Enable nullable reference types for the repo

Directory.Build.props

@@ -11,6 +11,9 @@
   <PropertyGroup>
     <LangVersion Condition="'$(Language)' == 'C#'">8</LangVersion>
     <LangVersion Condition="'$(Language)' == 'VB'">16</LangVersion>
+
+    <!-- TODO: Enable Nullable for test and non-shipping projects -->
+    <Nullable Condition="'$(Nullable)' == '' and '$(IsTestProject)' != 'true' and '$(NonShipping)' != 'true'">enable</Nullable>
   </PropertyGroup>
 
   <PropertyGroup>

src/MetaCompilation.Analyzers/Core/CodeFixProvider.cs

@@ -1,5 +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.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;

src/MetaCompilation.Analyzers/Core/DiagnosticAnalyzer.cs

@@ -1,5 +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.
 
+#nullable disable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;

src/Microsoft.CodeAnalysis.Analyzers/CSharp/CSharpImmutableObjectMethodAnalyzer.cs

@@ -50,15 +50,15 @@ public override void Initialize(AnalysisContext context)
 
             context.RegisterCompilationStartAction(compilationContext =>
             {
-                INamedTypeSymbol solutionSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(SolutionFullName);
-                INamedTypeSymbol projectSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(ProjectFullName);
-                INamedTypeSymbol documentSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(DocumentFullName);
-                INamedTypeSymbol syntaxNodeSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(SyntaxNodeFullName);
-                INamedTypeSymbol compilationSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(CompilationFullName);
+                INamedTypeSymbol? solutionSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(SolutionFullName);
+                INamedTypeSymbol? projectSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(ProjectFullName);
+                INamedTypeSymbol? documentSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(DocumentFullName);
+                INamedTypeSymbol? syntaxNodeSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(SyntaxNodeFullName);
+                INamedTypeSymbol? compilationSymbol = compilationContext.Compilation.GetOrCreateTypeByMetadataName(CompilationFullName);
 
-                ImmutableArray<INamedTypeSymbol> immutableSymbols = ImmutableArray.Create(solutionSymbol, projectSymbol, documentSymbol, syntaxNodeSymbol, compilationSymbol);
+                ImmutableArray<INamedTypeSymbol> immutableSymbols = ImmutableArray.CreateRange(new[] { solutionSymbol, projectSymbol, documentSymbol, syntaxNodeSymbol, compilationSymbol }.WhereNotNull());
                 //Only register our node action if we can find the symbols for our immutable types
-                if (immutableSymbols.Any(n => n == null))
+                if (immutableSymbols.IsEmpty)
                 {
                     return;
                 }

src/Microsoft.CodeAnalysis.Analyzers/CSharp/MetaAnalyzers/CSharpRegisterActionAnalyzer.cs

@@ -23,19 +23,19 @@ public class CSharpRegisterActionAnalyzer : RegisterActionAnalyzer<ClassDeclarat
             INamedTypeSymbol operationBlockStartAnalysisContext,
             INamedTypeSymbol symbolKind)
         {
-            INamedTypeSymbol csharpSyntaxKind = compilation.GetOrCreateTypeByMetadataName(CSharpSyntaxKindName);
-            INamedTypeSymbol basicSyntaxKind = compilation.GetOrCreateTypeByMetadataName(BasicSyntaxKindName);
+            INamedTypeSymbol? csharpSyntaxKind = compilation.GetOrCreateTypeByMetadataName(CSharpSyntaxKindName);
+            INamedTypeSymbol? basicSyntaxKind = compilation.GetOrCreateTypeByMetadataName(BasicSyntaxKindName);
             return new CSharpRegisterActionCodeBlockAnalyzer(csharpSyntaxKind, basicSyntaxKind, analysisContext, compilationStartAnalysisContext,
                 codeBlockStartAnalysisContext, operationBlockStartAnalysisContext, symbolKind);
         }
 
         private sealed class CSharpRegisterActionCodeBlockAnalyzer : RegisterActionCodeBlockAnalyzer
         {
-            private readonly ITypeSymbol _csharpSyntaxKind, _basicSyntaxKind;
+            private readonly ITypeSymbol? _csharpSyntaxKind, _basicSyntaxKind;
 
             public CSharpRegisterActionCodeBlockAnalyzer(
-                INamedTypeSymbol csharpSyntaxKind,
-                INamedTypeSymbol basicSyntaxKind,
+                INamedTypeSymbol? csharpSyntaxKind,
+                INamedTypeSymbol? basicSyntaxKind,
                 INamedTypeSymbol analysisContext,
                 INamedTypeSymbol compilationStartAnalysisContext,
                 INamedTypeSymbol codeBlockStartAnalysisContext,
@@ -51,7 +51,7 @@ private sealed class CSharpRegisterActionCodeBlockAnalyzer : RegisterActionCodeB
             protected override SyntaxKind ArgumentSyntaxKind => SyntaxKind.Argument;
             protected override SyntaxKind ParameterSyntaxKind => SyntaxKind.Parameter;
 
-            protected override IEnumerable<SyntaxNode> GetArgumentExpressions(InvocationExpressionSyntax invocation)
+            protected override IEnumerable<SyntaxNode>? GetArgumentExpressions(InvocationExpressionSyntax invocation)
             {
                 if (invocation.ArgumentList != null)
                 {
@@ -71,7 +71,7 @@ protected override SyntaxNode GetInvocationExpression(InvocationExpressionSyntax
                 return invocation.Expression;
             }
 
-            protected override SyntaxNode GetInvocationReceiver(InvocationExpressionSyntax invocation)
+            protected override SyntaxNode? GetInvocationReceiver(InvocationExpressionSyntax invocation)
             {
                 return (invocation.Expression as MemberAccessExpressionSyntax)?.Expression;
             }

src/Microsoft.CodeAnalysis.Analyzers/CSharp/MetaAnalyzers/CSharpReportDiagnosticAnalyzer.cs

@@ -24,7 +24,7 @@ public CSharpReportDiagnosticCompilationAnalyzer(ImmutableHashSet<INamedTypeSymb
             {
             }
 
-            protected override IEnumerable<SyntaxNode> GetArgumentExpressions(InvocationExpressionSyntax invocation)
+            protected override IEnumerable<SyntaxNode>? GetArgumentExpressions(InvocationExpressionSyntax invocation)
             {
                 if (invocation.ArgumentList != null)
                 {

src/Microsoft.CodeAnalysis.Analyzers/Core/FixAnalyzers/FixerWithFixAllAnalyzer.Fixer.cs

@@ -55,8 +55,13 @@ private static async Task<Document> AddMethodAsync(Document document, SyntaxNode
             var model = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
             var typeIsSealed = ((INamedTypeSymbol)model.GetDeclaredSymbol(classDecl)).IsSealed;
 
-            INamedTypeSymbol codeFixProviderSymbol = model.Compilation.GetOrCreateTypeByMetadataName(FixerWithFixAllAnalyzer.CodeFixProviderMetadataName);
-            IMethodSymbol getFixAllProviderMethod = codeFixProviderSymbol.GetMembers(FixerWithFixAllAnalyzer.GetFixAllProviderMethodName).OfType<IMethodSymbol>().First();
+            INamedTypeSymbol? codeFixProviderSymbol = model.Compilation.GetOrCreateTypeByMetadataName(FixerWithFixAllAnalyzer.CodeFixProviderMetadataName);
+            IMethodSymbol? getFixAllProviderMethod = codeFixProviderSymbol?.GetMembers(FixerWithFixAllAnalyzer.GetFixAllProviderMethodName).OfType<IMethodSymbol>().FirstOrDefault();
+            if (getFixAllProviderMethod == null)
+            {
+                return document;
+            }
+
             var returnStatement = generator.ReturnStatement(generator.MemberAccessExpression(
                 generator.IdentifierName("WellKnownFixAllProviders"), "BatchFixer"));
             var statements = new SyntaxNode[] { returnStatement };

src/Microsoft.CodeAnalysis.Analyzers/Core/FixAnalyzers/FixerWithFixAllAnalyzer.cs

@@ -86,37 +86,33 @@ private void CreateAnalyzerWithinCompilation(CompilationStartAnalysisContext con
         {
             context.CancellationToken.ThrowIfCancellationRequested();
 
-            INamedTypeSymbol codeFixProviderSymbol = context.Compilation.GetOrCreateTypeByMetadataName(CodeFixProviderMetadataName);
+            INamedTypeSymbol? codeFixProviderSymbol = context.Compilation.GetOrCreateTypeByMetadataName(CodeFixProviderMetadataName);
             if (codeFixProviderSymbol == null)
             {
                 return;
             }
 
-            IMethodSymbol getFixAllProviderMethod = codeFixProviderSymbol.GetMembers(GetFixAllProviderMethodName).OfType<IMethodSymbol>().FirstOrDefault();
+            IMethodSymbol? getFixAllProviderMethod = codeFixProviderSymbol.GetMembers(GetFixAllProviderMethodName).OfType<IMethodSymbol>().FirstOrDefault();
             if (getFixAllProviderMethod == null)
             {
                 return;
             }
 
-            INamedTypeSymbol codeActionSymbol = context.Compilation.GetOrCreateTypeByMetadataName(CodeActionMetadataName);
+            INamedTypeSymbol? codeActionSymbol = context.Compilation.GetOrCreateTypeByMetadataName(CodeActionMetadataName);
             if (codeActionSymbol == null)
             {
                 return;
             }
 
-            IEnumerable<IMethodSymbol> createSymbols = codeActionSymbol.GetMembers(CreateMethodName).OfType<IMethodSymbol>();
-            if (createSymbols == null)
-            {
-                return;
-            }
-
-            IPropertySymbol equivalenceKeyProperty = codeActionSymbol.GetMembers(EquivalenceKeyPropertyName).OfType<IPropertySymbol>().FirstOrDefault();
+            IPropertySymbol? equivalenceKeyProperty = codeActionSymbol.GetMembers(EquivalenceKeyPropertyName).OfType<IPropertySymbol>().FirstOrDefault();
             if (equivalenceKeyProperty == null)
             {
                 return;
             }
 
-            CompilationAnalyzer compilationAnalyzer = new CompilationAnalyzer(codeFixProviderSymbol, codeActionSymbol, context.Compilation.Assembly, createMethods: ImmutableHashSet.CreateRange(createSymbols));
+            var createMethods = codeActionSymbol.GetMembers(CreateMethodName).OfType<IMethodSymbol>().ToImmutableHashSet();
+
+            CompilationAnalyzer compilationAnalyzer = new CompilationAnalyzer(codeFixProviderSymbol, codeActionSymbol, context.Compilation.Assembly, createMethods);
 
             context.RegisterSymbolAction(compilationAnalyzer.AnalyzeNamedTypeSymbol, SymbolKind.NamedType);
             context.RegisterOperationBlockStartAction(compilationAnalyzer.OperationBlockStart);

src/Microsoft.CodeAnalysis.Analyzers/Core/MetaAnalyzers/ConfigureGeneratedCodeAnalysisAnalyzer.cs

@@ -39,7 +39,7 @@ public override void Initialize(AnalysisContext context)
         }
 
         [SuppressMessage("AnalyzerPerformance", "RS1012:Start action has no registered actions.", Justification = "Method returns an analyzer that is registered by the caller.")]
-        protected override DiagnosticAnalyzerSymbolAnalyzer GetDiagnosticAnalyzerSymbolAnalyzer(CompilationStartAnalysisContext compilationContext, INamedTypeSymbol diagnosticAnalyzer, INamedTypeSymbol diagnosticAnalyzerAttribute)
+        protected override DiagnosticAnalyzerSymbolAnalyzer? GetDiagnosticAnalyzerSymbolAnalyzer(CompilationStartAnalysisContext compilationContext, INamedTypeSymbol diagnosticAnalyzer, INamedTypeSymbol diagnosticAnalyzerAttribute)
         {
             var compilation = compilationContext.Compilation;
 
@@ -62,7 +62,7 @@ protected override DiagnosticAnalyzerSymbolAnalyzer GetDiagnosticAnalyzerSymbolA
                     return;
                 }
 
-                IParameterSymbol analysisContextParameter = null;
+                IParameterSymbol? analysisContextParameter = null;
                 foreach (var parameter in method.Parameters)
                 {
                     if (!Equals(parameter.Type, analysisContext))

src/Microsoft.CodeAnalysis.Analyzers/Core/MetaAnalyzers/DiagnosticAnalyzerAPIUsageAnalyzer.cs

@@ -63,7 +63,7 @@ public override void Initialize(AnalysisContext context)
                     return;
                 }
 
-                INamedTypeSymbol diagnosticAnalyzer = compilationStartContext.Compilation.GetOrCreateTypeByMetadataName(DiagnosticAnalyzerCorrectnessAnalyzer.DiagnosticAnalyzerTypeFullName);
+                INamedTypeSymbol? diagnosticAnalyzer = compilationStartContext.Compilation.GetOrCreateTypeByMetadataName(DiagnosticAnalyzerCorrectnessAnalyzer.DiagnosticAnalyzerTypeFullName);
                 if (diagnosticAnalyzer == null)
                 {
                     // Does not contain any diagnostic analyzers.

src/Microsoft.CodeAnalysis.Analyzers/Core/MetaAnalyzers/DiagnosticAnalyzerAttributeAnalyzer.cs

@@ -63,9 +63,9 @@ private sealed class AttributeAnalyzer : DiagnosticAnalyzerSymbolAnalyzer
             private const string CSharpCompilationFullName = @"Microsoft.CodeAnalysis.CSharp.CSharpCompilation";
             private const string BasicCompilationFullName = @"Microsoft.CodeAnalysis.VisualBasic.VisualBasicCompilation";
 
-            private readonly INamedTypeSymbol _attributeUsageAttribute;
+            private readonly INamedTypeSymbol? _attributeUsageAttribute;
 
-            public AttributeAnalyzer(INamedTypeSymbol diagnosticAnalyzer, INamedTypeSymbol diagnosticAnalyzerAttribute, INamedTypeSymbol attributeUsageAttribute)
+            public AttributeAnalyzer(INamedTypeSymbol diagnosticAnalyzer, INamedTypeSymbol diagnosticAnalyzerAttribute, INamedTypeSymbol? attributeUsageAttribute)
                 : base(diagnosticAnalyzer, diagnosticAnalyzerAttribute)
             {
                 _attributeUsageAttribute = attributeUsageAttribute;
@@ -83,7 +83,7 @@ protected override void AnalyzeDiagnosticAnalyzer(SymbolAnalysisContext symbolCo
                 // 2) AddLanguageSupportToAnalyzerRule: For analyzer supporting only one of C# or VB languages, detect if it can support the other language.
 
                 var hasAttribute = false;
-                SyntaxNode attributeSyntax = null;
+                SyntaxNode? attributeSyntax = null;
                 bool supportsCSharp = false;
                 bool supportsVB = false;
 
@@ -133,11 +133,11 @@ protected override void AnalyzeDiagnosticAnalyzer(SymbolAnalysisContext symbolCo
                     // then the analyzer is pretty likely a language-agnostic analyzer.
                     Compilation compilation = symbolContext.Compilation;
                     string compilationTypeNameToCheck = supportsCSharp ? CSharpCompilationFullName : BasicCompilationFullName;
-                    INamedTypeSymbol compilationType = compilation.GetOrCreateTypeByMetadataName(compilationTypeNameToCheck);
+                    INamedTypeSymbol? compilationType = compilation.GetOrCreateTypeByMetadataName(compilationTypeNameToCheck);
                     if (compilationType == null)
                     {
                         string missingLanguage = supportsCSharp ? LanguageNames.VisualBasic : LanguageNames.CSharp;
-                        Diagnostic diagnostic = Diagnostic.Create(AddLanguageSupportToAnalyzerRule, attributeSyntax.GetLocation(), namedType.Name, missingLanguage);
+                        Diagnostic diagnostic = Diagnostic.Create(AddLanguageSupportToAnalyzerRule, attributeSyntax!.GetLocation(), namedType.Name, missingLanguage);
                         symbolContext.ReportDiagnostic(diagnostic);
                     }
                 }

src/Microsoft.CodeAnalysis.Analyzers/Core/MetaAnalyzers/DiagnosticAnalyzerCorrectnessAnalyzer.DiagnosticAnalyzerSymbolAnalyzer.cs

@@ -35,7 +35,7 @@ internal void AnalyzeSymbol(SymbolAnalysisContext symbolContext)
 
             protected abstract void AnalyzeDiagnosticAnalyzer(SymbolAnalysisContext symbolContext);
 
-            protected bool HasDiagnosticAnalyzerAttribute(INamedTypeSymbol namedType, INamedTypeSymbol attributeUsageAttribute)
+            protected bool HasDiagnosticAnalyzerAttribute(INamedTypeSymbol namedType, INamedTypeSymbol? attributeUsageAttribute)
             {
                 foreach (AttributeData attribute in namedType.GetApplicableAttributes(attributeUsageAttribute))
                 {

src/Microsoft.CodeAnalysis.Analyzers/Core/MetaAnalyzers/DiagnosticAnalyzerCorrectnessAnalyzer.cs

@@ -54,23 +54,23 @@ public override void Initialize(AnalysisContext context)
 
             context.RegisterCompilationStartAction(compilationContext =>
             {
-                INamedTypeSymbol diagnosticAnalyzer = compilationContext.Compilation.GetOrCreateTypeByMetadataName(DiagnosticAnalyzerTypeFullName);
-                INamedTypeSymbol diagnosticAnalyzerAttribute = compilationContext.Compilation.GetOrCreateTypeByMetadataName(DiagnosticAnalyzerAttributeFullName);
+                INamedTypeSymbol? diagnosticAnalyzer = compilationContext.Compilation.GetOrCreateTypeByMetadataName(DiagnosticAnalyzerTypeFullName);
+                INamedTypeSymbol? diagnosticAnalyzerAttribute = compilationContext.Compilation.GetOrCreateTypeByMetadataName(DiagnosticAnalyzerAttributeFullName);
 
                 if (diagnosticAnalyzer == null || diagnosticAnalyzerAttribute == null)
                 {
                     // We don't need to check assemblies unless they're referencing Microsoft.CodeAnalysis which defines DiagnosticAnalyzer.
                     return;
                 }
 
-                DiagnosticAnalyzerSymbolAnalyzer analyzer = GetDiagnosticAnalyzerSymbolAnalyzer(compilationContext, diagnosticAnalyzer, diagnosticAnalyzerAttribute);
+                DiagnosticAnalyzerSymbolAnalyzer? analyzer = GetDiagnosticAnalyzerSymbolAnalyzer(compilationContext, diagnosticAnalyzer, diagnosticAnalyzerAttribute);
                 if (analyzer != null)
                 {
                     compilationContext.RegisterSymbolAction(c => analyzer.AnalyzeSymbol(c), SymbolKind.NamedType);
                 }
             });
         }
 
-        protected abstract DiagnosticAnalyzerSymbolAnalyzer GetDiagnosticAnalyzerSymbolAnalyzer(CompilationStartAnalysisContext compilationContext, INamedTypeSymbol diagnosticAnalyzer, INamedTypeSymbol diagnosticAnalyzerAttribute);
+        protected abstract DiagnosticAnalyzerSymbolAnalyzer? GetDiagnosticAnalyzerSymbolAnalyzer(CompilationStartAnalysisContext compilationContext, INamedTypeSymbol diagnosticAnalyzer, INamedTypeSymbol diagnosticAnalyzerAttribute);
     }
 }