requireHyphenBeforeDescription: improve multiline support checks

Fixes jscs-dev/node-jscs#1579

Author: Alexej Yaroshevich

lib/rules/validate-jsdoc/require-hyphen-before-description.js

@@ -17,6 +17,12 @@ function requireHyphenBeforeDescription(node, tag, err) {
         return;
     }
 
+    // skip reporting if there is new line in description
+    // todo: check this with newline of name and description when it'll be possible
+    if (tag.value.indexOf('\n') !== -1 && tag.description.indexOf('\n') === -1) {
+        return;
+    }
+
     if (tag.description.substring(0, 2) !== '- ') {
         err('Missing hyphen before description', tag.loc);
     }

test/lib/rules/validate-jsdoc/require-hyphen-before-description.js

@@ -55,7 +55,37 @@ describe('lib/rules/validate-jsdoc/require-hyphen-before-description', function
                     function yey(yay) {
                     }
                 }
-
+            }, {
+                it: 'should not report if description started with newline',
+                code: function () {
+                    /**
+                     * @param {number} yay
+                     * Description without hyphen.
+                     */
+                    function yey(yay) {
+                    }
+                }
+            }, {
+                it: 'should report if description has newline inside',
+                errors: 1,
+                code: function () {
+                    /**
+                     * @param {number} yay Started on the original line
+                     *   without hyphen should be reported.
+                     */
+                    function yey(yay) {
+                    }
+                }
+            }, {
+                it: 'should not report if description has newline inside (with hyphen)',
+                code: function () {
+                    /**
+                     * @param {number} yay - Started on the original line
+                     *   without hyphen should be reported.
+                     */
+                    function yey(yay) {
+                    }
+                }
             }
             /* jshint ignore:end */
         ]);