support the nosideeffects tag (Closure Compiler only) (#605)

lib/jsdoc/tag/dictionary/definitions.js

@@ -931,6 +931,12 @@ exports.closureTags = {
         onTagged: ignore
     },
     // Closure Compiler only
+    nosideeffects: {
+        onTagged: function(doclet) {
+            doclet.modifies = [];
+        }
+    },
+    // Closure Compiler only
     override: {
         mustNotHaveValue: true,
         onTagged: function(doclet) {

test/fixtures/nosideeffectstag.js

@@ -0,0 +1,5 @@
+/**
+ * A function that does nothing.
+ * @nosideeffects
+ */
+function doNothing() {}

test/specs/tags/nosideeffectstag.js

@@ -0,0 +1,21 @@
+'use strict';
+
+describe('@nosideeffects tag', function() {
+    afterEach(function() {
+        jasmine.restoreTagDictionary();
+    });
+
+    describe('Closure Compiler tags', function() {
+        beforeEach(function() {
+            jasmine.replaceTagDictionary('closure');
+        });
+
+        it('should set the doclet\'s `modifies` property to an empty array', function() {
+            var docSet = jasmine.getDocSetFromFile('test/fixtures/nosideeffectstag.js');
+            var doNothing = docSet.getByLongname('doNothing')[0];
+
+            expect(Array.isArray(doNothing.modifies)).toBe(true);
+            expect(doNothing.modifies.length).toBe(0);
+        });
+    });
+});