Add validation of onError callback object for rules.

lib/markdownlint.js

@@ -324,8 +324,36 @@ function lintContent(
     var ruleNameFriendly = rule.names[0];
     var ruleName = ruleNameFriendly.toUpperCase();
     params.config = effectiveConfig[ruleName];
+    function throwError(property) {
+      throw new Error(
+        "Property '" + property + "' of onError parameter is incorrect.");
+    }
     var errors = [];
     function onError(errorInfo) {
+      if (!errorInfo ||
+        !errorInfo.lineNumber ||
+        !shared.isNumber(errorInfo.lineNumber)) {
+        throwError("lineNumber");
+      }
+      if ((errorInfo.detail !== null) &&
+        (errorInfo.detail !== undefined) &&
+        (!shared.isString(errorInfo.detail) ||
+         shared.isEmptyString(errorInfo.detail))) {
+        throwError("detail");
+      }
+      if ((errorInfo.context !== null) &&
+        (errorInfo.context !== undefined) &&
+        (!shared.isString(errorInfo.context) ||
+         shared.isEmptyString(errorInfo.context))) {
+        throwError("context");
+      }
+      if (errorInfo.range &&
+        (!Array.isArray(errorInfo.range) ||
+         (errorInfo.range.length !== 2) ||
+         !shared.isNumber(errorInfo.range[0]) ||
+         !shared.isNumber(errorInfo.range[1]))) {
+        throwError("range");
+      }
       errors.push({
         "lineNumber": errorInfo.lineNumber + frontMatterLines.length,
         "detail": errorInfo.detail || null,

lib/shared.js

@@ -46,6 +46,11 @@ module.exports.clone = function clone(obj) {
   return assign({}, obj);
 };
 
+// Returns true iff the input is a number
+module.exports.isNumber = function isNumber(obj) {
+  return typeof obj === "number";
+};
+
 // Returns true iff the input is a string
 module.exports.isString = function isString(obj) {
   return typeof obj === "string";

test/markdownlint-test.js

@@ -2008,3 +2008,73 @@ function customRulesThrowForString(test) {
     test.done();
   });
 };
+
+module.exports.customRulesOnErrorNull = function customRulesOnErrorNull(test) {
+  test.expect(4);
+  var options = {
+    "customRules": [
+      {
+        "names": [ "name" ],
+        "description": "description",
+        "tags": [ "tag" ],
+        "function": function onErrorNull(params, onError) {
+          onError(null);
+        }
+      }
+    ],
+    "strings": [ "String" ]
+  };
+  test.throws(function badErrorCall() {
+    markdownlint.sync(options);
+  }, function testError(err) {
+    test.ok(err, "Did not get an error for null object.");
+    test.ok(err instanceof Error, "Error not instance of Error.");
+    test.equal(err.message,
+      "Property 'lineNumber' of onError parameter is incorrect.",
+      "Incorrect message for bad object.");
+    return true;
+  }, "Did not get exception for null object.");
+  test.done();
+};
+
+module.exports.customRulesOnErrorBad = function customRulesOnErrorBad(test) {
+  test.expect(52);
+  [
+    [ "lineNumber", [ null, "string" ] ],
+    [ "detail", [ 10, "", [] ] ],
+    [ "context", [ 10, "", [] ] ],
+    [ "range", [ 10, [], [ 10 ], [ 10, null ], [ 10, 11, 12 ] ] ]
+  ].forEach(function forProperty(property) {
+    var propertyName = property[0];
+    property[1].forEach(function forPropertyValue(propertyValue) {
+      var badObject = {
+        "lineNumber": 1
+      };
+      badObject[propertyName] = propertyValue;
+      var options = {
+        "customRules": [
+          {
+            "names": [ "name" ],
+            "description": "description",
+            "tags": [ "tag" ],
+            "function": function onErrorBad(params, onError) {
+              onError(badObject);
+            }
+          }
+        ],
+        "strings": [ "String" ]
+      };
+      test.throws(function badErrorCall() {
+        markdownlint.sync(options);
+      }, function testError(err) {
+        test.ok(err, "Did not get an error for bad object.");
+        test.ok(err instanceof Error, "Error not instance of Error.");
+        test.equal(err.message,
+          "Property '" + propertyName + "' of onError parameter is incorrect.",
+          "Incorrect message for bad object.");
+        return true;
+      }, "Did not get exception for bad object.");
+    });
+  });
+  test.done();
+};

test/rules/any-blockquote.js

@@ -14,8 +14,7 @@ module.exports = {
       onError({
         "lineNumber": blockquote.lineNumber,
         "detail": "Blockquote spans " + lines + " line(s).",
-        "context": blockquote.line.substr(0, 7),
-        "range": null
+        "context": blockquote.line.substr(0, 7)
       });
     });
   }

test/rules/every-n-lines.js

@@ -13,9 +13,7 @@ module.exports = {
       if ((lineNumber % n) === 0) {
         onError({
           "lineNumber": lineNumber,
-          "detail": "Line number " + lineNumber,
-          "context": null,
-          "range": null
+          "detail": "Line number " + lineNumber
         });
       }
     });

test/rules/first-line.js

@@ -9,10 +9,7 @@ module.exports = {
   "function": function rule(params, onError) {
     // Unconditionally report an error for line 1
     onError({
-      "lineNumber": 1,
-      "detail": null,
-      "context": null,
-      "range": null
+      "lineNumber": 1
     });
   }
 };

test/rules/letters-E-X.js

@@ -17,9 +17,7 @@ module.exports = {
         if (index !== -1) {
           onError({
             "lineNumber": text.lineNumber,
-            "detail": null,
-            "context": text.content.substr(index - 1, 4),
-            "range": null
+            "context": text.content.substr(index - 1, 4)
           });
         }
       });