[UWP] Fix null dereference in Media code path

source/uwp/Renderer/lib/ActionHelpers.cpp

@@ -278,14 +278,12 @@ namespace AdaptiveNamespace::ActionHelpers
     {
         // determine what type of action we're building
         ComPtr<IAdaptiveActionElement> action(adaptiveActionElement);
-        ABI::AdaptiveNamespace::ActionType actionType;
-        RETURN_IF_FAILED(action->get_ActionType(&actionType));
 
         // now construct an appropriate button for the action type
         ComPtr<IButton> button;
         try
         {
-            CreateAppropriateButton(actionType, button);
+            CreateAppropriateButton(action.Get(), button);
         }
         CATCH_RETURN;
 
@@ -621,11 +619,8 @@ namespace AdaptiveNamespace::ActionHelpers
             return;
         }
 
-        ABI::AdaptiveNamespace::ActionType actionType;
-        action->get_ActionType(&actionType);
-
         ComPtr<IButton> button;
-        CreateAppropriateButton(actionType, button);
+        CreateAppropriateButton(action, button);
 
         ComPtr<IContentControl> buttonAsContentControl;
         THROW_IF_FAILED(button.As(&buttonAsContentControl));
@@ -1028,19 +1023,25 @@ namespace AdaptiveNamespace::ActionHelpers
         return actionSetAsPanel.CopyTo(actionSetControl);
     }
 
-    void CreateAppropriateButton(ABI::AdaptiveNamespace::ActionType actionType, ComPtr<IButton>& button)
+    void CreateAppropriateButton(ABI::AdaptiveNamespace::IAdaptiveActionElement* action, ComPtr<IButton>& button)
     {
-        // construct an appropriate button for the action type
-        if (actionType == ABI::AdaptiveNamespace::ActionType_OpenUrl)
+        if (action != nullptr)
         {
-            // OpenUrl buttons should appear as links for accessibility purposes, so we use our custom LinkButton.
-            auto linkButton = winrt::make<LinkButton>();
-            button = linkButton.as<IButton>().detach();
+            ABI::AdaptiveNamespace::ActionType actionType;
+            THROW_IF_FAILED(action->get_ActionType(&actionType));
+
+            // construct an appropriate button for the action type
+            if (actionType == ABI::AdaptiveNamespace::ActionType_OpenUrl)
+            {
+                // OpenUrl buttons should appear as links for accessibility purposes, so we use our custom LinkButton.
+                auto linkButton = winrt::make<LinkButton>();
+                button = linkButton.as<IButton>().detach();
+            }
         }
 
         if (!button)
         {
-            // Either non-OpenUrl action or instantiating LinkButton failed. Use standard button.
+            // Either no action, non-OpenUrl action, or instantiating LinkButton failed. Use standard button.
             button = XamlHelpers::CreateXamlClass<IButton>(HStringReference(RuntimeClass_Windows_UI_Xaml_Controls_Button));
         }
     }

source/uwp/Renderer/lib/ActionHelpers.h

@@ -71,6 +71,6 @@ namespace AdaptiveNamespace::ActionHelpers
                                  _In_ ABI::AdaptiveNamespace::IAdaptiveRenderArgs* renderArgs,
                                  _Outptr_ ABI::Windows::UI::Xaml::IUIElement** actionSetControl);
 
-    void CreateAppropriateButton(ABI::AdaptiveNamespace::ActionType actionType,
+    void CreateAppropriateButton(_In_ ABI::AdaptiveNamespace::IAdaptiveActionElement* action,
                                  Microsoft::WRL::ComPtr<ABI::Windows::UI::Xaml::Controls::IButton>& button);
 }

source/uwp/UWPUnitTests/RenderTests.cs

@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using Windows.ApplicationModel.Core;
+using Windows.UI.Core;
+using System.Threading.Tasks;
+using UWPTestLibrary;
+using AdaptiveCards.Rendering.Uwp;
+
+namespace UWPUnitTests
+{
+    [TestClass]
+    public class RenderTests
+    {
+        [TestMethod]
+        public async Task Media()
+        {
+            AdaptiveCard card = new AdaptiveCard
+            {
+                Version = "1.3"
+            };
+
+            AdaptiveMediaSource mediaSource = new AdaptiveMediaSource
+            {
+                MimeType = "audio/mp4",
+                Url = "https://www.stuff.com/media.mp4"
+            };
+
+            AdaptiveMedia media = new AdaptiveMedia();
+            media.Sources.Add(mediaSource);
+
+            card.Body.Add(media);
+
+            await RenderInDispatcher(card);
+        }
+
+        public async Task RenderInDispatcher(AdaptiveCard card)
+        {
+            RenderedAdaptiveCard renderedCard = null;
+
+            // Need to move the test to the UI Thread to render the card
+            var dispatcher = CoreApplication.MainView.CoreWindow.Dispatcher;
+            await dispatcher.RunAsync(CoreDispatcherPriority.Normal, async () =>
+            {
+                var renderer = new AdaptiveCardRenderer();
+
+                renderedCard = renderer.RenderAdaptiveCard(card);
+            });
+
+            Assert.AreEqual(0, renderedCard.Warnings.Count);
+            Assert.AreEqual(0, renderedCard.Errors.Count);
+        }
+    }
+}

source/uwp/UWPUnitTests/UWPUnitTests.csproj

@@ -126,6 +126,7 @@
       <DependentUpon>App.xaml</DependentUpon>
     </Compile>
     <Compile Include="RendererRegistration.cs" />
+    <Compile Include="RenderTests.cs" />
     <Compile Include="UnitTest.cs" />
   </ItemGroup>
   <ItemGroup>
@@ -245,4 +246,4 @@
   <Target Name="AfterBuild">
   </Target>
   -->
-</Project>
+</Project>