correctly detect empty footnote definitions with only HTML comments

Author: TKDev7

docs/rules/no-empty-definitions.md

@@ -4,12 +4,16 @@ Disallow empty definitions.
 
 ## Background
 
-Markdown allows you to specify a label as a placeholder for a URL in both links and images using square brackets, such as:
+Markdown allows you to specify a label as a placeholder for a URL in both links and images, or as a footnote reference, using square brackets. For example:
 
 ```markdown
 [ESLint][eslint]
 
 [eslint]: https://eslint.org
+
+[ESLint][^eslint]
+
+[^eslint]: Find and fix problmes in your JavaScript code
 ```
 
 Definitions with an empty URL or only an empty fragment (`#`), as well as footnote definitions with no content, are usually mistakes and do not provide useful information.
@@ -58,7 +62,7 @@ Examples of **correct** code for this rule with `checkFootnoteDefinitions: false
 
 ## When Not to Use It
 
-If you aren't concerned with empty definitions or empty footnote definitions, you can safely disable this rule.
+If you aren't concerned with empty definitions, you can safely disable this rule.
 
 ## Prior Art
 

src/rules/no-empty-definitions.js

@@ -8,10 +8,29 @@
 //-----------------------------------------------------------------------------
 
 /**
- * @typedef {import("../types.ts").MarkdownRuleDefinition<{ RuleOptions: [{ checkFootnoteDefinitions?: boolean; }] }>}
- * NoEmptyDefinitionsRuleDefinition
+ * @import { MarkdownRuleDefinition } from "../types.js";
+ * @typedef {"emptyDefinition" | "emptyFootnoteDefinition"} NoEmptyDefinitionsMessageIds
+ * @typedef {[{ checkFootnoteDefinitions?: boolean }]} NoEmptyDefinitionsOptions
+ * @typedef {MarkdownRuleDefinition<{ RuleOptions: NoEmptyDefinitionsOptions, MessageIds: NoEmptyDefinitionsMessageIds }>} NoEmptyDefinitionsRuleDefinition
  */
 
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+const htmlCommentPattern = /<!--[\s\S]*?-->/gu;
+
+/**
+ * Checks if a string contains only HTML comments.
+ * @param {string} value The input string to check.
+ * @returns {boolean} True if the string contains only HTML comments, false otherwise.
+ */
+function isOnlyComments(value) {
+	const withoutComments = value.replace(htmlCommentPattern, "");
+
+	return withoutComments.trim().length === 0;
+}
+
 //-----------------------------------------------------------------------------
 // Rule Definition
 //-----------------------------------------------------------------------------
@@ -62,7 +81,15 @@ export default {
 			},
 
 			footnoteDefinition(node) {
-				if (checkFootnoteDefinitions && node.children.length === 0) {
+				if (
+					checkFootnoteDefinitions &&
+					(node.children.length === 0 ||
+						node.children.every(
+							child =>
+								child.type === "html" &&
+								isOnlyComments(child.value),
+						))
+				) {
 					context.report({
 						loc: node.position,
 						messageId: "emptyFootnoteDefinition",

tests/rules/no-empty-definitions.test.js

@@ -39,6 +39,14 @@ ruleTester.run("no-empty-definitions", rule, {
 		"[\\^note]:",
 		"[^note\\]:",
 		"[^note]\\:",
+		"[^foo]: <span></span> <!-- comment -->",
+		"[^foo]: content <!-- comment -->",
+		"[^foo]: <!-- comment --> content",
+		"[^foo]: <!-- comment --> content <!-- comment -->",
+		dedent`
+		[^foo]: <!-- comm
+		    ent --> content <!-- comment -->
+		`,
 		{
 			code: "[^note]:",
 			options: [{ checkFootnoteDefinitions: false }],
@@ -178,5 +186,45 @@ ruleTester.run("no-empty-definitions", rule, {
 				},
 			],
 		},
+		{
+			code: "[^foo]: <!-- comment -->",
+			errors: [
+				{
+					messageId: "emptyFootnoteDefinition",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 25,
+				},
+			],
+		},
+		{
+			code: dedent`
+			[^foo]: <!-- comment
+			    -->`,
+			errors: [
+				{
+					messageId: "emptyFootnoteDefinition",
+					line: 1,
+					column: 1,
+					endLine: 2,
+					endColumn: 8,
+				},
+			],
+		},
+		{
+			code: dedent`
+			[^foo]: <!-- comment -->
+			    <!-- another comment -->`,
+			errors: [
+				{
+					messageId: "emptyFootnoteDefinition",
+					line: 1,
+					column: 1,
+					endLine: 2,
+					endColumn: 29,
+				},
+			],
+		},
 	],
 });