi
 |  | [vue/no-confusing-v-for-v-if](./docs/rules/no-confusing-v-for-v-if.md) | disallow confusing `v-for` and `v-if` on the same element |
 | :wrench: | [vue/order-in-components](./docs/rules/order-in-components.md) | enforce order of properties in components |
 |  | [vue/this-in-template](./docs/rules/this-in-template.md) | enforce usage of `this` in template |
+| :wrench: | [vue/v-on-parens](./docs/rules/v-on-parens.md) | enforce or forbid parentheses after method calls without arguments in `v-on` directives |
 
 ### Uncategorized
 

docs/rules/v-on-parens.md

@@ -0,0 +1,66 @@
+# enforce or forbid parentheses after method calls without arguments in `v-on` directives (vue/v-on-parens)
+
+- :gear: This rule is included in `"plugin:vue/recommended"`.
+- :wrench: The `--fix` option on the [command line](http://eslint.org/docs/user-guide/command-line-interface#fix) can automatically fix some of the problems reported by this rule.
+
+## :book: Rule Details
+
+:-1: Example of **incorrect** code for this rule:
+
+```html
+<button v-on:click="closeModal()">
+  Close
+</button>
+```
+
+:+1: Example of **correct** code for this rule:
+
+```html
+<button v-on:click="closeModal">
+  Close
+</button>
+```
+
+## :wrench: Options
+
+Default is set to `never`.
+
+```
+'vue/v-on-parens': [2, 'always'|'never']
+```
+
+### `"always"` - Always use parentheses in `v-on` directives
+
+:-1: Example of **incorrect** code:
+
+```html
+<button v-on:click="closeModal">
+  Close
+</button>
+```
+
+:+1: Example of **correct** code:
+
+```html
+<button v-on:click="closeModal()">
+  Close
+</button>
+```
+
+### `"never"` - Never use parentheses in `v-on` directives for method calls without arguments
+
+:-1: Example of **incorrect** code:
+
+```html
+<button v-on:click="closeModal()">
+  Close
+</button>
+```
+
+:+1: Example of **correct** code:
+
+```html
+<button v-on:click="closeModal">
+  Close
+</button>
+```

lib/configs/recommended.js

@@ -10,6 +10,7 @@ module.exports = {
     'vue/html-quotes': 'error',
     'vue/no-confusing-v-for-v-if': 'error',
     'vue/order-in-components': 'error',
-    'vue/this-in-template': 'error'
+    'vue/this-in-template': 'error',
+    'vue/v-on-parens': 'error'
   }
 }

lib/index.js

@@ -44,6 +44,7 @@ module.exports = {
     'script-indent': require('./rules/script-indent'),
     'this-in-template': require('./rules/this-in-template'),
     'v-bind-style': require('./rules/v-bind-style'),
+    'v-on-parens': require('./rules/v-on-parens'),
     'v-on-style': require('./rules/v-on-style'),
     'valid-template-root': require('./rules/valid-template-root'),
     'valid-v-bind': require('./rules/valid-v-bind'),

lib/rules/v-on-parens.js

@@ -0,0 +1,60 @@
+/**
+ * @author Niklas Higi
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const utils = require('../utils')
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'enforce or forbid parentheses after method calls without arguments in `v-on` directives',
+      category: 'recommended',
+      url: 'https://github.com/vuejs/eslint-plugin-vue/blob/v4.5.0/docs/rules/v-on-parens.md'
+    },
+    fixable: 'code',
+    schema: [
+      { enum: ['always', 'never'] }
+    ]
+  },
+
+  create (context) {
+    const always = context.options[0] === 'always'
+
+    return utils.defineTemplateBodyVisitor(context, {
+      "VAttribute[directive=true][key.name='on'][key.argument!=null] VOnExpression > ExpressionStatement > *" (node) {
+        const hasParens = node.type === 'CallExpression'
+        if (hasParens && node.arguments.length > 0) return
+
+        if (always && !hasParens) {
+          context.report({
+            node,
+            loc: node.loc,
+            message: "Method calls inside of 'v-on' directives must have parentheses.",
+            fix: fixer => fixer.insertTextAfter(node, '()')
+          })
+        } else if (!always && hasParens) {
+          context.report({
+            node,
+            loc: node.loc,
+            message: "Method calls without arguments inside of 'v-on' directives must not have parentheses.",
+            fix: fixer => {
+              const nodeString = context.getSourceCode().getText().substring(node.range[0], node.range[1])
+              // This ensures that parens are also removed if they contain whitespace
+              const parensLength = nodeString.match(/\(\s*\)\s*$/)[0].length
+              return fixer.removeRange([node.end - parensLength, node.end])
+            }
+          })
+        }
+      }
+    })
+  }
+}

tests/lib/rules/v-on-parens.js

@@ -0,0 +1,63 @@
+/**
+ * @author Niklas Higi
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const RuleTester = require('eslint').RuleTester
+const rule = require('../../../lib/rules/v-on-parens')
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+const tester = new RuleTester({
+  parser: 'vue-eslint-parser',
+  parserOptions: { ecmaVersion: 2015 }
+})
+
+tester.run('v-on-parens', rule, {
+  valid: [
+    {
+      filename: 'test.vue',
+      code: ''
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><div @click="foo(123)"></div></template>',
+      options: ['always']
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><div @click="foo(123)"></div></template>',
+      options: ['never']
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><div @click="foo()"></div></template>',
+      options: ['always']
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><div @click="foo"></div></template>',
+      options: ['never']
+    }
+  ],
+  invalid: [
+    {
+      filename: 'test.vue',
+      code: '<template><div @click="foo"></div></template>',
+      errors: ["Method calls inside of 'v-on' directives must have parentheses."],
+      options: ['always']
+    },
+    {
+      filename: 'test.vue',
+      code: '<template><div @click="foo()"></div></template>',
+      errors: ["Method calls without arguments inside of 'v-on' directives must not have parentheses."],
+      options: ['never']
+    }
+  ]
+})