Extract rule: template-no-forbidden-elements

NullVoxPopuli · NullVoxPopuli · commit 92d4939f3948 · 2026-02-23T15:00:38.000-05:00
diff --git a/README.md b/README.md
@@ -199,6 +199,7 @@ rules in templates can be disabled with eslint directives with mustache or html
 | [template-no-capital-arguments](docs/rules/template-no-capital-arguments.md)                           | disallow capital arguments (use lowercase @arg instead of @Arg) |    |    |    |
 | [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-forbidden-elements](docs/rules/template-no-forbidden-elements.md)                         | disallow specific HTML elements                                 |    |    |    |
 | [template-no-log](docs/rules/template-no-log.md)                                                       | disallow {{log}} in templates                                   |    |    |    |
 
 ### Components
diff --git a/docs/rules/template-no-forbidden-elements.md b/docs/rules/template-no-forbidden-elements.md
@@ -0,0 +1,53 @@
+# ember/template-no-forbidden-elements
+
+<!-- end auto-generated rule header -->
+
+This rule disallows the use of forbidden elements in template files.
+
+The rule is configurable so teams can add their own disallowed elements.
+The default list of forbidden elements are `meta`, `html`, and `script`.
+
+## Examples
+
+This rule **forbids** the following:
+
+```gjs
+<template><script></script></template>
+```
+
+```gjs
+<template><html></html></template>
+```
+
+```gjs
+<template><meta charset='utf-8' /></template>
+```
+
+This rule **allows** the following:
+
+```gjs
+<template><header></header></template>
+```
+
+```gjs
+<template><div></div></template>
+```
+
+```gjs
+<template>
+  <head>
+    <meta charset='utf-8' />
+  </head>
+</template>
+```
+
+Note: `<meta>` inside `<head>` is allowed as an exception.
+
+## Configuration
+
+- `boolean` — `true` to enable with defaults / `false` to disable
+- `string[]` — an array of element names to forbid (default: `['meta', 'html', 'script']`)
+
+## References
+
+- [Ember guides/template restrictions](https://guides.emberjs.com/release/components/#toc_restrictions)
diff --git a/lib/rules/template-no-forbidden-elements.js b/lib/rules/template-no-forbidden-elements.js
@@ -0,0 +1,58 @@
+const DEFAULT_FORBIDDEN = ['meta', 'html', 'script'];
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'disallow specific HTML elements',
+      category: 'Best Practices',
+      recommendedGjs: false,
+      recommendedGts: false,
+      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-forbidden-elements.md',
+    },
+    schema: [
+      {
+        oneOf: [{ type: 'array', items: { type: 'string' } }, { type: 'boolean' }],
+      },
+    ],
+    messages: { forbidden: 'Use of forbidden element <{{element}}>' },
+  },
+  create(context) {
+    const rawConfig = context.options[0];
+    let forbiddenList;
+
+    if (rawConfig === true || rawConfig === undefined) {
+      forbiddenList = DEFAULT_FORBIDDEN;
+    } else if (Array.isArray(rawConfig)) {
+      forbiddenList = rawConfig;
+    } else {
+      forbiddenList = [];
+    }
+
+    const forbidden = new Set(forbiddenList);
+
+    // Track element stack for <meta> in <head> exception
+    const elementStack = [];
+
+    return {
+      GlimmerElementNode(node) {
+        elementStack.push(node.tag);
+
+        if (!forbidden.has(node.tag)) {
+          return;
+        }
+
+        // Exception: <meta> inside <head> is allowed
+        if (node.tag === 'meta' && elementStack.includes('head')) {
+          return;
+        }
+
+        context.report({ node, messageId: 'forbidden', data: { element: node.tag } });
+      },
+      'GlimmerElementNode:exit'() {
+        elementStack.pop();
+      },
+    };
+  },
+};
diff --git a/tests/lib/rules/template-no-forbidden-elements.js b/tests/lib/rules/template-no-forbidden-elements.js
@@ -0,0 +1,47 @@
+const rule = require('../../../lib/rules/template-no-forbidden-elements');
+const RuleTester = require('eslint').RuleTester;
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+ruleTester.run('template-no-forbidden-elements', rule, {
+  valid: [
+    { code: '<template><div></div></template>', options: [['script']] },
+    // Test cases ported from ember-template-lint
+    '<template><header></header></template>',
+    '<template><footer></footer></template>',
+    '<template><p></p></template>',
+    '<template><head><meta charset="utf-8"></head></template>',
+  ],
+  invalid: [
+    {
+      code: '<template><script></script></template>',
+      output: null,
+      options: [['script']],
+      errors: [{ messageId: 'forbidden' }],
+    },
+
+    // Test cases ported from ember-template-lint
+    {
+      code: '<template><html></html></template>',
+      output: null,
+      errors: [{ messageId: 'forbidden' }],
+    },
+    {
+      code: '<template><style></style></template>',
+      output: null,
+      errors: [{ messageId: 'forbidden' }],
+    },
+    {
+      code: '<template><meta charset="utf-8"></template>',
+      output: null,
+      errors: [{ messageId: 'forbidden' }],
+    },
+    {
+      code: '<template><head><html></html></head></template>',
+      output: null,
+      errors: [{ messageId: 'forbidden' }],
+    },
+  ],
+});
