Fix(nodejs/event_dispatcher): update error/resp handlers (#123)

- (nodejs) Prevent crash when `http`/`https` emits an error by adding an 'error' listener
- (nodejs) Fix `requestCallback` to conform to its role as a 'response' listener; notably, ensure it is called when the first argument is interpeted as the `http.IncomingMessage`, and _not_ called in the event of an error (as expected by `Optimizely#_sendImpressionEvent`/`Optimizely#track`).

Tested that this version (as 2.1.2-0) _does_ emit the messages expected in the demo app.

Fixes #122 
Fixes #124

Author: Tyler Brandt

packages/optimizely-sdk/lib/plugins/event_dispatcher/index.node.js

@@ -30,7 +30,6 @@ module.exports = {
   dispatchEvent: function(eventObj, callback) {
     // Non-POST requests not supported
     if (eventObj.httpVerb !== 'POST') {
-      callback(new Error('httpVerb not supported: ' + eventObj.httpVerb));
       return;
     }
 
@@ -52,13 +51,15 @@ module.exports = {
       }
     };
 
-    var requestCallback = function(error, response, body) {
-      if (response && response.statusCode && response.statusCode >= 200 && response.statusCode < 400 && callback && typeof callback === 'function') {
-        callback();
+    var requestCallback = function(response) {
+      if (response && response.statusCode && response.statusCode >= 200 && response.statusCode < 400) {
+        callback(response);
       }
     };
 
     var req = (parsedUrl.protocol === 'http:' ? http : https).request(requestOptions, requestCallback);
+    // Add no-op error listener to prevent this from throwing
+    req.on('error', function() {});
     req.write(dataString);
     req.end();
     return req;

packages/optimizely-sdk/lib/plugins/event_dispatcher/index.node.tests.js

@@ -49,13 +49,9 @@ describe('lib/plugins/event_dispatcher/node', function() {
           httpVerb: 'POST',
         };
 
-        eventDispatcher.dispatchEvent(eventObj)
-        .on('response', function(response) {
-          assert.isTrue(response.statusCode === 200);
+        eventDispatcher.dispatchEvent(eventObj, function(resp) {
+          assert.equal(200, resp.statusCode);
           done();
-        })
-        .on('error', function(error) {
-          assert.fail('status code okay', 'status code not okay', '');
         });
       });
 
@@ -70,15 +66,15 @@ describe('lib/plugins/event_dispatcher/node', function() {
 
         eventDispatcher.dispatchEvent(eventObj, stubCallback.callback)
         .on('response', function(response) {
-          done();
           sinon.assert.calledOnce(stubCallback.callback);
+          done();
         })
         .on('error', function(error) {
           assert.fail('status code okay', 'status code not okay', '');
         });
       });
 
-      it('rejects GET httpVerb', function(done) {
+      it('rejects GET httpVerb', function() {
         var eventObj = {
           url: 'https://cdn.com/event',
           params: {
@@ -87,16 +83,22 @@ describe('lib/plugins/event_dispatcher/node', function() {
           httpVerb: 'GET',
         };
 
-        var callback = function(err) {
-          if (err) {
-            done();
-          } else {
-            done(new Error('expected error not thrown'));
-          }
-        };
-
+        var callback = sinon.spy();
         eventDispatcher.dispatchEvent(eventObj, callback);
+        sinon.assert.notCalled(callback);
       });
     });
+
+    it('does not throw in the event of an error', function() {
+      var eventObj = {
+        url: 'https://example',
+        params: {},
+        httpVerb: 'POST',
+      };
+
+      var callback = sinon.spy();
+      eventDispatcher.dispatchEvent(eventObj, callback);
+      sinon.assert.notCalled(callback);
+    });
   });
 });