Merge pull request #47294 from sharwell/codefixes-annotations

Update nullable annotations in CodeFixes folder

src/EditorFeatures/Core/Implementation/CodeFixes/CodeFixService.cs

@@ -58,7 +58,7 @@ internal partial class CodeFixService : ForegroundThreadAffinitizedObject, ICode
         private readonly ImmutableDictionary<LanguageKind, Lazy<ImmutableArray<IConfigurationFixProvider>>> _configurationProvidersMap;
         private readonly IEnumerable<Lazy<IErrorLoggerService>> _errorLoggers;
 
-        private ImmutableDictionary<object, FixAllProviderInfo> _fixAllProviderMap;
+        private ImmutableDictionary<object, FixAllProviderInfo?> _fixAllProviderMap;
 
         [ImportingConstructor]
         [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
@@ -85,7 +85,7 @@ internal partial class CodeFixService : ForegroundThreadAffinitizedObject, ICode
             _projectFixersMap = new ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, ImmutableDictionary<string, List<CodeFixProvider>>>();
             _analyzerReferenceToFixersMap = new ConditionalWeakTable<AnalyzerReference, ProjectCodeFixProvider>();
             _createProjectCodeFixProvider = new ConditionalWeakTable<AnalyzerReference, ProjectCodeFixProvider>.CreateValueCallback(r => new ProjectCodeFixProvider(r));
-            _fixAllProviderMap = ImmutableDictionary<object, FixAllProviderInfo>.Empty;
+            _fixAllProviderMap = ImmutableDictionary<object, FixAllProviderInfo?>.Empty;
         }
 
         public async Task<FirstDiagnosticResult> GetMostSevereFixableDiagnosticAsync(

src/Features/CSharp/Portable/CodeFixes/Nullable/CSharpDeclareAsNullableCodeFixProvider.cs

@@ -128,7 +128,7 @@ static bool IsRemoteApiUsage(SyntaxNode node, SemanticModel model)
             }
         }
 
-        protected override bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic, Document document, SemanticModel model, string equivalenceKey, CancellationToken cancellationToken)
+        protected override bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic, Document document, SemanticModel model, string? equivalenceKey, CancellationToken cancellationToken)
         {
             var node = diagnostic.Location.FindNode(getInnermostNodeForTie: true, cancellationToken);
             return equivalenceKey == GetEquivalenceKey(node, model);

src/Features/Core/Portable/ConflictMarkerResolution/AbstractConflictMarkerCodeFixProvider.cs

@@ -293,7 +293,7 @@ private static int GetEndIncludingLineBreak(SourceText text, int position)
 
         private async Task<SyntaxNode> FixAllAsync(
             Document document, ImmutableArray<Diagnostic> diagnostics,
-            string equivalenceKey, CancellationToken cancellationToken)
+            string? equivalenceKey, CancellationToken cancellationToken)
         {
             Debug.Assert(
                 equivalenceKey == TakeTopEquivalenceKey ||

src/Workspaces/Core/Portable/CodeFixes/CodeFixContext.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -123,15 +125,6 @@ public struct CodeFixContext : ITypeScriptCodeFixContext
         {
         }
 
-        internal CodeFixContext(
-            Project project,
-            ImmutableArray<Diagnostic> diagnostics,
-            Action<CodeAction, ImmutableArray<Diagnostic>> registerCodeFix,
-            CancellationToken cancellationToken)
-            : this(document: null, project: project, span: default, diagnostics: diagnostics, registerCodeFix: registerCodeFix, verifyArguments: false, isBlocking: false, cancellationToken: cancellationToken)
-        {
-        }
-
         private CodeFixContext(
             Document document,
             Project project,

src/Workspaces/Core/Portable/CodeFixes/CodeFixProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading.Tasks;
 
@@ -32,7 +34,7 @@ public abstract class CodeFixProvider
         /// Return null if the provider doesn't support fix all/multiple occurrences.
         /// Otherwise, you can return any of the well known fix all providers from <see cref="WellKnownFixAllProviders"/> or implement your own fix all provider.
         /// </summary>
-        public virtual FixAllProvider GetFixAllProvider()
+        public virtual FixAllProvider? GetFixAllProvider()
             => null;
     }
 }

src/Workspaces/Core/Portable/CodeFixes/ExportCodeFixProviderAttribute.cs

@@ -2,8 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Composition;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.CodeAnalysis.CodeFixes
 {
@@ -17,7 +20,8 @@ public sealed class ExportCodeFixProviderAttribute : ExportAttribute
         /// <summary>
         /// Optional name of the <see cref="CodeFixProvider"/>.  
         /// </summary>
-        public string Name { get; set; }
+        [DisallowNull]
+        public string? Name { get; set; }
 
         /// <summary>
         /// The source languages this provider can provide fixes for.  See <see cref="LanguageNames"/>.
@@ -39,8 +43,6 @@ public sealed class ExportCodeFixProviderAttribute : ExportAttribute
                 throw new ArgumentNullException(nameof(additionalLanguages));
             }
 
-            this.Name = null;
-
             var languages = new string[additionalLanguages.Length + 1];
             languages[0] = firstLanguage ?? throw new ArgumentNullException(nameof(firstLanguage));
             for (var index = 0; index < additionalLanguages.Length; index++)

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/BatchFixAllProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
@@ -14,6 +16,7 @@
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Collections;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
@@ -30,7 +33,7 @@ internal partial class BatchFixAllProvider : FixAllProvider
 
         #region "AbstractFixAllProvider methods"
 
-        public override async Task<CodeAction> GetFixAsync(FixAllContext fixAllContext)
+        public override async Task<CodeAction?> GetFixAsync(FixAllContext fixAllContext)
         {
             if (fixAllContext.Document != null)
             {
@@ -46,7 +49,7 @@ public override async Task<CodeAction> GetFixAsync(FixAllContext fixAllContext)
 
         #endregion
 
-        private async Task<CodeAction> GetFixAsync(
+        private async Task<CodeAction?> GetFixAsync(
             ImmutableDictionary<Document, ImmutableArray<Diagnostic>> documentsAndDiagnosticsToFixMap,
             FixAllState fixAllState, CancellationToken cancellationToken)
         {
@@ -131,7 +134,7 @@ public override async Task<CodeAction> GetFixAsync(FixAllContext fixAllContext)
             await Task.WhenAll(fixerTasks).ConfigureAwait(false);
         }
 
-        private async Task<CodeAction> GetFixAsync(
+        private async Task<CodeAction?> GetFixAsync(
             ImmutableDictionary<Project, ImmutableArray<Diagnostic>> projectsAndDiagnosticsToFixMap,
             FixAllState fixAllState, CancellationToken cancellationToken)
         {
@@ -198,19 +201,10 @@ public override async Task<CodeAction> GetFixAsync(FixAllContext fixAllContext)
             ConcurrentBag<(Diagnostic diagnostic, CodeAction action)> fixes,
             FixAllState fixAllState, CancellationToken cancellationToken)
         {
-            Debug.Assert(!diagnostics.IsDefault);
-            cancellationToken.ThrowIfCancellationRequested();
-
-            var registerCodeFix = GetRegisterCodeFixAction(fixAllState, fixes);
-            var context = new CodeFixContext(
-                project, diagnostics, registerCodeFix, cancellationToken);
-
-            // TODO: Wrap call to ComputeFixesAsync() below in IExtensionManager.PerformFunctionAsync() so that
-            // a buggy extension that throws can't bring down the host?
-            return fixAllState.CodeFixProvider.RegisterCodeFixesAsync(context) ?? Task.CompletedTask;
+            return Task.CompletedTask;
         }
 
-        public virtual async Task<CodeAction> TryGetMergedFixAsync(
+        public virtual async Task<CodeAction?> TryGetMergedFixAsync(
             ImmutableArray<(Diagnostic diagnostic, CodeAction action)> batchOfFixes,
             FixAllState fixAllState, CancellationToken cancellationToken)
         {
@@ -337,8 +331,8 @@ public virtual string GetFixAllTitle(FixAllState fixAllState)
 
             var totalChangesIntervalTree = SimpleIntervalTree.Create(new TextChangeIntervalIntrospector(), Array.Empty<TextChange>());
 
-            var oldDocument = oldSolution.GetDocument(orderedDocuments[0].document.Id);
-            var differenceService = oldSolution.Workspace.Services.GetService<IDocumentTextDifferencingService>();
+            var oldDocument = oldSolution.GetRequiredDocument(orderedDocuments[0].document.Id);
+            var differenceService = oldSolution.Workspace.Services.GetRequiredService<IDocumentTextDifferencingService>();
 
             foreach (var (_, currentDocument) in orderedDocuments)
             {
@@ -381,6 +375,11 @@ public virtual string GetFixAllTitle(FixAllState fixAllState)
 
             var changedSolution = await codeAction.GetChangedSolutionInternalAsync(
                 cancellationToken: cancellationToken).ConfigureAwait(false);
+            if (changedSolution is null)
+            {
+                // No changed documents
+                return;
+            }
 
             var solutionChanges = new SolutionChanges(changedSolution, oldSolution);
 
@@ -393,7 +392,7 @@ public virtual string GetFixAllTitle(FixAllState fixAllState)
 
             foreach (var documentId in documentIdsWithChanges)
             {
-                var changedDocument = changedSolution.GetDocument(documentId);
+                var changedDocument = changedSolution.GetRequiredDocument(documentId);
 
                 documentIdToChangedDocuments.GetOrAdd(documentId, s_getValue).Add(
                     (codeAction, changedDocument));

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllContext.DiagnosticProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllContext.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -21,7 +23,7 @@ public partial class FixAllContext
     {
         internal FixAllState State { get; }
 
-        internal FixAllProvider FixAllProvider => State.FixAllProvider;
+        internal FixAllProvider? FixAllProvider => State.FixAllProvider;
 
         /// <summary>
         /// Solution to fix all occurrences.
@@ -37,7 +39,7 @@ public partial class FixAllContext
         /// Document within which fix all occurrences was triggered.
         /// Can be null if the context was created using <see cref="FixAllContext.FixAllContext(Project, CodeFixProvider, FixAllScope, string, IEnumerable{string}, DiagnosticProvider, CancellationToken)"/>.
         /// </summary>
-        public Document Document => State.Document;
+        public Document? Document => State.Document;
 
         /// <summary>
         /// Underlying <see cref="CodeFixes.CodeFixProvider"/> which triggered this fix all.
@@ -59,7 +61,7 @@ public partial class FixAllContext
         /// <summary>
         /// The <see cref="CodeAction.EquivalenceKey"/> value expected of a <see cref="CodeAction"/> participating in this fix all.
         /// </summary>
-        public string CodeActionEquivalenceKey => State.CodeActionEquivalenceKey;
+        public string? CodeActionEquivalenceKey => State.CodeActionEquivalenceKey;
 
         /// <summary>
         /// CancellationToken for fix all session.

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllLogger.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Linq;
 using Microsoft.CodeAnalysis.Internal.Log;
@@ -52,7 +54,7 @@ public static void LogState(FixAllState fixAllState, bool isInternalCodeFixProvi
                 }
                 else
                 {
-                    m[CodeFixProvider] = fixAllState.CodeFixProvider.GetType().FullName.GetHashCode().ToString();
+                    m[CodeFixProvider] = fixAllState.CodeFixProvider.GetType().FullName!.GetHashCode().ToString();
                     m[CodeActionEquivalenceKey] = fixAllState.CodeActionEquivalenceKey?.GetHashCode().ToString();
                     m[LanguageName] = fixAllState.Project.Language.GetHashCode().ToString();
                 }

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading.Tasks;
@@ -36,6 +38,6 @@ public virtual IEnumerable<string> GetSupportedFixAllDiagnosticIds(CodeFixProvid
         /// <summary>
         /// Gets fix all occurrences fix for the given fixAllContext.
         /// </summary>
-        public abstract Task<CodeAction> GetFixAsync(FixAllContext fixAllContext);
+        public abstract Task<CodeAction?> GetFixAsync(FixAllContext fixAllContext);
     }
 }

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllProviderInfo.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -28,7 +30,7 @@ internal abstract class FixAllProviderInfo
         /// <summary>
         /// Gets an optional <see cref="FixAllProviderInfo"/> for the given code fix provider or suppression fix provider.
         /// </summary>
-        public static FixAllProviderInfo Create(object provider)
+        public static FixAllProviderInfo? Create(object provider)
         {
             if (provider is CodeFixProvider codeFixProvider)
             {
@@ -41,7 +43,7 @@ public static FixAllProviderInfo Create(object provider)
         /// <summary>
         /// Gets an optional <see cref="FixAllProviderInfo"/> for the given code fix provider.
         /// </summary>
-        private static FixAllProviderInfo CreateWithCodeFixer(CodeFixProvider provider)
+        private static FixAllProviderInfo? CreateWithCodeFixer(CodeFixProvider provider)
         {
             var fixAllProvider = provider.GetFixAllProvider();
             if (fixAllProvider == null)
@@ -67,7 +69,7 @@ private static FixAllProviderInfo CreateWithCodeFixer(CodeFixProvider provider)
         /// <summary>
         /// Gets an optional <see cref="FixAllProviderInfo"/> for the given suppression fix provider.
         /// </summary>
-        private static FixAllProviderInfo CreateWithSuppressionFixer(IConfigurationFixProvider provider)
+        private static FixAllProviderInfo? CreateWithSuppressionFixer(IConfigurationFixProvider provider)
         {
             var fixAllProvider = provider.GetFixAllProvider();
             if (fixAllProvider == null)

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/FixAllScope.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 namespace Microsoft.CodeAnalysis.CodeFixes
 {
     /// <summary>

src/Workspaces/Core/Portable/CodeFixes/FixAllOccurrences/WellKnownFixAllProviders.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using Microsoft.CodeAnalysis.CodeActions;
 
 namespace Microsoft.CodeAnalysis.CodeFixes

src/Workspaces/Core/Portable/CodeFixes/Supression/IConfigurationFixProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;
@@ -38,6 +40,6 @@ internal interface IConfigurationFixProvider
         /// Return null if the provider doesn't support fix all/multiple occurrences.
         /// Otherwise, you can return any of the well known fix all providers from <see cref="WellKnownFixAllProviders"/> or implement your own fix all provider.
         /// </summary>
-        FixAllProvider GetFixAllProvider();
+        FixAllProvider? GetFixAllProvider();
     }
 }

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CodeFixCategory.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 namespace Microsoft.CodeAnalysis.CodeFixes
 {
     /// <summary>

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/CustomCodeActions.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Threading;
 using System.Threading.Tasks;
@@ -13,24 +15,21 @@ internal static class CustomCodeActions
     {
         internal abstract class SimpleCodeAction : CodeAction
         {
-            public SimpleCodeAction(string title, string equivalenceKey)
+            public SimpleCodeAction(string title, string? equivalenceKey)
             {
                 Title = title;
                 EquivalenceKey = equivalenceKey;
             }
 
             public sealed override string Title { get; }
-            public sealed override string EquivalenceKey { get; }
-
-            protected override Task<Document> GetChangedDocumentAsync(CancellationToken cancellationToken)
-                => SpecializedTasks.Null<Document>();
+            public sealed override string? EquivalenceKey { get; }
         }
 
         internal class DocumentChangeAction : SimpleCodeAction
         {
             private readonly Func<CancellationToken, Task<Document>> _createChangedDocument;
 
-            public DocumentChangeAction(string title, Func<CancellationToken, Task<Document>> createChangedDocument, string equivalenceKey = null)
+            public DocumentChangeAction(string title, Func<CancellationToken, Task<Document>> createChangedDocument, string? equivalenceKey = null)
                 : base(title, equivalenceKey)
             {
                 _createChangedDocument = createChangedDocument;
@@ -44,14 +43,14 @@ internal class SolutionChangeAction : SimpleCodeAction
         {
             private readonly Func<CancellationToken, Task<Solution>> _createChangedSolution;
 
-            public SolutionChangeAction(string title, Func<CancellationToken, Task<Solution>> createChangedSolution, string equivalenceKey = null)
+            public SolutionChangeAction(string title, Func<CancellationToken, Task<Solution>> createChangedSolution, string? equivalenceKey = null)
                 : base(title, equivalenceKey)
             {
                 _createChangedSolution = createChangedSolution;
             }
 
-            protected override Task<Solution> GetChangedSolutionAsync(CancellationToken cancellationToken)
-                => _createChangedSolution(cancellationToken);
+            protected override Task<Solution?> GetChangedSolutionAsync(CancellationToken cancellationToken)
+                => _createChangedSolution(cancellationToken).AsNullable();
         }
     }
 }

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/DocumentBasedFixAllProvider.cs

@@ -9,10 +9,7 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeActions;
 using Microsoft.CodeAnalysis.PooledObjects;
-
-#if NETSTANDARD2_0
 using Roslyn.Utilities;
-#endif
 
 #pragma warning disable RS0005 // Do not use generic CodeAction.Create to create CodeAction
 
@@ -78,6 +75,8 @@ internal abstract class DocumentBasedFixAllProvider : FixAllProvider
 
         private async Task<Document> GetDocumentFixesAsync(FixAllContext fixAllContext)
         {
+            RoslynDebug.AssertNotNull(fixAllContext.Document);
+
             var documentDiagnosticsToFix = await FixAllContextHelper.GetDocumentDiagnosticsToFixAsync(fixAllContext, progressTrackerOpt: null).ConfigureAwait(false);
             if (!documentDiagnosticsToFix.TryGetValue(fixAllContext.Document, out var diagnostics))
             {

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/FixAll/FixAllState.FixMultipleDiagnosticProvider.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Threading;

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/FixAll/FixAllState.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -17,21 +19,21 @@ internal partial class FixAllState
 
         internal FixAllContext.DiagnosticProvider DiagnosticProvider { get; }
 
-        public FixAllProvider FixAllProvider { get; }
-        public string CodeActionEquivalenceKey { get; }
+        public FixAllProvider? FixAllProvider { get; }
+        public string? CodeActionEquivalenceKey { get; }
         public CodeFixProvider CodeFixProvider { get; }
         public ImmutableHashSet<string> DiagnosticIds { get; }
-        public Document Document { get; }
+        public Document? Document { get; }
         public Project Project { get; }
         public FixAllScope Scope { get; }
         public Solution Solution => this.Project.Solution;
 
         internal FixAllState(
-            FixAllProvider fixAllProvider,
+            FixAllProvider? fixAllProvider,
             Document document,
             CodeFixProvider codeFixProvider,
             FixAllScope scope,
-            string codeActionEquivalenceKey,
+            string? codeActionEquivalenceKey,
             IEnumerable<string> diagnosticIds,
             FixAllContext.DiagnosticProvider fixAllDiagnosticProvider)
             : this(fixAllProvider, document, document.Project, codeFixProvider, scope, codeActionEquivalenceKey, diagnosticIds, fixAllDiagnosticProvider)
@@ -43,11 +45,11 @@ internal partial class FixAllState
         }
 
         internal FixAllState(
-            FixAllProvider fixAllProvider,
+            FixAllProvider? fixAllProvider,
             Project project,
             CodeFixProvider codeFixProvider,
             FixAllScope scope,
-            string codeActionEquivalenceKey,
+            string? codeActionEquivalenceKey,
             IEnumerable<string> diagnosticIds,
             FixAllContext.DiagnosticProvider fixAllDiagnosticProvider)
             : this(fixAllProvider, null, project, codeFixProvider, scope, codeActionEquivalenceKey, diagnosticIds, fixAllDiagnosticProvider)
@@ -59,12 +61,12 @@ internal partial class FixAllState
         }
 
         private FixAllState(
-            FixAllProvider fixAllProvider,
-            Document document,
+            FixAllProvider? fixAllProvider,
+            Document? document,
             Project project,
             CodeFixProvider codeFixProvider,
             FixAllScope scope,
-            string codeActionEquivalenceKey,
+            string? codeActionEquivalenceKey,
             IEnumerable<string> diagnosticIds,
             FixAllContext.DiagnosticProvider fixAllDiagnosticProvider)
         {
@@ -91,7 +93,7 @@ internal partial class FixAllState
 
         internal bool IsFixMultiple => this.DiagnosticProvider is FixMultipleDiagnosticProvider;
 
-        public FixAllState WithScopeAndEquivalenceKey(FixAllScope scope, string codeActionEquivalenceKey)
+        public FixAllState WithScopeAndEquivalenceKey(FixAllScope scope, string? codeActionEquivalenceKey)
         {
             if (this.Scope == scope && this.CodeActionEquivalenceKey == codeActionEquivalenceKey)
             {

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/FixAllContextHelper.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Concurrent;
 using System.Collections.Immutable;
 using System.Linq;
@@ -17,7 +19,7 @@ internal static class FixAllContextHelper
     {
         public static async Task<ImmutableDictionary<Document, ImmutableArray<Diagnostic>>> GetDocumentDiagnosticsToFixAsync(
             FixAllContext fixAllContext,
-            IProgressTracker progressTrackerOpt)
+            IProgressTracker? progressTrackerOpt)
         {
             var cancellationToken = fixAllContext.CancellationToken;
 
@@ -86,14 +88,15 @@ internal static class FixAllContextHelper
             var treeToDocumentMap = await GetTreeToDocumentMapAsync(projects, cancellationToken).ConfigureAwait(false);
 
             var builder = ImmutableDictionary.CreateBuilder<Document, ImmutableArray<Diagnostic>>();
-            foreach (var documentAndDiagnostics in diagnostics.GroupBy(d => GetReportedDocument(d, treeToDocumentMap)))
+            foreach (var (document, diagnosticsForDocument) in diagnostics.GroupBy(d => GetReportedDocument(d, treeToDocumentMap)))
             {
+                if (document is null)
+                    continue;
+
                 cancellationToken.ThrowIfCancellationRequested();
-                var document = documentAndDiagnostics.Key;
                 if (!await document.IsGeneratedCodeAsync(cancellationToken).ConfigureAwait(false))
                 {
-                    var diagnosticsForDocument = documentAndDiagnostics.ToImmutableArray();
-                    builder.Add(document, diagnosticsForDocument);
+                    builder.Add(document, diagnosticsForDocument.ToImmutableArray());
                 }
             }
 
@@ -109,7 +112,7 @@ internal static class FixAllContextHelper
                 foreach (var document in project.Documents)
                 {
                     cancellationToken.ThrowIfCancellationRequested();
-                    var tree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
+                    var tree = await document.GetRequiredSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
                     builder.Add(tree, document);
                 }
             }
@@ -117,7 +120,7 @@ internal static class FixAllContextHelper
             return builder.ToImmutable();
         }
 
-        private static Document GetReportedDocument(Diagnostic diagnostic, ImmutableDictionary<SyntaxTree, Document> treeToDocumentsMap)
+        private static Document? GetReportedDocument(Diagnostic diagnostic, ImmutableDictionary<SyntaxTree, Document> treeToDocumentsMap)
         {
             var tree = diagnostic.Location.SourceTree;
             if (tree != null)
@@ -137,7 +140,7 @@ public static string GetDefaultFixAllTitle(FixAllContext fixAllContext)
         public static string GetDefaultFixAllTitle(
             FixAllScope fixAllScope,
             ImmutableHashSet<string> diagnosticIds,
-            Document triggerDocument,
+            Document? triggerDocument,
             Project triggerProject)
         {
             string diagnosticId;
@@ -156,7 +159,7 @@ public static string GetDefaultFixAllTitle(FixAllContext fixAllContext)
                     return string.Format(WorkspaceExtensionsResources.Fix_all_0, diagnosticId);
 
                 case FixAllScope.Document:
-                    return string.Format(WorkspaceExtensionsResources.Fix_all_0_in_1, diagnosticId, triggerDocument.Name);
+                    return string.Format(WorkspaceExtensionsResources.Fix_all_0_in_1, diagnosticId, triggerDocument!.Name);
 
                 case FixAllScope.Project:
                     return string.Format(WorkspaceExtensionsResources.Fix_all_0_in_1, diagnosticId, triggerProject.Name);

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/SyntaxEditorBasedCodeFixProvider.FixAllProvider.cs

@@ -2,10 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.CodeFixes
 {
@@ -24,7 +27,7 @@ internal sealed class SyntaxEditorBasedFixAllProvider : FixAllProvider
             public SyntaxEditorBasedFixAllProvider(SyntaxEditorBasedCodeFixProvider codeFixProvider)
                 => _codeFixProvider = codeFixProvider;
 
-            public sealed override async Task<CodeAction> GetFixAsync(FixAllContext fixAllContext)
+            public sealed override async Task<CodeAction?> GetFixAsync(FixAllContext fixAllContext)
             {
                 var documentsAndDiagnosticsToFixMap = await GetDocumentDiagnosticsToFixAsync(fixAllContext).ConfigureAwait(false);
                 return await GetFixAsync(documentsAndDiagnosticsToFixMap, fixAllContext).ConfigureAwait(false);
@@ -64,7 +67,7 @@ public sealed override async Task<CodeAction> GetFixAsync(FixAllContext fixAllCo
                     var updatedDocument = await task.ConfigureAwait(false);
                     currentSolution = currentSolution.WithDocumentSyntaxRoot(
                         updatedDocument.Id,
-                        await updatedDocument.GetSyntaxRootAsync(fixAllContext.CancellationToken).ConfigureAwait(false));
+                        await updatedDocument.GetRequiredSyntaxRootAsync(fixAllContext.CancellationToken).ConfigureAwait(false));
                 }
 
                 var title = FixAllContextHelper.GetDefaultFixAllTitle(fixAllContext);
@@ -74,7 +77,7 @@ public sealed override async Task<CodeAction> GetFixAsync(FixAllContext fixAllCo
             private async Task<Document> FixDocumentAsync(
                 Document document, ImmutableArray<Diagnostic> diagnostics, FixAllContext fixAllContext)
             {
-                var model = await document.GetSemanticModelAsync(fixAllContext.CancellationToken).ConfigureAwait(false);
+                var model = await document.GetRequiredSemanticModelAsync(fixAllContext.CancellationToken).ConfigureAwait(false);
 
                 // Ensure that diagnostics for this document are always in document location
                 // order.  This provides a consistent and deterministic order for fixers
@@ -82,7 +85,7 @@ public sealed override async Task<CodeAction> GetFixAsync(FixAllContext fixAllCo
                 // Also ensure that we do not pass in duplicates by invoking Distinct.
                 // See https://github.com/dotnet/roslyn/issues/31381, that seems to be causing duplicate diagnostics.
                 var filteredDiagnostics = diagnostics.Distinct()
-                                                     .WhereAsArray(d => _codeFixProvider.IncludeDiagnosticDuringFixAll(d, fixAllContext.Document, model, fixAllContext.CodeActionEquivalenceKey, fixAllContext.CancellationToken))
+                                                     .WhereAsArray(d => _codeFixProvider.IncludeDiagnosticDuringFixAll(d, document, model, fixAllContext.CodeActionEquivalenceKey, fixAllContext.CancellationToken))
                                                      .Sort((d1, d2) => d1.Location.SourceSpan.Start - d2.Location.SourceSpan.Start);
 
                 // PERF: Do not invoke FixAllAsync on the code fix provider if there are no diagnostics to be fixed.

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeFixes/SyntaxEditorBasedCodeFixProvider.cs

@@ -2,11 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.CodeFixes
 {
@@ -17,7 +20,7 @@ internal abstract partial class SyntaxEditorBasedCodeFixProvider : CodeFixProvid
         protected SyntaxEditorBasedCodeFixProvider(bool supportsFixAll = true)
             => _supportsFixAll = supportsFixAll;
 
-        public sealed override FixAllProvider GetFixAllProvider()
+        public sealed override FixAllProvider? GetFixAllProvider()
             => _supportsFixAll ? new SyntaxEditorBasedFixAllProvider(this) : null;
 
         protected Task<Document> FixAsync(
@@ -39,7 +42,7 @@ public sealed override FixAllProvider GetFixAllProvider()
             Func<SyntaxEditor, Task> editAsync,
             CancellationToken cancellationToken)
         {
-            var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
             var editor = new SyntaxEditor(root, document.Project.Solution.Workspace);
 
             await editAsync(editor).ConfigureAwait(false);
@@ -70,10 +73,10 @@ public sealed override FixAllProvider GetFixAllProvider()
         /// Only one of these three overloads needs to be overridden if you want to customize
         /// behavior.
         /// </summary>
-        protected virtual bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic, Document document, SemanticModel model, string equivalenceKey, CancellationToken cancellationToken)
+        protected virtual bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic, Document document, SemanticModel model, string? equivalenceKey, CancellationToken cancellationToken)
             => IncludeDiagnosticDuringFixAll(diagnostic, document, equivalenceKey, cancellationToken);
 
-        protected virtual bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic, Document document, string equivalenceKey, CancellationToken cancellationToken)
+        protected virtual bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic, Document document, string? equivalenceKey, CancellationToken cancellationToken)
             => IncludeDiagnosticDuringFixAll(diagnostic);
 
         /// <summary>