Prevent race condition in TFClient (RobotWebTools#489)

If a TFClient is disposed while a service call to update the goal is ongoing it will subscribe to the republished topic even if none is listening.

src/tf/TFClient.ts

@@ -52,6 +52,7 @@ function TFClient(options) {
   this.frameInfos = {};
   this.republisherUpdateRequested = false;
   this._subscribeCB = null;
+  this._isDisposed = false;
 
   // Create an Action client
   this.actionClient = new ActionClient({
@@ -143,6 +144,12 @@ TFClient.prototype.updateGoal = function () {
  * @param response the service response containing the topic name
  */
 TFClient.prototype.processResponse = function (response) {
+  // Do not setup a topic subscription if already disposed. Prevents a race condition where
+  // The dispose() function is called before the service call receives a response.
+  if (this._isDisposed) {
+    return;
+  }
+
   // if we subscribed to a topic before, unsubscribe so
   // the republisher stops publishing it
   if (this.currentTopic) {

test/tfclient.test.js

@@ -0,0 +1,30 @@
+var expect = require('chai').expect;
+var ROSLIB = require('..');
+
+describe('TFClient', function() {
+
+  describe('dispose', function() {
+
+    it('should not subscribe to republished topic if already disposed', function() {
+      // This test makes sure we do not subscribe to the republished topic if the 
+      // tf client has already been disposed when we get the response (from the setup request)
+      // from the server.
+
+      var dummyROS = {
+        idCounter: 0,
+        on: () => {},
+        off: () => {},
+        callOnConnection: () => {}
+      }
+
+      var tfclient = new ROSLIB.TFClient({ros: dummyROS});
+      tfclient.dispose();
+
+      // Simulated a response from the server after the client is already disposed
+      tfclient.processResponse({topic_name: "/repub_1"});
+
+      expect(tfclient.currentTopic).to.be.false;
+    });
+  });
+
+});