Implement External Access APIs for Apex

src/Tools/ExternalAccess/Apex/ApexAsynchronousOperationListenerProviderAccessor.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System;
+using System.Composition;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Shared.TestHooks;
+
+namespace Microsoft.CodeAnalysis.ExternalAccess.Apex
+{
+    [Export(typeof(IApexAsynchronousOperationListenerProviderAccessor))]
+    [Shared]
+    internal sealed class ApexAsynchronousOperationListenerProviderAccessor : IApexAsynchronousOperationListenerProviderAccessor
+    {
+        private readonly AsynchronousOperationListenerProvider _implementation;
+
+        [ImportingConstructor]
+        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
+        public ApexAsynchronousOperationListenerProviderAccessor(AsynchronousOperationListenerProvider implementation)
+        {
+            _implementation = implementation;
+        }
+
+        public Task WaitAllAsync(string[] featureNames = null, Action eventProcessingAction = null)
+            => _implementation.WaitAllAsync(featureNames, eventProcessingAction);
+    }
+}

src/Tools/ExternalAccess/Apex/IApexAsynchronousOperationListenerProviderAccessor.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System;
+using System.Threading.Tasks;
+
+namespace Microsoft.CodeAnalysis.ExternalAccess.Apex
+{
+    internal interface IApexAsynchronousOperationListenerProviderAccessor
+    {
+        Task WaitAllAsync(string[] featureNames = null, Action eventProcessingAction = null);
+    }
+}

src/Tools/ExternalAccess/Apex/Microsoft.CodeAnalysis.ExternalAccess.Apex.csproj

@@ -24,6 +24,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\..\Compilers\Core\Portable\Microsoft.CodeAnalysis.csproj" />
+    <ProjectReference Include="..\..\..\Workspaces\Core\Portable\Microsoft.CodeAnalysis.Workspaces.csproj" />
   </ItemGroup>
 
   <ItemGroup>

src/Workspaces/Core/Portable/Microsoft.CodeAnalysis.Workspaces.csproj

@@ -232,6 +232,7 @@
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.EditorFeatures" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.EditorFeatures.Text" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.EditorFeatures.Wpf" />
+    <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.Apex" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.Debugger" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.ExternalAccess.UnitTesting" />
     <InternalsVisibleTo Include="Microsoft.CodeAnalysis.Features" />