Make defaultValue a required parameter

for ExtensionManager.PerformFunction*()

Fixes internal TFS bug 1166482.

In cases where a fix provider throws an unhandled exception, ExtensionManager.PerformFunction*() was correctly handling the exception by displaying an 'info bar' alerting the user about the crash. However, because the defaultValue parameter for ExtensionManager.PerformFunction*() was optional, in some cases, we would end up returning default(ImmutableArray<T>) as opposed to ImmutableArray<T>.Empty to the VS platform's light bulb  engine. The difference is significant in this case since ImmutableArray<T> is a struct and since it is returned as an IEnumerable<T>. The platform code checks whether the returned IEnumerable<T> is 'null' (which it won't be) and then calls '.Any()' on it and this results in an InvalidOperationException from ImmutableArray<T>...

In addition to supplying the correct defaultValue of ImmutableArray<T>.Empty to avoid the above crash, I am also making defaultValue a required parameter (so that future consumers of ExtensionManager.PerformFunction*() don't run into this problem).

src/EditorFeatures/Core/Implementation/Suggestions/SuggestedAction.cs

@@ -122,7 +122,7 @@ public string DisplayText
                 // Underscores will become an accelerator in the VS smart tag.  So we double all
                 // underscores so they actually get represented as an underscore in the UI.
                 var extensionManager = this.Workspace.Services.GetService<IExtensionManager>();
-                var text = extensionManager.PerformFunction(Provider, () => CodeAction.Title, string.Empty);
+                var text = extensionManager.PerformFunction(Provider, () => CodeAction.Title, defaultValue: string.Empty);
                 return text.Replace("_", "__");
             }
         }
@@ -153,7 +153,7 @@ public virtual bool HasPreview
                 // 'null' / empty collection from within GetPreviewAsync().
 
                 return true;
-        }
+            }
         }
 
         public virtual async Task<object> GetPreviewAsync(CancellationToken cancellationToken)
@@ -184,7 +184,7 @@ public virtual async Task<object> GetPreviewAsync(CancellationToken cancellation
                 }
 
                 // GetPreviewPane() below needs to run on UI thread. We use ConfigureAwait(true) to stay on the UI thread.
-            }).ConfigureAwait(true);
+            }, defaultValue: null).ConfigureAwait(true);
 
             var previewPaneService = Workspace.Services.GetService<IPreviewPaneService>();
             if (previewPaneService == null)
@@ -216,7 +216,7 @@ public virtual bool HasActionSets
             {
                 return false;
             }
-            }
+        }
 
         public virtual Task<IEnumerable<SuggestedActionSet>> GetActionSetsAsync(CancellationToken cancellationToken)
         {

src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionWithFlavors.cs

@@ -50,8 +50,8 @@ public async override Task<IEnumerable<SuggestedActionSet>> GetActionSetsAsync(C
             // Light bulb will always invoke this property on the UI thread.
             AssertIsForeground();
 
-                if (_actionSets == null)
-                {
+            if (_actionSets == null)
+            {
                 var extensionManager = this.Workspace.Services.GetService<IExtensionManager>();
 
                 _actionSets = await extensionManager.PerformFunctionAsync(Provider, async () =>
@@ -75,12 +75,12 @@ public async override Task<IEnumerable<SuggestedActionSet>> GetActionSetsAsync(C
 
                     return builder.ToImmutable();
                     // We use ConfigureAwait(true) to stay on the UI thread.
-                }).ConfigureAwait(true);
-                }
-
-                return _actionSets;
+                }, defaultValue: ImmutableArray<SuggestedActionSet>.Empty).ConfigureAwait(true);
             }
 
+            return _actionSets;
+        }
+
         private async Task<SuggestedActionSet> GetPreviewChangesSuggestedActionSetAsync(CancellationToken cancellationToken)
         {
             var previewResult = await GetPreviewResultAsync(cancellationToken).ConfigureAwait(true);

src/Features/Core/CodeFixes/CodeFixService.cs

@@ -220,6 +220,7 @@ public async Task<IEnumerable<CodeFixCollection>> GetFixesAsync(Document documen
                         await task.ConfigureAwait(false);
                         return fixes;
                     };
+
                 await AppendFixesOrSuppressionsAsync(document, span, diagnostics, result, fixer,
                     hasFix, getFixes, cancellationToken).ConfigureAwait(false);
             }
@@ -261,8 +262,10 @@ public async Task<IEnumerable<CodeFixCollection>> GetFixesAsync(Document documen
                 // this can happen for suppression case where all diagnostics can't be suppressed
                 return result;
             }
+
             var extensionManager = document.Project.Solution.Workspace.Services.GetService<IExtensionManager>();
-            var fixes = await extensionManager.PerformFunctionAsync(fixer, () => getFixes(diagnostics)).ConfigureAwait(false);
+            var fixes = await extensionManager.PerformFunctionAsync(fixer, () => getFixes(diagnostics), defaultValue: SpecializedCollections.EmptyEnumerable<CodeFix>()).ConfigureAwait(false);
+
             if (fixes != null && fixes.Any())
             {
                 FixAllCodeActionContext fixAllContext = null;
@@ -270,7 +273,8 @@ public async Task<IEnumerable<CodeFixCollection>> GetFixesAsync(Document documen
                 if (codeFixProvider != null)
                 {
                     // If the codeFixProvider supports fix all occurrences, then get the corresponding FixAllProviderInfo and fix all context.
-                    var fixAllProviderInfo = extensionManager.PerformFunction(codeFixProvider, () => ImmutableInterlocked.GetOrAdd(ref _fixAllProviderMap, codeFixProvider, FixAllProviderInfo.Create));
+                    var fixAllProviderInfo = extensionManager.PerformFunction(codeFixProvider, () => ImmutableInterlocked.GetOrAdd(ref _fixAllProviderMap, codeFixProvider, FixAllProviderInfo.Create), defaultValue: null);
+
                     if (fixAllProviderInfo != null)
                     {
                         fixAllContext = new FixAllCodeActionContext(document, fixAllProviderInfo, codeFixProvider, diagnostics, this.GetDocumentDiagnosticsAsync, this.GetProjectDiagnosticsAsync, cancellationToken);
@@ -409,7 +413,7 @@ private ImmutableArray<DiagnosticId> GetFixableDiagnosticIds(CodeFixProvider fix
                 return extensionManager.PerformFunction(
                     fixer,
                     () => ImmutableInterlocked.GetOrAdd(ref _fixerToFixableIdsMap, fixer, f => f.FixableDiagnosticIds),
-                    ImmutableArray<DiagnosticId>.Empty);
+                    defaultValue: ImmutableArray<DiagnosticId>.Empty);
             }
 
             try

src/Workspaces/Core/Portable/ExtensionManager/IExtensionManagerExtensions.cs

@@ -36,7 +36,7 @@ public static void PerformAction(this IExtensionManager extensionManager, object
             this IExtensionManager extensionManager,
             object extension,
             Func<T> function,
-            T defaultValue = default(T))
+            T defaultValue)
         {
             try
             {
@@ -84,7 +84,7 @@ public static void PerformAction(this IExtensionManager extensionManager, object
             this IExtensionManager extensionManager,
             object extension,
             Func<Task<T>> function,
-            T defaultValue = default(T))
+            T defaultValue)
         {
             try
             {
@@ -115,7 +115,7 @@ public static void PerformAction(this IExtensionManager extensionManager, object
                 t1 =>
                 {
                     var query = from e in extensions
-                                let types = extensionManager.PerformFunction(e, () => nodeTypeGetter(e))
+                                let types = extensionManager.PerformFunction(e, () => nodeTypeGetter(e), defaultValue: SpecializedCollections.EmptyEnumerable<Type>())
                                 where types != null
                                 where !types.Any() || types.Any(t2 => t1 == t2 || t1.GetTypeInfo().IsSubclassOf(t2))
                                 select e;
@@ -134,7 +134,7 @@ public static void PerformAction(this IExtensionManager extensionManager, object
                 k =>
                 {
                     var query = from e in extensions
-                                let kinds = extensionManager.PerformFunction(e, () => tokenKindGetter(e))
+                                let kinds = extensionManager.PerformFunction(e, () => tokenKindGetter(e), defaultValue: SpecializedCollections.EmptyEnumerable<int>())
                                 where kinds != null
                                 where !kinds.Any() || kinds.Contains(k)
                                 select e;