Add MD036 with tests.

README.md

@@ -66,6 +66,7 @@ cases come directly from that project.
 * **MD033** - Inline HTML
 * **MD034** - Bare URL used
 * **MD035** - Horizontal rule style
+* **MD036** - Emphasis used instead of a header
 
 See [Rules.md](doc/Rules.md) for more details.
 
@@ -77,9 +78,10 @@ See [Rules.md](doc/Rules.md) for more details.
 * **blockquote** - MD027, MD028
 * **bullet** - MD004, MD005, MD006, MD007, MD032
 * **code** - MD014, MD031
+* **emphasis** - MD036
 * **hard_tab** - MD010
 * **headers** - MD001, MD002, MD003, MD018, MD019, MD020, MD021, MD022, MD023,
-  MD024, MD025, MD026
+  MD024, MD025, MD026, MD036
 * **hr** - MD035
 * **html** - MD033
 * **indentation** - MD005, MD006, MD007, MD027

doc/Rules.md

@@ -765,3 +765,32 @@ rules are different than the first one encountered in the document. If you
 want to configure the rule to match a specific style, the parameter given to
 the 'style' option is a string containing the exact horizontal rule text that
 is allowed.
+
+## MD036 - Emphasis used instead of a header
+
+Tags: headers, emphasis
+
+This check looks for instances where emphasized (i.e. bold or italic) text is
+used to separate sections, where a header should be used instead:
+
+    **My document**
+
+    Lorem ipsum dolor sit amet...
+
+    _Another section_
+
+    Consectetur adipiscing elit, sed do eiusmod.
+
+To fix this, use markdown headers instead of emphasized text to denote
+sections:
+
+    # My document
+
+    Lorem ipsum dolor sit amet...
+
+    ## Another section
+
+    Consectetur adipiscing elit, sed do eiusmod.
+
+Note: this rule looks for paragraphs that consist entirely of emphasized text.
+It won't fire on emphasis used within regular text.

lib/rules.js

@@ -667,5 +667,38 @@ module.exports = [
         }
       });
     }
+  },
+
+  {
+    "name": "MD036",
+    "desc": "Emphasis used instead of a header",
+    "tags": [ "headers", "emphasis" ],
+    "func": function MD036(params, errors) {
+      var lineNumber = 0;
+      function base(token) {
+        lineNumber = token.lineNumber;
+        if (token.type === "paragraph_open") {
+          return function inParagraph(t) {
+            if ((t.type === "inline") &&
+                (t.children.length === 3) &&
+                ((t.children[0].type === "strong_open") ||
+                 (t.children[0].type === "em_open")) &&
+                (t.children[1].type === "text")) {
+              errors.push(lineNumber);
+            }
+          };
+        } else if (token.type === "blockquote_open") {
+          return function inBlockquote(t) {
+            if (t.type !== "blockquote_close") {
+              return inBlockquote;
+            }
+          };
+        }
+      }
+      var state = base;
+      params.tokens.forEach(function forToken(token) {
+        state = state(token) || base;
+      });
+    }
   }
 ];

test/emphasis_instead_of_headers.md

@@ -0,0 +1,35 @@
+**Section 1: the first section {MD036}**
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
+incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis
+nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore
+eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt
+in culpa qui officia deserunt mollit anim id est laborum.
+
+__Section 1.1: another section {MD036}__
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
+incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis
+nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore
+eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt
+in culpa qui officia deserunt mollit anim id est laborum.
+
+*Section 2: yet more sections {MD036}*
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
+incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis
+nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore
+eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt
+in culpa qui officia deserunt mollit anim id est laborum.
+
+_Section 3: oh no more sections {MD036}_
+
+This is a normal paragraph
+**that just happens to have emphasized text in**
+even though the emphasized text is on its own line.
+
+This is another **normal** paragraph with some text in it. This also should
+not trigger the rule.

test/markdownlint-test.js

@@ -498,7 +498,7 @@ module.exports.badFileSync = function badFileSync(test) {
 };
 
 module.exports.readme = function readme(test) {
-  test.expect(83);
+  test.expect(86);
   var tagToRules = {};
   rules.forEach(function forRule(rule) {
     rule.tags.forEach(function forTag(tag) {
@@ -555,7 +555,7 @@ module.exports.readme = function readme(test) {
 };
 
 module.exports.doc = function doc(test) {
-  test.expect(127);
+  test.expect(131);
   fs.readFile("doc/Rules.md", shared.utf8Encoding,
     function readFile(err, contents) {
       test.ifError(err);