fix(change-stream): fix change stream resuming with promises

If a change stream resume occurred, and the user was using the
Promise-based version of .next, the promise would resolve before
waiting for the change stream to resume, resulting in bad behavior.

Fixes NODE-1493

Author: daprahamian

lib/change_stream.js

@@ -129,6 +129,13 @@ var createChangeStreamCursor = function(self) {
     self.emit('error', error);
   });
 
+  if (self.pipeDestinations) {
+    const cursorStream = changeStreamCursor.stream(self.streamOptions);
+    for (let pipeDestination in self.pipeDestinations) {
+      cursorStream.pipe(pipeDestination);
+    }
+  }
+
   return changeStreamCursor;
 };
 
@@ -303,27 +310,22 @@ var processNewChange = function(self, err, change, callback) {
     // Handle resumable MongoNetworkErrors
     if (isResumableError(err) && !self.attemptingResume) {
       self.attemptingResume = true;
-      return self.cursor.close(function(closeErr) {
-        if (closeErr) {
-          if (callback) return callback(err, null);
-          return self.promiseLibrary.reject(err);
-        }
-
-        // Establish a new cursor
-        self.cursor = createChangeStreamCursor(self);
-
-        // Attempt to reconfigure piping
-        if (self.pipeDestinations) {
-          var cursorStream = self.cursor.stream(self.streamOptions);
-          for (var pipeDestination in self.pipeDestinations) {
-            cursorStream.pipe(pipeDestination);
+      if (callback) {
+        return self.cursor.close(function(closeErr) {
+          if (closeErr) {
+            return callback(err, null);
           }
-        }
 
-        // Attempt the next() operation again
-        if (callback) return self.next(callback);
-        return self.next();
-      });
+          self.cursor = createChangeStreamCursor(self);
+
+          return self.next(callback);
+        });
+      }
+
+      return self.cursor
+        .close()
+        .then(() => (self.cursor = createChangeStreamCursor(self)))
+        .then(() => self.next());
     }
 
     if (typeof callback === 'function') return callback(err, null);