moved to List from ImmutableArray on json return type.

src/Compilers/Core/Portable/InternalUtilities/EnumerableExtensions.cs

@@ -3,9 +3,11 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Linq;
+using Microsoft.CodeAnalysis.PooledObjects;
 
 namespace Roslyn.Utilities
 {
@@ -242,6 +244,19 @@ public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T> source)
             return source.Where((Func<T, bool>)s_notNullTest);
         }
 
+        public static ImmutableArray<TResult> SelectAsArray<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector)
+        {
+            if (source == null)
+            {
+                return ImmutableArray<TResult>.Empty;
+            }
+
+            var builder = ArrayBuilder<TResult>.GetInstance();
+            builder.AddRange(source.Select(selector));
+
+            return builder.ToImmutableAndFree();
+        }
+
         public static bool All(this IEnumerable<bool> source)
         {
             if (source == null)

src/EditorFeatures/CSharpTest/AddUsing/AddUsingTests_NuGet.cs

@@ -257,16 +257,16 @@ await TestInRegularAndScriptAsync(
             installerServiceMock.Verify();
         }
 
-        private Task<ImmutableArray<PackageWithTypeResult>> CreateSearchResult(
+        private Task<IList<PackageWithTypeResult>> CreateSearchResult(
             string packageName, string typeName, ImmutableArray<string> containingNamespaceNames)
         {
             return CreateSearchResult(new PackageWithTypeResult(
                 packageName: packageName, typeName: typeName, version: null,
                 rank: 0, containingNamespaceNames: containingNamespaceNames));
         }
 
-        private Task<ImmutableArray<PackageWithTypeResult>> CreateSearchResult(params PackageWithTypeResult[] results)
-            => Task.FromResult(ImmutableArray.Create(results));
+        private Task<IList<PackageWithTypeResult>> CreateSearchResult(params PackageWithTypeResult[] results)
+            => Task.FromResult<IList<PackageWithTypeResult>>(ImmutableArray.Create(results));
 
         private ImmutableArray<string> CreateNameParts(params string[] parts) => parts.ToImmutableArray();
     }

src/EditorFeatures/Core/Implementation/TodoComment/TodoCommentIncrementalAnalyzer.cs

@@ -87,7 +87,7 @@ public async Task AnalyzeSyntaxAsync(Document document, InvocationReasons reason
             }
         }
 
-        private async Task<IList<TodoComment>> GetTodoCommentsAsync(Document document, ImmutableArray<TodoCommentDescriptor> tokens, CancellationToken cancellationToken)
+        private async Task<IList<TodoComment>> GetTodoCommentsAsync(Document document, IList<TodoCommentDescriptor> tokens, CancellationToken cancellationToken)
         {
             var service = document.GetLanguageService<ITodoCommentService>();
             if (service == null)

src/EditorFeatures/Core/SymbolSearch/SymbolSearchUpdateEngineFactory.cs

@@ -1,9 +1,11 @@
 // 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.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Remote;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.SymbolSearch
 {
@@ -61,31 +63,31 @@ public RemoteUpdateEngine(
             public async Task<ImmutableArray<PackageWithTypeResult>> FindPackagesWithTypeAsync(
                 string source, string name, int arity, CancellationToken cancellationToken)
             {
-                var results = await _session.TryInvokeAsync<ImmutableArray<PackageWithTypeResult>>(
+                var results = await _session.TryInvokeAsync<IList<PackageWithTypeResult>>(
                     nameof(IRemoteSymbolSearchUpdateEngine.FindPackagesWithTypeAsync),
                     new object[] { source, name, arity }, cancellationToken).ConfigureAwait(false);
 
-                return results.NullToEmpty();
+                return results.ToImmutableArrayOrEmpty();
             }
 
             public async Task<ImmutableArray<PackageWithAssemblyResult>> FindPackagesWithAssemblyAsync(
                 string source, string assemblyName, CancellationToken cancellationToken)
             {
-                var results = await _session.TryInvokeAsync<ImmutableArray<PackageWithAssemblyResult>>(
+                var results = await _session.TryInvokeAsync<IList<PackageWithAssemblyResult>>(
                     nameof(IRemoteSymbolSearchUpdateEngine.FindPackagesWithAssemblyAsync),
                     new object[] { source, assemblyName }, cancellationToken).ConfigureAwait(false);
 
-                return results.NullToEmpty();
+                return results.ToImmutableArrayOrEmpty();
             }
 
             public async Task<ImmutableArray<ReferenceAssemblyWithTypeResult>> FindReferenceAssembliesWithTypeAsync(
                 string name, int arity, CancellationToken cancellationToken)
             {
-                var results = await _session.TryInvokeAsync<ImmutableArray<ReferenceAssemblyWithTypeResult>>(
+                var results = await _session.TryInvokeAsync<IList<ReferenceAssemblyWithTypeResult>>(
                     nameof(IRemoteSymbolSearchUpdateEngine.FindReferenceAssembliesWithTypeAsync),
                     new object[] { name, arity }, cancellationToken).ConfigureAwait(false);
 
-                return results.NullToEmpty();
+                return results.ToImmutableArrayOrEmpty();
             }
 
             public async Task UpdateContinuouslyAsync(

src/EditorFeatures/VisualBasicTest/Diagnostics/AddImport/AddImportTests_NuGet.vb

@@ -239,7 +239,7 @@ End Class", fixProviderData:=New ProviderData(installerServiceMock.Object, packa
             installerServiceMock.Verify()
         End Function
 
-        Private Function CreateSearchResult(packageName As String, typeName As String, nameParts As ImmutableArray(Of String)) As Task(Of ImmutableArray(Of PackageWithTypeResult))
+        Private Function CreateSearchResult(packageName As String, typeName As String, nameParts As ImmutableArray(Of String)) As Task(Of IList(Of PackageWithTypeResult))
             Return CreateSearchResult(New PackageWithTypeResult(
                 packageName:=packageName,
                 typeName:=typeName,
@@ -248,8 +248,8 @@ End Class", fixProviderData:=New ProviderData(installerServiceMock.Object, packa
                 containingNamespaceNames:=nameParts))
         End Function
 
-        Private Function CreateSearchResult(ParamArray results As PackageWithTypeResult()) As Task(Of ImmutableArray(Of PackageWithTypeResult))
-            Return Task.FromResult(ImmutableArray.Create(results))
+        Private Function CreateSearchResult(ParamArray results As PackageWithTypeResult()) As Task(Of IList(Of PackageWithTypeResult))
+            Return Task.FromResult(Of IList(Of PackageWithTypeResult))(ImmutableArray.Create(results))
         End Function
 
         Private Function CreateNameParts(ParamArray parts As String()) As ImmutableArray(Of String)

src/Features/CSharp/Portable/TodoComments/CSharpTodoCommentIncrementalAnalyzerProvider.cs

@@ -28,7 +28,7 @@ public CSharpTodoCommentService(Workspace workspace) : base(workspace)
         {
         }
 
-        protected override void AppendTodoComments(ImmutableArray<TodoCommentDescriptor> commentDescriptors, SyntacticDocument document, SyntaxTrivia trivia, List<TodoComment> todoList)
+        protected override void AppendTodoComments(IList<TodoCommentDescriptor> commentDescriptors, SyntacticDocument document, SyntaxTrivia trivia, List<TodoComment> todoList)
         {
             if (PreprocessorHasComment(trivia))
             {

src/Features/Core/Portable/AddImport/AbstractAddImportFeatureService.cs

@@ -61,7 +61,7 @@ public async Task<ImmutableArray<AddImportFixData>> GetFixesAsync(
             if (RemoteSupportedLanguages.IsSupported(document.Project.Language))
             {
                 var callbackTarget = new RemoteSymbolSearchService(symbolSearchService, cancellationToken);
-                var result = await document.Project.Solution.TryRunCodeAnalysisRemoteAsync<ImmutableArray<AddImportFixData>>(
+                var result = await document.Project.Solution.TryRunCodeAnalysisRemoteAsync<IList<AddImportFixData>>(
                     RemoteFeatureOptions.AddImportEnabled,
                     callbackTarget,
                     nameof(IRemoteAddImportFeatureService.GetFixesAsync),
@@ -78,9 +78,9 @@ public async Task<ImmutableArray<AddImportFixData>> GetFixesAsync(
 
                 var documentOptions = await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
 
-                if (!result.IsDefault)
+                if (result != null)
                 {
-                    return result;
+                    return result.ToImmutableArray();
                 }
             }
 

src/Features/Core/Portable/AddImport/Remote/AbstractAddImportFeatureService_Remote.cs

@@ -1,6 +1,7 @@
 // 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.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -39,21 +40,21 @@ public Task UpdateContinuouslyAsync(string sourceName, string localSettingsDirec
                 throw new NotImplementedException();
             }
 
-            public Task<ImmutableArray<PackageWithTypeResult>> FindPackagesWithTypeAsync(
+            public Task<IList<PackageWithTypeResult>> FindPackagesWithTypeAsync(
                 string source, string name, int arity, CancellationToken cancellationToken)
             {
                 return _symbolSearchService.FindPackagesWithTypeAsync(
                     source, name, arity, cancellationToken);
             }
 
-            public Task<ImmutableArray<PackageWithAssemblyResult>> FindPackagesWithAssemblyAsync(
+            public Task<IList<PackageWithAssemblyResult>> FindPackagesWithAssemblyAsync(
                 string source, string name, CancellationToken cancellationToken)
             {
                 return _symbolSearchService.FindPackagesWithAssemblyAsync(
                     source, name, cancellationToken);
             }
 
-            public Task<ImmutableArray<ReferenceAssemblyWithTypeResult>> FindReferenceAssembliesWithTypeAsync(
+            public Task<IList<ReferenceAssemblyWithTypeResult>> FindReferenceAssembliesWithTypeAsync(
                 string name, int arity, CancellationToken cancellationToken)
             {
                 return _symbolSearchService.FindReferenceAssembliesWithTypeAsync(

src/Features/Core/Portable/AddImport/Remote/IRemoteAddImportFeatureService.cs

@@ -1,5 +1,6 @@
 // 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.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -10,8 +11,8 @@ namespace Microsoft.CodeAnalysis.AddImport
 {
     internal interface IRemoteAddImportFeatureService
     {
-        Task<ImmutableArray<AddImportFixData>> GetFixesAsync(
+        Task<IList<AddImportFixData>> GetFixesAsync(
             DocumentId documentId, TextSpan span, string diagnosticId, bool placeSystemNamespaceFirst,
-            bool searchReferenceAssemblies, ImmutableArray<PackageSource> packageSources, CancellationToken cancellationToken);
+            bool searchReferenceAssemblies, IList<PackageSource> packageSources, CancellationToken cancellationToken);
     }
 }

src/Features/Core/Portable/AddImport/SymbolReferenceFinder_PackageAssemblySearch.cs

@@ -5,6 +5,7 @@
 using Microsoft.CodeAnalysis.Packaging;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.SymbolSearch;
+using Microsoft.CodeAnalysis.Utilities;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.AddImport
@@ -90,7 +91,7 @@ private async Task FindReferenceAssemblyTypeReferencesAsync(
                 cancellationToken.ThrowIfCancellationRequested();
                 var results = await _symbolSearchService.FindReferenceAssembliesWithTypeAsync(
                     name, arity, cancellationToken).ConfigureAwait(false);
-                if (results.IsDefault)
+                if (results == null)
                 {
                     return;
                 }
@@ -121,7 +122,7 @@ private async Task FindNugetTypeReferencesAsync(
                 cancellationToken.ThrowIfCancellationRequested();
                 var results = await _symbolSearchService.FindPackagesWithTypeAsync(
                     source.Name, name, arity, cancellationToken).ConfigureAwait(false);
-                if (results.IsDefault)
+                if (results == null)
                 {
                     return;
                 }
@@ -163,7 +164,7 @@ private async Task HandleReferenceAssemblyReferenceAsync(
 
                 var desiredName = GetDesiredName(isAttributeSearch, result.TypeName);
                 allReferences.Add(new AssemblyReference(
-                    _owner, new SearchResult(desiredName, nameNode, result.ContainingNamespaceNames, weight), result));
+                    _owner, new SearchResult(desiredName, nameNode, result.ContainingNamespaceNames.ToReadOnlyList(), weight), result));
             }
 
             private void HandleNugetReference(
@@ -177,7 +178,7 @@ private void HandleNugetReference(
             {
                 var desiredName = GetDesiredName(isAttributeSearch, result.TypeName);
                 allReferences.Add(new PackageReference(_owner,
-                    new SearchResult(desiredName, nameNode, result.ContainingNamespaceNames, weight),
+                    new SearchResult(desiredName, nameNode, result.ContainingNamespaceNames.ToReadOnlyList(), weight),
                     source, result.PackageName, result.Version));
             }
 

src/Features/Core/Portable/DesignerAttributes/IRemoteDesignerAttributeService.cs

@@ -1,13 +1,13 @@
 // 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.Collections.Immutable;
+using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 
 namespace Microsoft.CodeAnalysis.DesignerAttributes
 {
     internal interface IRemoteDesignerAttributeService
     {
-        Task<ImmutableArray<DesignerAttributeDocumentData>> ScanDesignerAttributesAsync(ProjectId projectId, CancellationToken cancellationToken);
+        Task<IList<DesignerAttributeDocumentData>> ScanDesignerAttributesAsync(ProjectId projectId, CancellationToken cancellationToken);
     }
 }

src/Features/Core/Portable/DocumentHighlighting/AbstractDocumentHighlightsService.cs

@@ -39,7 +39,7 @@ public async Task<ImmutableArray<DocumentHighlights>> GetDocumentHighlightsAsync
         private async Task<(bool succeeded, ImmutableArray<DocumentHighlights> highlights)> GetDocumentHighlightsInRemoteProcessAsync(
             Document document, int position, IImmutableSet<Document> documentsToSearch, CancellationToken cancellationToken)
         {
-            var result = await document.Project.Solution.TryRunCodeAnalysisRemoteAsync<ImmutableArray<SerializableDocumentHighlights>>(
+            var result = await document.Project.Solution.TryRunCodeAnalysisRemoteAsync<IList<SerializableDocumentHighlights>>(
                 RemoteFeatureOptions.DocumentHighlightingEnabled,
                 nameof(IRemoteDocumentHighlights.GetDocumentHighlightsAsync),
                 new object[]
@@ -50,7 +50,7 @@ public async Task<ImmutableArray<DocumentHighlights>> GetDocumentHighlightsAsync
                 },
                 cancellationToken).ConfigureAwait(false);
 
-            if (result.IsDefault)
+            if (result == null)
             {
                 return (succeeded: false, ImmutableArray<DocumentHighlights>.Empty);
             }

src/Features/Core/Portable/DocumentHighlighting/IRemoteDocumentHighlights.cs

@@ -1,5 +1,6 @@
 // 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.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
@@ -9,17 +10,17 @@ namespace Microsoft.CodeAnalysis.DocumentHighlighting
 {
     internal interface IRemoteDocumentHighlights
     {
-        Task<ImmutableArray<SerializableDocumentHighlights>> GetDocumentHighlightsAsync(
+        Task<IList<SerializableDocumentHighlights>> GetDocumentHighlightsAsync(
             DocumentId documentId, int position, DocumentId[] documentIdsToSearch, CancellationToken cancellationToken);
     }
 
     internal struct SerializableDocumentHighlights
     {
         public DocumentId DocumentId;
-        public ImmutableArray<HighlightSpan> HighlightSpans;
+        public IList<HighlightSpan> HighlightSpans;
 
         public DocumentHighlights Rehydrate(Solution solution)
-            => new DocumentHighlights(solution.GetDocument(DocumentId), HighlightSpans);
+            => new DocumentHighlights(solution.GetDocument(DocumentId), HighlightSpans.ToImmutableArray());
 
         public static SerializableDocumentHighlights Dehydrate(DocumentHighlights highlights)
             => new SerializableDocumentHighlights

src/Features/Core/Portable/NavigateTo/AbstractNavigateToSearchService.Remote.cs

@@ -1,12 +1,14 @@
 // 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.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Experiments;
 using Microsoft.CodeAnalysis.Remote;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.NavigateTo
 {
@@ -17,23 +19,23 @@ private async Task<ImmutableArray<INavigateToSearchResult>> SearchDocumentInRemo
         {
             var solution = document.Project.Solution;
 
-            var serializableResults = await client.TryRunCodeAnalysisRemoteAsync<ImmutableArray<SerializableNavigateToSearchResult>>(
+            var serializableResults = await client.TryRunCodeAnalysisRemoteAsync<IList<SerializableNavigateToSearchResult>>(
                 solution, nameof(IRemoteNavigateToSearchService.SearchDocumentAsync),
                 new object[] { document.Id, searchPattern }, cancellationToken).ConfigureAwait(false);
 
-            return serializableResults.NullToEmpty().SelectAsArray(r => r.Rehydrate(solution));
+            return serializableResults.SelectAsArray(r => r.Rehydrate(solution));
         }
 
         private async Task<ImmutableArray<INavigateToSearchResult>> SearchProjectInRemoteProcessAsync(
             RemoteHostClient client, Project project, string searchPattern, CancellationToken cancellationToken)
         {
             var solution = project.Solution;
 
-            var serializableResults = await client.TryRunCodeAnalysisRemoteAsync<ImmutableArray<SerializableNavigateToSearchResult>>(
+            var serializableResults = await client.TryRunCodeAnalysisRemoteAsync<IList<SerializableNavigateToSearchResult>>(
                 solution, nameof(IRemoteNavigateToSearchService.SearchProjectAsync),
                 new object[] { project.Id, searchPattern }, cancellationToken).ConfigureAwait(false);
 
-            return serializableResults.NullToEmpty().SelectAsArray(r => r.Rehydrate(solution));
+            return serializableResults.SelectAsArray(r => r.Rehydrate(solution));
         }
 
         private static async Task<RemoteHostClient> TryGetRemoteHostClientAsync(Project project, CancellationToken cancellationToken)

src/Features/Core/Portable/NavigateTo/IRemoteNavigateToSearchService.cs

@@ -1,5 +1,6 @@
 // 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.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -9,7 +10,7 @@ namespace Microsoft.CodeAnalysis.NavigateTo
 {
     internal interface IRemoteNavigateToSearchService
     {
-        Task<ImmutableArray<SerializableNavigateToSearchResult>> SearchDocumentAsync(DocumentId documentId, string searchPattern, CancellationToken cancellationToken);
-        Task<ImmutableArray<SerializableNavigateToSearchResult>> SearchProjectAsync(ProjectId projectId, string searchPattern, CancellationToken cancellationToken);
+        Task<IList<SerializableNavigateToSearchResult>> SearchDocumentAsync(DocumentId documentId, string searchPattern, CancellationToken cancellationToken);
+        Task<IList<SerializableNavigateToSearchResult>> SearchProjectAsync(ProjectId projectId, string searchPattern, CancellationToken cancellationToken);
     }
 }