Add new rule no-heading-like-paragraph

Closes GH-107.

doc/rules.md

@@ -2,7 +2,7 @@
 
 # List of Rules
 
-This document describes all (59)
+This document describes all (60)
 available rules, what they check for, examples of
 what they warn for, and how to fix their warnings.
 
@@ -103,6 +103,7 @@ For example, as follows:
 -   [no-file-name-outer-dashes](#no-file-name-outer-dashes)
 -   [no-heading-content-indent](#no-heading-content-indent)
 -   [no-heading-indent](#no-heading-indent)
+-   [no-heading-like-paragraph](#no-heading-like-paragraph)
 -   [no-heading-punctuation](#no-heading-punctuation)
 -   [no-html](#no-html)
 -   [no-inline-padding](#no-inline-padding)
@@ -1738,6 +1739,32 @@ When this rule is turned on, the following file
 10:4: Remove 3 spaces before this heading
 ```
 
+## `no-heading-like-paragraph`
+
+Warn for h7+ “headings”.
+
+When this rule is turned on, the following file
+`valid.md` is ok:
+
+```markdown
+###### Alpha
+
+Bravo.
+```
+
+When this rule is turned on, the following file
+`invalid.md` is **not** ok:
+
+```markdown
+####### Charlie
+
+Delta.
+```
+
+```text
+1:1-1:16: This looks like a heading but has too many hashes
+```
+
 ## `no-heading-punctuation`
 
 Warn when a heading ends with a a group of characters.

packages/remark-lint/lib/rules.js

@@ -38,6 +38,7 @@ module.exports = {
   'no-file-name-outer-dashes': require('./rules/no-file-name-outer-dashes.js'),
   'no-heading-content-indent': require('./rules/no-heading-content-indent.js'),
   'no-heading-indent': require('./rules/no-heading-indent.js'),
+  'no-heading-like-paragraph': require('./rules/no-heading-like-paragraph.js'),
   'no-heading-punctuation': require('./rules/no-heading-punctuation.js'),
   'no-html': require('./rules/no-html.js'),
   'no-inline-padding': require('./rules/no-inline-padding.js'),

packages/remark-lint/lib/rules/no-heading-like-paragraph.js

@@ -0,0 +1,50 @@
+/**
+ * @author Titus Wormer
+ * @copyright 2015 Titus Wormer
+ * @license MIT
+ * @module no-heading-like-paragraph
+ * @fileoverview
+ *   Warn for h7+ “headings”.
+ *
+ * @example {"name": "valid.md"}
+ *
+ *   ###### Alpha
+ *
+ *   Bravo.
+ *
+ * @example {"name": "invalid.md", "label": "input"}
+ *
+ *   ####### Charlie
+ *
+ *   Delta.
+ *
+ * @example {"name": "invalid.md", "label": "output"}
+ *
+ *   1:1-1:16: This looks like a heading but has too many hashes
+ */
+
+'use strict';
+
+var visit = require('unist-util-visit');
+var generated = require('unist-util-generated');
+
+module.exports = noHeadingLikeParagraph;
+
+var fence = '#######';
+
+function noHeadingLikeParagraph(tree, file) {
+  visit(tree, 'paragraph', visitor);
+
+  function visitor(node) {
+    var head = node.children[0];
+
+    if (
+      head &&
+      head.type === 'text' &&
+      head.value.slice(0, fence.length) === fence &&
+      !generated(node)
+    ) {
+      file.message('This looks like a heading but has too many hashes', node);
+    }
+  }
+}