Adding checks for mixing SubscribeAsync and SubscribePresenceAsync

Author: Collin Dauphinee

PusherClient.Tests/AcceptanceTests/PresenceChannel.cs

@@ -94,7 +94,7 @@ public void PresenceChannelShouldAddAMemberWhenGivenAMemberAsync()
         }
 
         [Test]
-        public void PresenceChannelShouldUseGenericWhenGivenAMemberAsync()
+        public void PresenceChannelShouldAddATypedMemberWhenGivenAMemberAsync()
         {
             // Arrange
             var stubOptions = new PusherOptions

PusherClient.Tests/UnitTests/PusherTests.cs

@@ -194,5 +194,29 @@ public void PusherShouldThrowAnExceptionWhenSubscribePresenceIsCalledWithADiffer
             Assert.IsNotNull(caughtException);
             StringAssert.Contains("Cannot change channel member type; was previously defined as", caughtException.Message);
         }
+
+        [Test]
+        public void PusherShouldThrowAnExceptionWhenSubscribePresenceIsCalledAfterSubscribe()
+        {
+            // Arrange
+            InvalidOperationException caughtException = null;
+
+            // Act
+            var pusher = new Pusher("FakeAppKey", new PusherOptions { Authorizer = new FakeAuthoriser("test") });
+            AsyncContext.Run(() => pusher.SubscribeAsync("presence-123"));
+
+            try
+            {
+                AsyncContext.Run(() => pusher.SubscribePresenceAsync<int>("presence-123"));
+            }
+            catch (InvalidOperationException ex)
+            {
+                caughtException = ex;
+            }
+
+            // Assert
+            Assert.IsNotNull(caughtException);
+            StringAssert.Contains("This presence channel has already been created without specifying the member info type", caughtException.Message);
+        }
     }
 }

PusherClient/Pusher.cs

@@ -269,6 +269,7 @@ public async Task<GenericPresenceChannel<MemberT>> SubscribePresenceAsync<Member
             if (channelType != ChannelTypes.Presence)
                 throw new ArgumentException("The channel name must be refer to a presence channel", nameof(channelName));
 
+            // We need to keep track of the type we want the channel to be, in case it gets created or re-created later.
             _presenceChannelFactories.AddOrUpdate(channelName, 
                 (_) => Tuple.Create<Type, Func<Channel>>(typeof(MemberT), 
                     () => new GenericPresenceChannel<MemberT>(channelName, this)), 
@@ -279,8 +280,18 @@ public async Task<GenericPresenceChannel<MemberT>> SubscribePresenceAsync<Member
                     return existing;
                 });
 
-            var result = await SubscribeAsync(channelName);
-            return result as GenericPresenceChannel<MemberT>;
+            var channel = await SubscribeAsync(channelName);
+
+            var result = channel as GenericPresenceChannel<MemberT>;
+            if (result == null)
+            {
+                if (channel is PresenceChannel)
+                    throw new InvalidOperationException("This presence channel has already been created without specifying the member info type");
+                else
+                    throw new InvalidOperationException($"The presence channel found is an unexpected type: {channel.GetType().Name}");
+            }
+
+            return result;
         }
 
         private async Task<Channel> SubscribeToChannel(string channelName)