Format results via toString, add test to verify.

.eslintrc

@@ -126,7 +126,7 @@
         "key-spacing": [2, { "beforeColon": false, "afterColon": true }],
         "max-depth": [2, 4],
         "max-len": [2, 80, 2],
-        "max-nested-callbacks": [2, 2],
+        "max-nested-callbacks": [2, 3],
         "max-params": [2, 4],
         "max-statements": [0, 10],
         "new-cap": 2,

lib/markdownlint.js

@@ -5,6 +5,30 @@ var md = require("markdown-it")();
 var rules = require("./rules");
 var shared = require("./shared");
 
+var ruleToDescription = {};
+rules.forEach(function forRule(rule) {
+  ruleToDescription[rule.name] = rule.desc;
+});
+
+function Results() { }
+Results.prototype.toString = function resultsToString() {
+  var self = this;
+  var results = [];
+  Object.keys(self).forEach(function forFile(file) {
+    var fileResults = self[file];
+    Object.keys(fileResults).forEach(function forRule(rule) {
+      var ruleResults = fileResults[rule];
+      ruleResults.forEach(function forLine(lineNumber) {
+        var result =
+          file + ": " + lineNumber + ": " +
+          rule + " " + ruleToDescription[rule];
+        results.push(result);
+      });
+    });
+  });
+  return results.join("\n");
+};
+
 function numberComparison(a, b) {
   return a - b;
 }
@@ -55,7 +79,7 @@ module.exports = function markdownlint(options, callback) {
   callback = callback || function noop() {};
   var files = options.files || [];
   var config = options.config || { "default": true };
-  var results = {};
+  var results = new Results();
   function lintFiles() {
     var file = files.shift();
     if (file) {

test/markdownlint-test.js

@@ -80,6 +80,44 @@ module.exports.projectFiles = function projectFiles(test) {
   });
 };
 
+module.exports.resultFormatting = function resultFormatting(test) {
+  test.expect(3);
+  var options = {
+    "files": [
+      "./test/atx_header_spacing.md",
+      "./test/first_header_bad_atx.md"
+    ]
+  };
+  markdownlint(options, function callback(err, actualResult) {
+    test.ifError(err);
+    var expectedResult = {
+      "./test/atx_header_spacing.md": {
+        "MD002": [ 3 ],
+        "MD018": [ 1 ],
+        "MD019": [ 3, 5 ]
+      },
+      "./test/first_header_bad_atx.md": {
+        "MD002": [ 1 ]
+      }
+    };
+    test.deepEqual(actualResult, expectedResult, "Undetected issues.");
+    var actualMessage = actualResult.toString();
+    var expectedMessage =
+      "./test/atx_header_spacing.md: 3: MD002" +
+      " First header should be a h1 header\n" +
+      "./test/atx_header_spacing.md: 1: MD018" +
+      " No space after hash on atx style header\n" +
+      "./test/atx_header_spacing.md: 3: MD019" +
+      " Multiple spaces after hash on atx style header\n" +
+      "./test/atx_header_spacing.md: 5: MD019" +
+      " Multiple spaces after hash on atx style header\n" +
+      "./test/first_header_bad_atx.md: 1: MD002" +
+      " First header should be a h1 header";
+    test.equal(actualMessage, expectedMessage, "Incorrect message.");
+    test.done();
+  });
+};
+
 module.exports.missingOptions = function missingOptions(test) {
   test.expect(2);
   markdownlint(null, function callback(err, result) {