feat(v-on-handler-style): allow ["inline", "inline-function"] option

docs/rules/v-on-handler-style.md

@@ -47,7 +47,7 @@ This rule aims to enforce a consistent style in `v-on` event handlers:
 ```json
 {
   "vue/v-on-handler-style": ["error",
-    ["method", "inline-function"], // ["method", "inline-function"] | ["method", "inline"] | "inline-function" | "inline"
+    ["method", "inline-function"], // ["method", "inline-function"] | ["method", "inline"] | ["inline", "inline-function"] | "inline-function" | "inline"
     {
       "ignoreIncludesComment": false
     }
@@ -58,10 +58,12 @@ This rule aims to enforce a consistent style in `v-on` event handlers:
 - First option ... Specifies the name of an allowed style. Default is `["method", "inline-function"]`.
   - `["method", "inline-function"]` ... Allow handlers by method binding. e.g. `v-on:click="handler"`. Allow inline functions where method handlers cannot be used. e.g. `v-on:click="() => handler(listItem)"`.
   - `["method", "inline"]` ... Allow handlers by method binding. e.g. `v-on:click="handler"`. Allow inline handlers where method handlers cannot be used. e.g. `v-on:click="handler(listItem)"`.
+  - `["inline", "inline-function"]` ... Allow inline handlers. e.g. `v-on:click="handler()"`. Allow inline functions if they have at least 1 argument. e.g. `v-on:click="(arg1, arg2) => handler(arg1, arg2)"`.
   - `"inline-function"` ... Allow inline functions. e.g. `v-on:click="() => handler()"`
   - `"inline"` ... Allow inline handlers. e.g. `v-on:click="handler()"`
 - Second option
   - `ignoreIncludesComment` ... If `true`, do not report inline handlers or inline functions containing comments, even if the preferred style is `"method"`. Default is `false`.
+  - `allowInlineFuncSingleArg` ... Used in conjunction with `["method", "inline-function"]` or `["inline", "inline-function"]`. If `true`, allow inline functions with a single argument. Default is `false`.
 
 ### `["method", "inline-function"]` (Default)
 
@@ -121,6 +123,68 @@ This rule aims to enforce a consistent style in `v-on` event handlers:
 
 </eslint-code-block>
 
+### `["inline", "inline-function"]`
+
+<eslint-code-block fix :rules="{'vue/v-on-handler-style': ['error', ['inline', 'inline-function']]}">
+
+```vue
+<template>
+  <!-- ✓ GOOD -->
+  <button v-on:click="count++" />
+  <button v-on:click="handler()" />
+  <button v-on:click="handler($event)" />
+  <button v-on:click="(arg1, arg2) => handler(arg1, arg2)" />
+  <template v-for="e in list">
+    <button v-on:click="handler(e)" />
+    <button v-on:click="handler($event, e)" />
+    <button v-on:click="(arg1, arg2) => handler(arg1, arg2, e)" />
+  </template>
+
+  <!-- ✗ BAD -->
+  <button v-on:click="() => count++" />
+  <button v-on:click="handler" />
+  <button v-on:click="() => handler()" />
+  <button v-on:click="(arg) => handler(arg)" />
+  <template v-for="e in list">
+    <button v-on:click="() => handler(e)" />
+    <button v-on:click="(arg) => handler(arg, e)" />
+  </template>
+</template>
+```
+
+</eslint-code-block>
+
+### `["inline", "inline-function"]` with `allowInlineFuncSingleArg: true`
+
+<eslint-code-block fix :rules="{'vue/v-on-handler-style': ['error', ['inline', 'inline-function'], { allowInlineFuncSingleArg: true }]}">
+
+```vue
+<template>
+  <!-- ✓ GOOD -->
+  <button v-on:click="count++" />
+  <button v-on:click="handler()" />
+  <button v-on:click="handler($event)" />
+  <button v-on:click="(arg) => handler(arg)" />
+  <button v-on:click="(arg1, arg2) => handler(arg1, arg2)" />
+  <template v-for="e in list">
+    <button v-on:click="handler(e)" />
+    <button v-on:click="handler($event, e)" />
+    <button v-on:click="(arg) => handler(arg, e)" />
+    <button v-on:click="(arg1, arg2) => handler(arg1, arg2, e)" />
+  </template>
+
+  <!-- ✗ BAD -->
+  <button v-on:click="() => count++" />
+  <button v-on:click="handler" />
+  <button v-on:click="() => handler()" />
+  <template v-for="e in list">
+    <button v-on:click="() => handler(e)" />
+  </template>
+</template>
+```
+
+</eslint-code-block>
+
 ### `"inline-function"`
 
 <eslint-code-block fix :rules="{'vue/v-on-handler-style': ['error', 'inline-function']}">

lib/rules/v-on-handler-style.js

@@ -11,6 +11,7 @@ const utils = require('../utils')
  * @typedef {'method' | 'inline' | 'inline-function'} HandlerKind
  * @typedef {object} ObjectOption
  * @property {boolean} [ignoreIncludesComment]
+ * @property {boolean} [allowInlineFuncSingleArg]
  */
 
 /**
@@ -33,8 +34,9 @@ function parseOptions(context) {
 
   const option = options[1] || {}
   const ignoreIncludesComment = !!option.ignoreIncludesComment
+  const allowInlineFuncSingleArg = option.allowInlineFuncSingleArg === true
 
-  return { allows, ignoreIncludesComment }
+  return { allows, ignoreIncludesComment, allowInlineFuncSingleArg }
 }
 
 /**
@@ -112,33 +114,73 @@ module.exports = {
       url: 'https://eslint.vuejs.org/rules/v-on-handler-style.html'
     },
     fixable: 'code',
-    schema: [
-      {
-        oneOf: [
-          { enum: ['inline', 'inline-function'] },
-          {
-            type: 'array',
-            items: [
-              { const: 'method' },
-              { enum: ['inline', 'inline-function'] }
-            ],
-            uniqueItems: true,
-            additionalItems: false,
-            minItems: 2,
-            maxItems: 2
-          }
-        ]
-      },
-      {
-        type: 'object',
-        properties: {
-          ignoreIncludesComment: {
-            type: 'boolean'
-          }
+    schema: {
+      anyOf: [
+        // `inline`, `inline-function` or `['method', 'inline']`
+        {
+          type: 'array',
+          items: [
+            {
+              anyOf: [
+                { enum: ['inline', 'inline-function'] },
+                {
+                  type: 'array',
+                  items: [{ const: 'method' }, { const: 'inline' }],
+                  uniqueItems: true,
+                  additionalItems: false,
+                  minItems: 2,
+                  maxItems: 2
+                }
+              ]
+            },
+            {
+              type: 'object',
+              properties: {
+                ignoreIncludesComment: {
+                  type: 'boolean'
+                }
+              },
+              additionalProperties: false
+            }
+          ],
+          additionalItems: false,
+          minItems: 1,
+          maxItems: 2
         },
-        additionalProperties: false
-      }
-    ],
+        // `['method', 'inline-function']` or `['inline', 'inline-function']`
+        {
+          type: 'array',
+          items: [
+            {
+              type: 'array',
+              items: [
+                { enum: ['method', 'inline'] },
+                { const: 'inline-function' }
+              ],
+              uniqueItems: true,
+              additionalItems: false,
+              minItems: 2,
+              maxItems: 2
+            },
+            {
+              type: 'object',
+              properties: {
+                ignoreIncludesComment: {
+                  type: 'boolean'
+                },
+                allowInlineFuncSingleArg: {
+                  type: 'boolean'
+                }
+              },
+              additionalProperties: false
+            }
+          ],
+          additionalItems: false,
+          minItems: 0,
+          maxItems: 2
+        }
+      ]
+    },
     messages: {
       preferMethodOverInline:
         'Prefer method handler over inline handler in v-on.',
@@ -162,7 +204,8 @@ module.exports = {
   },
   /** @param {RuleContext} context */
   create(context) {
-    const { allows, ignoreIncludesComment } = parseOptions(context)
+    const { allows, ignoreIncludesComment, allowInlineFuncSingleArg } =
+      parseOptions(context)
 
     /** @type {Set<VElement>} */
     const upperElements = new Set()
@@ -530,6 +573,20 @@ module.exports = {
               if (allows[0] === 'inline-function') {
                 return
               }
+
+              if (allows[1] === 'inline-function') {
+                if (expression.params.length > 1) {
+                  return
+                }
+
+                if (
+                  expression.params.length === 1 &&
+                  allowInlineFuncSingleArg
+                ) {
+                  return
+                }
+              }
+
               for (const allow of allows) {
                 if (verifyForInlineFunction(expression, allow)) {
                   return