Extract rule: template-no-inline-event-handlers

README.md

@@ -203,6 +203,7 @@ rules in templates can be disabled with eslint directives with mustache or html
 | [template-no-chained-this](docs/rules/template-no-chained-this.md)                                     | disallow redundant `this.this` in templates                     |    | 🔧 |    |
 | [template-no-debugger](docs/rules/template-no-debugger.md)                                             | disallow {{debugger}} in templates                              |    |    |    |
 | [template-no-element-event-actions](docs/rules/template-no-element-event-actions.md)                   | disallow element event actions (use {{on}} modifier instead)    |    |    |    |
+| [template-no-inline-event-handlers](docs/rules/template-no-inline-event-handlers.md)                   | disallow DOM event handler attributes                           |    |    |    |
 | [template-no-inline-styles](docs/rules/template-no-inline-styles.md)                                   | disallow inline styles                                          |    |    |    |
 | [template-no-input-placeholder](docs/rules/template-no-input-placeholder.md)                           | disallow placeholder attribute on input elements                |    |    |    |
 | [template-no-input-tagname](docs/rules/template-no-input-tagname.md)                                   | disallow tagName attribute on {{input}} helper                  |    |    |    |

docs/rules/template-no-inline-event-handlers.md

@@ -0,0 +1,72 @@
+# ember/template-no-inline-event-handlers
+
+<!-- end auto-generated rule header -->
+
+Disallows DOM event handler attributes in templates.
+
+Inline event handlers like `onclick="..."` are an older pattern that should be replaced with the `{{on}}` modifier for better Ember integration and testability.
+
+## Rule Details
+
+This rule disallows the use of inline DOM event handler attributes like `onclick`, `onsubmit`, etc.
+
+## Examples
+
+Examples of **incorrect** code for this rule:
+
+```gjs
+<template>
+  <button onclick="alert('test')">Click</button>
+</template>
+```
+
+```gjs
+<template>
+  <div onmousedown="handleEvent()">Content</div>
+</template>
+```
+
+```gjs
+<template>
+  <form onsubmit="return false;">Form</form>
+</template>
+```
+
+Examples of **correct** code for this rule:
+
+```gjs
+<template>
+  <button {{on "click" this.handleClick}}>Click</button>
+</template>
+```
+
+```gjs
+<template>
+  <input {{on "input" this.handleInput}} />
+</template>
+```
+
+```gjs
+<template>
+  <form {{on "submit" this.handleSubmit}}>Form</form>
+</template>
+```
+
+## Migration
+
+Replace:
+
+```gjs
+<button onclick="alert('clicked')">
+```
+
+With:
+
+```gjs
+<button {{on "click" this.handleClick}}>
+```
+
+## References
+
+- [Ember.js Guides - Event Handling](https://guides.emberjs.com/release/components/component-state-and-actions/)
+- [eslint-plugin-ember template-no-inline-styles](https://github.com/ember-cli/eslint-plugin-ember/blob/master/docs/rules/template-no-inline-styles.md)

lib/rules/template-no-inline-event-handlers.js

@@ -0,0 +1,58 @@
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow DOM event handler attributes',
+      category: 'Best Practices',
+      strictGjs: true,
+      strictGts: true,
+      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-inline-event-handlers.md',
+    },
+    fixable: null,
+    schema: [],
+    messages: {
+      unexpected:
+        'Do not use inline event handlers like "{{name}}". Use the (on) modifier instead.',
+    },
+  },
+
+  create(context) {
+    const EVENT_HANDLER_ATTRS = new Set([
+      'onclick',
+      'ondblclick',
+      'onmousedown',
+      'onmouseup',
+      'onmousemove',
+      'onmouseout',
+      'onmouseover',
+      'onkeydown',
+      'onkeyup',
+      'onkeypress',
+      'onchange',
+      'oninput',
+      'onsubmit',
+      'onfocus',
+      'onblur',
+      'onload',
+      'onerror',
+      'onscroll',
+    ]);
+
+    return {
+      GlimmerElementNode(node) {
+        if (node.attributes) {
+          for (const attr of node.attributes) {
+            if (attr.name && EVENT_HANDLER_ATTRS.has(attr.name.toLowerCase())) {
+              context.report({
+                node: attr,
+                messageId: 'unexpected',
+                data: { name: attr.name },
+              });
+            }
+          }
+        }
+      },
+    };
+  },
+};

tests/lib/rules/template-no-inline-event-handlers.js

@@ -0,0 +1,71 @@
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const rule = require('../../../lib/rules/template-no-inline-event-handlers');
+const RuleTester = require('eslint').RuleTester;
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+ruleTester.run('template-no-inline-event-handlers', rule, {
+  valid: [
+    `<template>
+      <button {{on "click" this.handleClick}}>Click</button>
+    </template>`,
+    `<template>
+      <input {{on "input" this.handleInput}} />
+    </template>`,
+    `<template>
+      <div>No handlers</div>
+    </template>`,
+  ],
+
+  invalid: [
+    {
+      code: `<template>
+        <button onclick="alert('test')">Click</button>
+      </template>`,
+      output: null,
+      errors: [
+        {
+          message:
+            'Do not use inline event handlers like "onclick". Use the (on) modifier instead.',
+          type: 'GlimmerAttrNode',
+        },
+      ],
+    },
+    {
+      code: `<template>
+        <div onmousedown="handleEvent()">Content</div>
+      </template>`,
+      output: null,
+      errors: [
+        {
+          message:
+            'Do not use inline event handlers like "onmousedown". Use the (on) modifier instead.',
+          type: 'GlimmerAttrNode',
+        },
+      ],
+    },
+    {
+      code: `<template>
+        <form onsubmit="return false;">Form</form>
+      </template>`,
+      output: null,
+      errors: [
+        {
+          message:
+            'Do not use inline event handlers like "onsubmit". Use the (on) modifier instead.',
+          type: 'GlimmerAttrNode',
+        },
+      ],
+    },
+  ],
+});