Extract rule: template-no-html-comments

Author: NullVoxPopuli

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-html-comments](docs/rules/template-no-html-comments.md)                                   | disallow HTML comments in templates                             |    | 🔧 |    |
 | [template-no-log](docs/rules/template-no-log.md)                                                       | disallow {{log}} in templates                                   |    |    |    |
 
 ### Components

docs/rules/template-no-html-comments.md

@@ -0,0 +1,36 @@
+# ember/template-no-html-comments
+
+🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).
+
+<!-- end auto-generated rule header -->
+
+Disallow HTML comments in templates. HTML comments will be visible in the rendered output, which may expose sensitive information or clutter the DOM.
+
+## Rule Details
+
+This rule disallows HTML comments (`<!-- -->`) in templates and suggests using Glimmer comments (`{{! }}` or `{{!-- --}}`) instead.
+
+## Examples
+
+Examples of **incorrect** code for this rule:
+
+```gjs
+<template>
+  <!-- This is an HTML comment -->
+  <div>Content</div>
+</template>
+```
+
+Examples of **correct** code for this rule:
+
+```gjs
+<template>
+  {{! This is a Glimmer comment }}
+  <div>Content</div>
+</template>
+
+<template>
+  {{!-- This is a block Glimmer comment --}}
+  <div>Content</div>
+</template>
+```

lib/rules/template-no-html-comments.js

@@ -0,0 +1,57 @@
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description: 'disallow HTML comments in templates',
+      category: 'Best Practices',
+      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-html-comments.md',
+    },
+    fixable: 'code',
+    schema: [],
+    messages: {
+      noHtmlComments:
+        'HTML comments should not be used in templates. Use Handlebars comments instead.',
+    },
+    strictGjs: true,
+    strictGts: true,
+  },
+
+  create(context) {
+    return {
+      'Program:exit'(node) {
+        // Check for HTML comments in the source text
+        const sourceCode = context.sourceCode || context.getSourceCode();
+        const text = sourceCode.getText(node);
+
+        // Find all HTML comments in template blocks
+        const htmlCommentRegex = /<!--([\S\s]*?)-->/g;
+        let match;
+
+        while ((match = htmlCommentRegex.exec(text)) !== null) {
+          // Check if this comment is within a template
+          const beforeComment = text.slice(0, match.index);
+          const templateStart = beforeComment.lastIndexOf('<template>');
+          const templateEnd = text.indexOf('</template>', match.index);
+
+          if (templateStart !== -1 && templateEnd !== -1) {
+            const commentContent = match[1];
+            const startIndex = match.index;
+            const endIndex = match.index + match[0].length;
+
+            context.report({
+              loc: {
+                start: sourceCode.getLocFromIndex(startIndex),
+                end: sourceCode.getLocFromIndex(endIndex),
+              },
+              messageId: 'noHtmlComments',
+              fix(fixer) {
+                return fixer.replaceTextRange([startIndex, endIndex], `{{!${commentContent}}}`);
+              },
+            });
+          }
+        }
+      },
+    };
+  },
+};

tests/lib/rules/template-no-html-comments.js

@@ -0,0 +1,42 @@
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const rule = require('../../../lib/rules/template-no-html-comments');
+const RuleTester = require('eslint').RuleTester;
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+ruleTester.run('template-no-html-comments', rule, {
+  valid: [
+    '<template>{{! This is a comment }}</template>',
+    '<template>{{!-- This is a comment --}}</template>',
+    '<template><div>Content</div></template>',
+
+    // Test cases ported from ember-template-lint
+    '<template>{{!-- comment here --}}</template>',
+    '<template>{{!--comment here--}}</template>',
+  ],
+  invalid: [
+    {
+      code: '<template><!-- HTML comment --></template>',
+      output: '<template>{{! HTML comment }}</template>',
+      errors: [{ messageId: 'noHtmlComments' }],
+    },
+
+    // Test cases ported from ember-template-lint
+    {
+      code: '<template><!-- comment here --></template>',
+      output: '<template>{{! comment here }}</template>',
+      errors: [{ messageId: 'noHtmlComments' }],
+    },
+    {
+      code: '<template><!--comment here--></template>',
+      output: '<template>{{!comment here}}</template>',
+      errors: [{ messageId: 'noHtmlComments' }],
+    },
+  ],
+});