Avoid emitting GROUP_FOCUSED event if the group has not changed

widget-controller.js triggers a reload of annotations whenever a
GROUP_FOCUSED event is emitted. Avoid reloading annotations
unnecessarily if group.focus() is called with the currently focused
group.

h/static/scripts/groups.js

@@ -25,7 +25,7 @@ function groups(localStorage, session, settings, $rootScope, $http) {
 
   function all() {
     return session.state.groups || [];
-  };
+  }
 
   // Return the full object for the group with the given id.
   function get(id) {
@@ -35,7 +35,7 @@ function groups(localStorage, session, settings, $rootScope, $http) {
         return gs[i];
       }
     }
-  };
+  }
 
   /** Leave the group with the given ID.
    * Returns a promise which resolves when the action completes.
@@ -51,7 +51,7 @@ function groups(localStorage, session, settings, $rootScope, $http) {
     // by optimistically updating the session state
 
     return response;
-  };
+  }
 
 
   /** Return the currently focused group. If no group is explicitly focused we
@@ -72,12 +72,15 @@ function groups(localStorage, session, settings, $rootScope, $http) {
 
   /** Set the group with the passed id as the currently focused group. */
   function focus(id) {
-   var g = get(id);
-   if (g) {
-     focusedGroup = g;
-     localStorage.setItem(STORAGE_KEY, g.id);
-     $rootScope.$broadcast(events.GROUP_FOCUSED, g.id);
-   }
+    var prevFocused = focused();
+    var g = get(id);
+    if (g) {
+      focusedGroup = g;
+      localStorage.setItem(STORAGE_KEY, g.id);
+      if (prevFocused.id !== g.id) {
+        $rootScope.$broadcast(events.GROUP_FOCUSED, g.id);
+      }
+    }
   }
 
   // reset the focused group if the user leaves it

h/static/scripts/test/groups-test.js

@@ -45,7 +45,7 @@ describe('groups', function() {
         }
       }
     };
-    fakeHttp = sandbox.stub()
+    fakeHttp = sandbox.stub();
   });
 
   afterEach(function () {
@@ -134,7 +134,7 @@ describe('groups', function() {
     });
   });
 
-  describe('.focus() method', function() {
+  describe('.focus()', function() {
     it('sets the focused group to the named group', function() {
       var s = service();
       s.focus('id2');
@@ -155,6 +155,20 @@ describe('groups', function() {
 
       assert.calledWithMatch(fakeLocalStorage.setItem, sinon.match.any, 'id3');
     });
+
+    it('emits the GROUP_FOCUSED event if the focused group changed', function () {
+      var s = service();
+      s.focus('id3');
+      assert.calledWith(fakeRootScope.$broadcast, events.GROUP_FOCUSED, 'id3');
+    });
+
+    it('does not emit GROUP_FOCUSED if the focused group did not change', function () {
+      var s = service();
+      s.focus('id3');
+      fakeRootScope.$broadcast = sinon.stub();
+      s.focus('id3');
+      assert.notCalled(fakeRootScope.$broadcast);
+    });
   });
 
   describe('.leave()', function () {