[Feature] Allow switching voice channels without disconnecting (external clients only) (#2866)

* eh well it should work

* fix issues

* make sure an external client is used

src/Discord.Net.Core/Entities/Channels/IAudioChannel.cs

@@ -23,11 +23,12 @@ namespace Discord
         /// <param name="selfDeaf">Determines whether the client should deaf itself upon connection.</param>
         /// <param name="selfMute">Determines whether the client should mute itself upon connection.</param>
         /// <param name="external">Determines whether the audio client is an external one or not.</param>
+        /// <param name="disconnect">Determines whether the client should send a disconnect call before sending the new voice state.</param>
         /// <returns>
         ///     A task representing the asynchronous connection operation. The task result contains the
         ///     <see cref="IAudioClient"/> responsible for the connection.
         /// </returns>
-        Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false);
+        Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false, bool disconnect = true);
 
         /// <summary>
         ///     Disconnects from this audio channel.

src/Discord.Net.Rest/Entities/Channels/RestGroupChannel.cs

@@ -261,7 +261,7 @@ namespace Discord.Rest
         #region IAudioChannel
         /// <inheritdoc />
         /// <exception cref="NotSupportedException">Connecting to a group channel is not supported.</exception>
-        Task<IAudioClient> IAudioChannel.ConnectAsync(bool selfDeaf, bool selfMute, bool external) { throw new NotSupportedException(); }
+        Task<IAudioClient> IAudioChannel.ConnectAsync(bool selfDeaf, bool selfMute, bool external, bool disconnect) { throw new NotSupportedException(); }
         Task IAudioChannel.DisconnectAsync() { throw new NotSupportedException(); }
         Task IAudioChannel.ModifyAsync(Action<AudioChannelProperties> func, RequestOptions options) { throw new NotSupportedException(); }
         #endregion

src/Discord.Net.Rest/Entities/Channels/RestVoiceChannel.cs

@@ -89,7 +89,7 @@ namespace Discord.Rest
         #region IAudioChannel
         /// <inheritdoc />
         /// <exception cref="NotSupportedException">Connecting to a REST-based channel is not supported.</exception>
-        Task<IAudioClient> IAudioChannel.ConnectAsync(bool selfDeaf, bool selfMute, bool external) { throw new NotSupportedException(); }
+        Task<IAudioClient> IAudioChannel.ConnectAsync(bool selfDeaf, bool selfMute, bool external, bool disconnect) { throw new NotSupportedException(); }
         Task IAudioChannel.DisconnectAsync() { throw new NotSupportedException(); }
         Task IAudioChannel.ModifyAsync(Action<AudioChannelProperties> func, RequestOptions options) { throw new NotSupportedException(); }
         #endregion

src/Discord.Net.WebSocket/Entities/Channels/SocketGroupChannel.cs

@@ -387,7 +387,7 @@ namespace Discord.WebSocket
         #region IAudioChannel
         /// <inheritdoc />
         /// <exception cref="NotSupportedException">Connecting to a group channel is not supported.</exception>
-        Task<IAudioClient> IAudioChannel.ConnectAsync(bool selfDeaf, bool selfMute, bool external) { throw new NotSupportedException(); }
+        Task<IAudioClient> IAudioChannel.ConnectAsync(bool selfDeaf, bool selfMute, bool external, bool disconnect) { throw new NotSupportedException(); }
         Task IAudioChannel.DisconnectAsync() { throw new NotSupportedException(); }
         Task IAudioChannel.ModifyAsync(Action<AudioChannelProperties> func, RequestOptions options) { throw new NotSupportedException(); }
         #endregion

src/Discord.Net.WebSocket/Entities/Channels/SocketVoiceChannel.cs

@@ -89,8 +89,8 @@ namespace Discord.WebSocket
             => ChannelHelper.ModifyAsync(this, Discord, func, options);
 
         /// <inheritdoc />
-        public Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false)
+        public Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false, bool disconnect = true)
-            => Guild.ConnectAudioAsync(Id, selfDeaf, selfMute, external);
+            => Guild.ConnectAudioAsync(Id, selfDeaf, selfMute, external, disconnect);
 
         /// <inheritdoc />
         public Task DisconnectAsync()

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -1723,13 +1723,14 @@ namespace Discord.WebSocket
         {
             return _audioClient?.GetInputStream(userId);
         }
-        internal async Task<IAudioClient> ConnectAudioAsync(ulong channelId, bool selfDeaf, bool selfMute, bool external)
+        internal async Task<IAudioClient> ConnectAudioAsync(ulong channelId, bool selfDeaf, bool selfMute, bool external, bool disconnect = true)
         {
             TaskCompletionSource<AudioClient> promise;
 
             await _audioLock.WaitAsync().ConfigureAwait(false);
             try
             {
+                if (disconnect || !external)
                     await DisconnectAudioInternalAsync().ConfigureAwait(false);
                 promise = new TaskCompletionSource<AudioClient>();
                 _audioConnectPromise = promise;

test/Discord.Net.Tests.Unit/MockedEntities/MockedGroupChannel.cs

@@ -18,7 +18,7 @@ namespace Discord
 
         public string RTCRegion => throw new NotImplementedException();
 
-        public Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false)
+        public Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false, bool disconnect = true)
         {
             throw new NotImplementedException();
         }

test/Discord.Net.Tests.Unit/MockedEntities/MockedVoiceChannel.cs

@@ -53,7 +53,7 @@ namespace Discord
 
         public Task AddPermissionOverwriteAsync(IRole role, OverwritePermissions permissions, RequestOptions options = null) => throw new NotImplementedException();
         public Task AddPermissionOverwriteAsync(IUser user, OverwritePermissions permissions, RequestOptions options = null) => throw new NotImplementedException();
-        public Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false) => throw new NotImplementedException();
+        public Task<IAudioClient> ConnectAsync(bool selfDeaf = false, bool selfMute = false, bool external = false, bool disconnect = true) => throw new NotImplementedException();
         public Task<IInviteMetadata> CreateInviteAsync(int? maxAge = 86400, int? maxUses = null, bool isTemporary = false, bool isUnique = false, RequestOptions options = null) => throw new NotImplementedException();
         public Task<IInviteMetadata> CreateInviteToApplicationAsync(ulong applicationId, int? maxAge = 86400, int? maxUses = null, bool isTemporary = false, bool isUnique = false, RequestOptions options = null) => throw new NotImplementedException();
         public Task<IInviteMetadata> CreateInviteToApplicationAsync(DefaultApplications application, int? maxAge = 86400, int? maxUses = null, bool isTemporary = false, bool isUnique = false, RequestOptions options = null) => throw new NotImplementedException();