cherry pick of 4.4 changes into master

libraries/Microsoft.Bot.Builder.Dialogs/Prompts/OAuthPrompt.cs

@@ -311,11 +311,32 @@ public OAuthPrompt(string dialogId, OAuthPromptSettings settings, PromptValidato
                     throw new InvalidOperationException("OAuthPrompt.Recognize(): not supported by the current adapter");
                 }
 
-                var token = await adapter.GetUserTokenAsync(turnContext, _settings.ConnectionName, magicCode, cancellationToken).ConfigureAwait(false);
-                if (token != null)
+                // Getting the token follows a different flow in Teams. At the signin completion, Teams
+                // will send the bot an "invoke" activity that contains a "magic" code. This code MUST
+                // then be used to try fetching the token from Botframework service within some time
+                // period. We try here. If it succeeds, we return 200 with an empty body. If it fails
+                // with a retriable error, we return 500. Teams will re-send another invoke in this case.
+                // If it failes with a non-retriable error, we return 404. Teams will not (still work in
+                // progress) retry in that case.
+                try
                 {
-                    result.Succeeded = true;
-                    result.Value = token;
+                    var token = await adapter.GetUserTokenAsync(turnContext, _settings.ConnectionName, magicCode, cancellationToken).ConfigureAwait(false);
+
+                    if (token != null)
+                    {
+                        result.Succeeded = true;
+                        result.Value = token;
+
+                        await turnContext.SendActivityAsync(new Activity { Type = ActivityTypesEx.InvokeResponse }, cancellationToken).ConfigureAwait(false);
+                    }
+                    else
+                    {
+                        await turnContext.SendActivityAsync(new Activity { Type = ActivityTypesEx.InvokeResponse, Value = new InvokeResponse { Status = 404 } }, cancellationToken).ConfigureAwait(false);
+                    }
+                }
+                catch
+                {
+                    await turnContext.SendActivityAsync(new Activity { Type = ActivityTypesEx.InvokeResponse, Value = new InvokeResponse { Status = 500 } }, cancellationToken).ConfigureAwait(false);
                 }
             }
             else if (turnContext.Activity.Type == ActivityTypes.Message)

libraries/integration/Microsoft.Bot.Builder.Integration.AspNet.Core/BotFrameworkHttpAdapter.cs

@@ -19,7 +19,17 @@ namespace Microsoft.Bot.Builder.Integration.AspNet.Core
     /// </summary>
     public class BotFrameworkHttpAdapter : BotFrameworkAdapter, IBotFrameworkHttpAdapter
     {
-        public BotFrameworkHttpAdapter(IConfiguration configuration, ILogger<BotFrameworkHttpAdapter> logger = null)
+        public BotFrameworkHttpAdapter(ICredentialProvider credentialProvider = null, IChannelProvider channelProvider = null, ILogger<BotFrameworkHttpAdapter> logger = null)
+            : base(credentialProvider ?? new SimpleCredentialProvider(), channelProvider, null, null, null, logger)
+        {
+        }
+
+        public BotFrameworkHttpAdapter(ICredentialProvider credentialProvider, IChannelProvider channelProvider, HttpClient httpClient, ILogger<BotFrameworkHttpAdapter> logger)
+            : base(credentialProvider ?? new SimpleCredentialProvider(), channelProvider, null, httpClient, null, logger)
+        {
+        }
+
+        protected BotFrameworkHttpAdapter(IConfiguration configuration, ILogger<BotFrameworkHttpAdapter> logger = null)
             : base(new ConfigurationCredentialProvider(configuration), new ConfigurationChannelProvider(configuration), customHttpClient: null, middleware: null, logger: logger)
         {
             var openIdEndpoint = configuration.GetSection(AuthenticationConstants.BotOpenIdMetadataKey)?.Value;
@@ -32,16 +42,6 @@ public BotFrameworkHttpAdapter(IConfiguration configuration, ILogger<BotFramewor
             }
         }
 
-        public BotFrameworkHttpAdapter(ICredentialProvider credentialProvider = null, IChannelProvider channelProvider = null, ILogger<BotFrameworkHttpAdapter> logger = null)
-            : base(credentialProvider ?? new SimpleCredentialProvider(), channelProvider, null, null, null, logger)
-        {
-        }
-
-        public BotFrameworkHttpAdapter(ICredentialProvider credentialProvider, IChannelProvider channelProvider, HttpClient httpClient, ILogger<BotFrameworkHttpAdapter> logger)
-            : base(credentialProvider ?? new SimpleCredentialProvider(), channelProvider, null, httpClient, null, logger)
-        {
-        }
-
         public async Task ProcessAsync(HttpRequest httpRequest, HttpResponse httpResponse, IBot bot, CancellationToken cancellationToken = default(CancellationToken))
         {
             if (httpRequest == null)

libraries/integration/Microsoft.Bot.Builder.Integration.AspNet.Core/HttpHelper.cs

@@ -56,14 +56,18 @@ public static void WriteResponse(HttpResponse response, InvokeResponse invokeRes
             }
             else
             {
-                response.ContentType = "application/json";
                 response.StatusCode = invokeResponse.Status;
 
-                using (var writer = new StreamWriter(response.Body))
+                if (invokeResponse.Body != null)
                 {
-                    using (var jsonWriter = new JsonTextWriter(writer))
+                    response.ContentType = "application/json";
+
+                    using (var writer = new StreamWriter(response.Body))
                     {
-                        BotMessageSerializer.Serialize(jsonWriter, invokeResponse.Body);
+                        using (var jsonWriter = new JsonTextWriter(writer))
+                        {
+                            BotMessageSerializer.Serialize(jsonWriter, invokeResponse.Body);
+                        }
                     }
                 }
             }

tests/integration/Microsoft.Bot.Builder.Integration.AspNet.Core.Tests/BotFrameworkHttpAdapterTests.cs

@@ -124,7 +124,7 @@ public void ConstructorWithConfiguration()
                 .Build();
 
             // Act
-            var adapter = new BotFrameworkHttpAdapter(configuration);
+            var adapter = new MyAdapter(configuration);
 
             // Assert
 
@@ -177,6 +177,14 @@ private static Stream CreateStream(Activity activity)
             return stream;
         }
 
+        private class MyAdapter : BotFrameworkHttpAdapter
+        {
+            public MyAdapter(IConfiguration configuration)
+                : base(configuration)
+            {
+            }
+        }
+
         private class InvokeResponseBot : IBot
         {
             public async Task OnTurnAsync(ITurnContext turnContext, CancellationToken cancellationToken = default(CancellationToken))