feat: add no-emphasis-as-heading rule

README.md

@@ -111,6 +111,7 @@ export default defineConfig([
 | [`no-bare-urls`](./docs/rules/no-bare-urls.md)                                 | Disallow bare URLs                                                                                |       no        |
 | [`no-duplicate-definitions`](./docs/rules/no-duplicate-definitions.md)         | Disallow duplicate definitions                                                                    |       yes       |
 | [`no-duplicate-headings`](./docs/rules/no-duplicate-headings.md)               | Disallow duplicate headings in the same document                                                  |       no        |
+| [`no-emphasis-as-heading`](./docs/rules/no-emphasis-as-heading.md)             | Disallow using fully bolded paragraphs as headings                                                |       yes       |
 | [`no-empty-definitions`](./docs/rules/no-empty-definitions.md)                 | Disallow empty definitions                                                                        |       yes       |
 | [`no-empty-images`](./docs/rules/no-empty-images.md)                           | Disallow empty images                                                                             |       yes       |
 | [`no-empty-links`](./docs/rules/no-empty-links.md)                             | Disallow empty links                                                                              |       yes       |

docs/rules/no-emphasis-as-heading.md

@@ -0,0 +1,79 @@
+# no-emphasis-as-heading
+
+TODO
+
+## Rule Details
+
+This rule disallows using fully bolded paragraphs as headings. The use of fully bolded paragraphs as headings is a common anti-pattern that reduces document semantics and accessibility. Instead, proper heading elements (`#`, `##`, etc.) should be used.
+
+### Why This Is Important
+
+Using proper headings instead of bolded paragraphs:
+
+- Improves document structure and semantics
+- Enhances accessibility for screen readers
+- Creates proper document outline
+- Makes navigation of the document easier
+
+### What This Rule Checks
+
+This rule identifies paragraphs that:
+
+- Consist entirely of a bold element (`**text**` or `__text__`)
+- Are contained on a single line
+- Are not within list items
+- Have bold markup that spans the entire paragraph content
+
+## Examples
+
+### :x: Incorrect
+
+Examples of **incorrect** code for this rule:
+
+```md /**First Chapter**/ /__Second Chapter__/
+<!-- eslint md/no-bold-paragraph: "error" -->
+
+# Book
+
+**First Chapter**
+
+Content of the first chapter
+
+__Second Chapter__
+
+Content of the second chapter
+```
+
+### :white_check_mark: Correct
+
+Examples of **correct** code for this rule:
+
+```md
+<!-- eslint md/no-bold-paragraph: "error" -->
+
+# Book
+
+## First Chapter
+
+Content of the first chapter
+
+## Second Chapter
+
+Content of the second chapter
+
+---
+
+**Bold text** with normal text in the paragraph.
+
+Text with **bold parts** is fine.
+
+- **Bold text in a list item** is allowed.
+```
+
+## Options
+
+No options are available for this rule.
+
+## Prior Art
+
+- [textlint-rule-no-bold-paragraph](https://github.com/aborazmeh/textlint-rule-no-bold-paragraph)

src/rules/no-emphasis-as-heading.js

@@ -0,0 +1,67 @@
+/**
+ * @fileoverview Rule to disallow using fully bolded paragraphs as headings.
+ * @author lumir(lumirlumir)
+ */
+
+// @ts-nocheck -- TODO
+
+//-----------------------------------------------------------------------------
+// Type Definitions
+//-----------------------------------------------------------------------------
+
+/**
+ * @import { MarkdownRuleDefinition } from "../types.js";
+ * @typedef {"no-emphasis-as-heading"} NoEmphasisAsHeadingMessageIds
+ * @typedef {[]} NoEmphasisAsHeadingOptions
+ * @typedef {MarkdownRuleDefinition<{ RuleOptions: NoEmphasisAsHeadingOptions, MessageIds: NoEmphasisAsHeadingMessageIds }>} NoEmphasisAsHeadingRuleDefinition
+ */
+
+// --------------------------------------------------------------------------------
+// Rule Definition
+// --------------------------------------------------------------------------------
+
+export default /** @satisfies {NoEmphasisAsHeadingRuleDefinition} */ ({
+	meta: {
+		type: "problem",
+
+		docs: {
+			recommended: true,
+			description: "Disallow using fully bolded paragraphs as headings",
+			url: "https://github.com/eslint/markdown/blob/main/docs/rules/no-emphasis-as-heading.md",
+		},
+
+		messages: {
+			noEmphasisAsHeading:
+				"Fully bolded paragraphs should not be used as headings. Please use a heading instead.",
+		},
+
+		// language: "markdown",
+
+		// dialects: ["commonmark", "gfm"],
+	},
+
+	create(context) {
+		return {
+			strong(node) {
+				const parentNode = context.sourceCode.getParent(node);
+				const ancestorNode = context.sourceCode.getParent(parentNode);
+
+				if (
+					parentNode.type === "paragraph" &&
+					ancestorNode.type !== "listItem" &&
+					parentNode.position.start.line ===
+						parentNode.position.end.line && // Should be a single line.
+					parentNode.position.start.offset ===
+						node.position.start.offset && // Should have the same start offset.
+					parentNode.position.end.offset === node.position.end.offset // Should have the same end offset.
+				) {
+					context.report({
+						node,
+
+						messageId: "noEmphasisAsHeading",
+					});
+				}
+			},
+		};
+	},
+});

tests/rules/no-emphasis-as-heading.test.js

@@ -0,0 +1,115 @@
+/**
+ * @fileoverview Test for `no-emphasis-as-heading.ts`.
+ * @author lumir(lumirlumir)
+ */
+
+//------------------------------------------------------------------------------
+// Imports
+//------------------------------------------------------------------------------
+
+import rule from "../../src/rules/no-emphasis-as-heading.js";
+import markdown from "../../src/index.js";
+import { RuleTester } from "eslint";
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({
+	plugins: {
+		markdown,
+	},
+	language: "markdown/commonmark",
+});
+
+ruleTester.run("no-emphasis-as-heading", rule, {
+	valid: [
+		// Basic
+		{
+			name: "Empty",
+			code: "",
+		},
+		{
+			name: "Empty string",
+			code: "  ",
+		},
+		{
+			name: "Paragraph without bolded text",
+			code: "#Book\n\nFirst Chapter\n\nContent\n\nSecond Chapter\n\nContent",
+		},
+		{
+			name: "Paragraph with bolded text and other text",
+			code: "**Hello** World.\n\nHello **World**.",
+		},
+		{
+			name: "Paragraph with bolded text and other multiline text",
+			code: "**Hello**\nWorld.\n\nHello\n**World**.",
+		},
+		{
+			name: "Bold with whitespace inside",
+			code: "** Not fully bolded paragraph **",
+		},
+		{
+			name: "Multiple bold elements comprising entire paragraph",
+			code: "**First part** **second part**",
+		},
+
+		// ListItem
+		{
+			name: "Bold text in list item",
+			code: "- **List item**\n- __List item__",
+		},
+	],
+
+	invalid: [
+		// Basic
+		{
+			name: "Paragraph with fully bolded text",
+			code: "#Book\n\n**First Chapter**\n\nContent\n\n__Second Chapter__\n\nContent",
+			errors: [
+				{
+					messageId: "noEmphasisAsHeading",
+					line: 3,
+					column: 1,
+					endLine: 3,
+					endColumn: 18,
+				},
+				{
+					messageId: "noEmphasisAsHeading",
+					line: 7,
+					column: 1,
+					endLine: 7,
+					endColumn: 19,
+				},
+			],
+		},
+		{
+			name: "Paragraph with fully bolded single character",
+			code: "**X**",
+			errors: [
+				{
+					messageId: "noEmphasisAsHeading",
+					line: 1,
+					column: 1,
+					endLine: 1,
+					endColumn: 6,
+				},
+			],
+		},
+
+		// Blockquote
+		{
+			name: "Bold text in blockquote",
+			code: "> **Blockquote**",
+			errors: [
+				{
+					messageId: "noEmphasisAsHeading",
+					line: 1,
+					column: 3,
+					endLine: 1,
+					endColumn: 17,
+				},
+			],
+		},
+	],
+});