Add MD022 with tests, create shared module.

lib/markdownlint.js

@@ -3,6 +3,7 @@
 var fs = require("fs");
 var md = require("markdown-it")();
 var rules = require("./rules");
+var shared = require("./shared");
 
 function numberComparison(a, b) {
   return a - b;
@@ -18,7 +19,7 @@ function lintFile(file, config, callback) {
       callback(err);
     } else {
       var tokens = md.parse(contents, {});
-      var lines = contents.split(/\r\n|\r|\n/);
+      var lines = contents.split(shared.newLineRe);
       tokens.forEach(function forToken(token) {
         if (token.lines) {
           token.line = lines[token.lines[0]];

lib/rules.js

@@ -1,5 +1,7 @@
 "use strict";
 
+var shared = require("./shared");
+
 function indentFor(token) {
   return token.line.length - token.line.trimLeft().length;
 }
@@ -253,7 +255,7 @@ module.exports = [
       filterTokens(params.tokens, "code_block", "fence")
         .forEach(function forToken(token) {
           if (token.content && token.content
-            .split(/\r\n|\r|\n/)
+            .split(shared.newLineRe)
             .filter(function filterLine(line) {
               return line;
             }).every(function forLine(line) {
@@ -318,6 +320,42 @@ module.exports = [
     }
   },
 
+  {
+    "name": "MD022",
+    "desc": "Headers should be surrounded by blank lines",
+    "func": function MD022(params, errors) {
+      var prevHeadingLineNumber = 0;
+      var prevMaxLineIndex = -1;
+      var needBlankLine = false;
+      params.tokens.forEach(function forToken(token) {
+        if (token.type === "heading_open") {
+          if ((token.lines[0] - prevMaxLineIndex) === 0) {
+            errors.push(token.lineNumber);
+          }
+          prevHeadingLineNumber = token.lineNumber;
+        } else if (token.type === "heading_close") {
+          needBlankLine = true;
+        } else if (token.type === "inline") {
+          token.content.split(shared.newLineRe)
+            .forEach(function forLine(line, offset) {
+              if (/^(-+|=+)\s*$/.test(line)) {
+                errors.push(token.lines[0] + offset);
+              }
+            });
+        }
+        if (token.lines) {
+          if (needBlankLine) {
+            if ((token.lines[0] - prevMaxLineIndex) === 0) {
+              errors.push(prevHeadingLineNumber);
+            }
+            needBlankLine = false;
+          }
+          prevMaxLineIndex = Math.max(prevMaxLineIndex, token.lines[1]);
+        }
+      });
+    }
+  },
+
   {
     "name": "MD028",
     "desc": "Blank line inside blockquote",

lib/shared.js

@@ -0,0 +1,3 @@
+"use strict";
+
+module.exports.newLineRe = /\r\n|\r|\n/;