Allow IDocumentOptionsProviderFactories to optionally return providers

This renames Create to TryCreate.

src/EditorFeatures/Core.Wpf/Options/EditorConfigDocumentOptionsProviderFactory.cs

@@ -31,7 +31,7 @@ class EditorConfigDocumentOptionsProviderFactory : IDocumentOptionsProviderFacto
             _asynchronousOperationListenerProvider = asynchronousOperationListenerProvider;
         }
 
-        public IDocumentOptionsProvider Create(Workspace workspace)
+        public IDocumentOptionsProvider TryCreate(Workspace workspace)
         {
             ICodingConventionsManager codingConventionsManager;
 

src/VisualStudio/Core/Impl/RoslynVisualStudioWorkspace.cs

@@ -42,7 +42,12 @@ internal class RoslynVisualStudioWorkspace : VisualStudioWorkspaceImpl
 
             foreach (var providerFactory in documentOptionsProviderFactories)
             {
-                Services.GetRequiredService<IOptionService>().RegisterDocumentOptionsProvider(providerFactory.Create(this));
+                var optionsProvider = providerFactory.TryCreate(this);
+
+                if (optionsProvider != null)
+                {
+                    Services.GetRequiredService<IOptionService>().RegisterDocumentOptionsProvider(optionsProvider);
+                }
             }
         }
 

src/Workspaces/Core/Portable/Options/IDocumentOptionsProviderFactory.cs

@@ -8,6 +8,6 @@
     /// </remarks>
     interface IDocumentOptionsProviderFactory
     {
-        IDocumentOptionsProvider Create(Workspace workspace);
+        IDocumentOptionsProvider TryCreate(Workspace workspace);
     }
 }

src/Workspaces/Core/Portable/Options/OptionServiceFactory.cs

@@ -125,6 +125,11 @@ public OptionSet GetOptions()
 
             public void RegisterDocumentOptionsProvider(IDocumentOptionsProvider documentOptionsProvider)
             {
+                if (documentOptionsProvider == null)
+                {
+                    throw new ArgumentNullException(nameof(documentOptionsProvider));
+                }
+
                 lock (_gate)
                 {
                     _documentOptionsProviders = _documentOptionsProviders.Add(documentOptionsProvider);

src/Workspaces/Remote/Core/Services/RemoteWorkspace.cs

@@ -31,7 +31,12 @@ public RemoteWorkspace()
 
             foreach (var providerFactory in exportProvider.GetExports<IDocumentOptionsProviderFactory>())
             {
-                Services.GetRequiredService<IOptionService>().RegisterDocumentOptionsProvider(providerFactory.Value.Create(this));
+                var optionsProvider = providerFactory.Value.TryCreate(this);
+
+                if (optionsProvider != null)
+                {
+                    Services.GetRequiredService<IOptionService>().RegisterDocumentOptionsProvider(optionsProvider);
+                }
             }
 
             Options = Options.WithChangedOption(CacheOptions.RecoverableTreeLengthThreshold, 0);

src/Workspaces/Remote/Core/Services/TemporaryWorkspaceOptionsServiceFactory.cs

@@ -36,7 +36,12 @@ public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
 
             foreach (var factory in _documentOptionsProviderFactories)
             {
-                service.RegisterDocumentOptionsProvider(factory.Create(workspaceServices.Workspace));
+                var documentOptionsProvider = factory.TryCreate(workspaceServices.Workspace);
+
+                if (documentOptionsProvider != null)
+                {
+                    service.RegisterDocumentOptionsProvider(documentOptionsProvider);
+                }
             }
 
             return service;