Allow null property values in Diagnostics

This is permitted by the runtime code in prior versions, so the annotations should signify that.

src/Analyzers/Core/Analyzers/PopulateSwitch/AbstractPopulateSwitchDiagnosticAnalyzer.cs

@@ -53,7 +53,7 @@ private void AnalyzeOperation(OperationAnalysisContext context)
                 !tree.OverlapsHiddenPosition(switchBlock.Span, context.CancellationToken))
             {
                 Debug.Assert(missingCases || missingDefaultCase);
-                var properties = ImmutableDictionary<string, string>.Empty
+                var properties = ImmutableDictionary<string, string?>.Empty
                     .Add(PopulateSwitchStatementHelpers.MissingCases, missingCases.ToString())
                     .Add(PopulateSwitchStatementHelpers.MissingDefaultCase, missingDefaultCase.ToString());
 

src/Analyzers/Core/CodeFixes/PopulateSwitch/AbstractPopulateSwitchCodeFixProvider.cs

@@ -58,8 +58,8 @@ public sealed override Task RegisterCodeFixesAsync(CodeFixContext context)
         {
             var diagnostic = context.Diagnostics.First();
             var properties = diagnostic.Properties;
-            var missingCases = bool.Parse(properties[PopulateSwitchStatementHelpers.MissingCases]);
-            var missingDefaultCase = bool.Parse(properties[PopulateSwitchStatementHelpers.MissingDefaultCase]);
+            var missingCases = bool.Parse(properties[PopulateSwitchStatementHelpers.MissingCases]!);
+            var missingDefaultCase = bool.Parse(properties[PopulateSwitchStatementHelpers.MissingDefaultCase]!);
 
             Debug.Assert(missingCases || missingDefaultCase);
 
@@ -137,8 +137,8 @@ private async Task FixOneDiagnosticAsync(
             bool addCases, bool addDefaultCase, bool onlyOneDiagnostic,
             CancellationToken cancellationToken)
         {
-            var hasMissingCases = bool.Parse(diagnostic.Properties[PopulateSwitchStatementHelpers.MissingCases]);
-            var hasMissingDefaultCase = bool.Parse(diagnostic.Properties[PopulateSwitchStatementHelpers.MissingDefaultCase]);
+            var hasMissingCases = bool.Parse(diagnostic.Properties[PopulateSwitchStatementHelpers.MissingCases]!);
+            var hasMissingDefaultCase = bool.Parse(diagnostic.Properties[PopulateSwitchStatementHelpers.MissingDefaultCase]!);
 
             var switchLocation = diagnostic.AdditionalLocations[0];
             var switchNode = switchLocation.FindNode(getInnermostNodeForTie: true, cancellationToken) as TSwitchSyntax;

src/Compilers/Core/Portable/CommandLine/SarifErrorLogger.cs

@@ -71,7 +71,7 @@ protected static string GetLevel(DiagnosticSeverity severity)
 
                 case DiagnosticSeverity.Hidden:
                 default:
-                    // hidden diagnostics are not reported on the command line and therefore not currently given to 
+                    // hidden diagnostics are not reported on the command line and therefore not currently given to
                     // the error logger. We could represent it with a custom property in the SARIF log if that changes.
                     Debug.Assert(false);
                     goto case DiagnosticSeverity.Warning;
@@ -124,7 +124,7 @@ protected static string GetUri(string path)
         {
             Debug.Assert(!string.IsNullOrEmpty(path));
 
-            // Note that in general, these "paths" are opaque strings to be 
+            // Note that in general, these "paths" are opaque strings to be
             // interpreted by resolvers (see SyntaxTree.FilePath documentation).
 
             // Common case: absolute path -> absolute URI

src/Compilers/Core/Portable/Diagnostic/Diagnostic.DiagnosticWithProgrammaticSuppression.cs

@@ -80,7 +80,7 @@ public override IReadOnlyList<Location> AdditionalLocations
                 get { return _originalUnsuppressedDiagnostic.AdditionalLocations; }
             }
 
-            public override ImmutableDictionary<string, string> Properties
+            public override ImmutableDictionary<string, string?> Properties
             {
                 get { return _originalUnsuppressedDiagnostic.Properties; }
             }

src/Compilers/Core/Portable/Diagnostic/Diagnostic.cs

@@ -58,7 +58,7 @@ public static Diagnostic Create(
         public static Diagnostic Create(
             DiagnosticDescriptor descriptor,
             Location? location,
-            ImmutableDictionary<string, string>? properties,
+            ImmutableDictionary<string, string?>? properties,
             params object?[]? messageArgs)
         {
             return Create(descriptor, location, null, properties, messageArgs);
@@ -106,7 +106,7 @@ public static Diagnostic Create(
             DiagnosticDescriptor descriptor,
             Location? location,
             IEnumerable<Location>? additionalLocations,
-            ImmutableDictionary<string, string>? properties,
+            ImmutableDictionary<string, string?>? properties,
             params object?[]? messageArgs)
         {
             return Create(descriptor, location, effectiveSeverity: descriptor.DefaultSeverity, additionalLocations, properties, messageArgs);
@@ -135,7 +135,7 @@ public static Diagnostic Create(
             Location? location,
             DiagnosticSeverity effectiveSeverity,
             IEnumerable<Location>? additionalLocations,
-            ImmutableDictionary<string, string>? properties,
+            ImmutableDictionary<string, string?>? properties,
             params object?[]? messageArgs)
         {
             if (descriptor == null)
@@ -197,7 +197,7 @@ public static Diagnostic Create(
             Location? location = null,
             IEnumerable<Location>? additionalLocations = null,
             IEnumerable<string>? customTags = null,
-            ImmutableDictionary<string, string>? properties = null)
+            ImmutableDictionary<string, string?>? properties = null)
         {
             return Create(id, category, message, severity, defaultSeverity, isEnabledByDefault, warningLevel, false,
                 title, description, helpLink, location, additionalLocations, customTags, properties);
@@ -248,7 +248,7 @@ public static Diagnostic Create(
             Location? location = null,
             IEnumerable<Location>? additionalLocations = null,
             IEnumerable<string>? customTags = null,
-            ImmutableDictionary<string, string>? properties = null)
+            ImmutableDictionary<string, string?>? properties = null)
         {
             if (id == null)
             {
@@ -398,8 +398,8 @@ public bool IsWarningAsError
         /// if there is no entry. This can be used to put diagnostic specific information you want 
         /// to pass around. for example, to corresponding fixer.
         /// </summary>
-        public virtual ImmutableDictionary<string, string> Properties
-            => ImmutableDictionary<string, string>.Empty;
+        public virtual ImmutableDictionary<string, string?> Properties
+            => ImmutableDictionary<string, string?>.Empty;
 
         string IFormattable.ToString(string? ignored, IFormatProvider? formatProvider)
         {

src/Compilers/Core/Portable/Diagnostic/Diagnostic_SimpleDiagnostic.cs

@@ -26,7 +26,7 @@ internal sealed class SimpleDiagnostic : Diagnostic
             private readonly Location _location;
             private readonly IReadOnlyList<Location> _additionalLocations;
             private readonly object?[] _messageArgs;
-            private readonly ImmutableDictionary<string, string> _properties;
+            private readonly ImmutableDictionary<string, string?> _properties;
             private readonly bool _isSuppressed;
 
             private SimpleDiagnostic(
@@ -36,7 +36,7 @@ private SimpleDiagnostic(
                 Location location,
                 IEnumerable<Location>? additionalLocations,
                 object?[]? messageArgs,
-                ImmutableDictionary<string, string>? properties,
+                ImmutableDictionary<string, string?>? properties,
                 bool isSuppressed)
             {
                 if ((warningLevel == 0 && severity != DiagnosticSeverity.Error) ||
@@ -51,7 +51,7 @@ private SimpleDiagnostic(
                 _location = location ?? Location.None;
                 _additionalLocations = additionalLocations?.ToImmutableArray() ?? SpecializedCollections.EmptyReadOnlyList<Location>();
                 _messageArgs = messageArgs ?? Array.Empty<object?>();
-                _properties = properties ?? ImmutableDictionary<string, string>.Empty;
+                _properties = properties ?? ImmutableDictionary<string, string?>.Empty;
                 _isSuppressed = isSuppressed;
             }
 
@@ -62,7 +62,7 @@ internal static SimpleDiagnostic Create(
                 Location location,
                 IEnumerable<Location>? additionalLocations,
                 object?[]? messageArgs,
-                ImmutableDictionary<string, string>? properties,
+                ImmutableDictionary<string, string?>? properties,
                 bool isSuppressed = false)
             {
                 return new SimpleDiagnostic(descriptor, severity, warningLevel, location, additionalLocations, messageArgs, properties, isSuppressed);
@@ -72,7 +72,7 @@ internal static SimpleDiagnostic Create(string id, LocalizableString title, stri
                                       DiagnosticSeverity severity, DiagnosticSeverity defaultSeverity,
                                       bool isEnabledByDefault, int warningLevel, Location location,
                                       IEnumerable<Location>? additionalLocations, IEnumerable<string>? customTags,
-                                      ImmutableDictionary<string, string>? properties, bool isSuppressed = false)
+                                      ImmutableDictionary<string, string?>? properties, bool isSuppressed = false)
             {
                 var descriptor = new DiagnosticDescriptor(id, title, message,
                      category, defaultSeverity, isEnabledByDefault, description, helpLink, customTags.ToImmutableArrayOrEmpty());
@@ -139,7 +139,7 @@ public override IReadOnlyList<Location> AdditionalLocations
                 get { return _additionalLocations; }
             }
 
-            public override ImmutableDictionary<string, string> Properties
+            public override ImmutableDictionary<string, string?> Properties
             {
                 get { return _properties; }
             }

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

@@ -78,7 +78,7 @@ public void WriteKey(string key)
             _pending = Pending.None;
         }
 
-        public void Write(string key, string value)
+        public void Write(string key, string? value)
         {
             WriteKey(key);
             Write(value);
@@ -96,7 +96,7 @@ public void Write(string key, bool value)
             Write(value);
         }
 
-        public void Write(string value)
+        public void Write(string? value)
         {
             WritePending();
             _output.Write('"');

src/Features/Core/Portable/Diagnostics/AnalyzerHelper.cs

@@ -240,7 +240,7 @@ static string GetLanguageSpecificId(string? language, string noLanguageId, strin
                 warningLevel: 0,
                 projectId: projectId,
                 customTags: ImmutableArray<string>.Empty,
-                properties: ImmutableDictionary<string, string>.Empty,
+                properties: ImmutableDictionary<string, string?>.Empty,
                 language: language);
         }
 

src/Workspaces/Core/Portable/Diagnostics/DiagnosticData.cs

@@ -33,7 +33,7 @@ internal sealed class DiagnosticData : IEquatable<DiagnosticData?>
         public readonly bool IsEnabledByDefault;
         public readonly int WarningLevel;
         public readonly IReadOnlyList<string> CustomTags;
-        public readonly ImmutableDictionary<string, string> Properties;
+        public readonly ImmutableDictionary<string, string?> Properties;
 
         public readonly ProjectId? ProjectId;
         public readonly DiagnosticDataLocation? DataLocation;
@@ -65,7 +65,7 @@ public DiagnosticData(
             bool isEnabledByDefault,
             int warningLevel,
             IReadOnlyList<string> customTags,
-            ImmutableDictionary<string, string> properties,
+            ImmutableDictionary<string, string?> properties,
             ProjectId? projectId,
             DiagnosticDataLocation? location = null,
             IReadOnlyCollection<DiagnosticDataLocation>? additionalLocations = null,
@@ -358,7 +358,7 @@ public static DiagnosticData Create(Diagnostic diagnostic, Document document)
             {
                 if (additionalProperties == null)
                 {
-                    additionalProperties = ImmutableDictionary.Create<string, string>();
+                    additionalProperties = ImmutableDictionary.Create<string, string?>();
                 }
 
                 additionalProperties = additionalProperties.Add(nameof(documentPropertiesService.DiagnosticsLspClientName), diagnosticsLspClientName);
@@ -380,7 +380,7 @@ private static DiagnosticData Create(
             OptionSet options,
             DiagnosticDataLocation? location,
             IReadOnlyCollection<DiagnosticDataLocation>? additionalLocations,
-            ImmutableDictionary<string, string>? additionalProperties)
+            ImmutableDictionary<string, string?>? additionalProperties)
         {
             return new DiagnosticData(
                 diagnostic.Id,
@@ -403,7 +403,7 @@ private static DiagnosticData Create(
                 isSuppressed: diagnostic.IsSuppressed);
         }
 
-        private static ImmutableDictionary<string, string>? GetAdditionalProperties(Document document, Diagnostic diagnostic)
+        private static ImmutableDictionary<string, string?>? GetAdditionalProperties(Document document, Diagnostic diagnostic)
         {
             var service = document.GetLanguageService<IDiagnosticPropertiesService>();
             return service?.GetAdditionalProperties(diagnostic);

src/Workspaces/Core/Portable/Diagnostics/DiagnosticDataSerializer.cs

@@ -323,11 +323,11 @@ private static IReadOnlyCollection<DiagnosticDataLocation> ReadAdditionalLocatio
             return result;
         }
 
-        private static ImmutableDictionary<string, string> GetProperties(ObjectReader reader, int count)
+        private static ImmutableDictionary<string, string?> GetProperties(ObjectReader reader, int count)
         {
             if (count > 0)
             {
-                var properties = ImmutableDictionary.CreateBuilder<string, string>();
+                var properties = ImmutableDictionary.CreateBuilder<string, string?>();
                 for (var i = 0; i < count; i++)
                 {
                     properties.Add(reader.ReadString(), reader.ReadString());
@@ -336,7 +336,7 @@ private static ImmutableDictionary<string, string> GetProperties(ObjectReader re
                 return properties.ToImmutable();
             }
 
-            return ImmutableDictionary<string, string>.Empty;
+            return ImmutableDictionary<string, string?>.Empty;
         }
 
         private static IReadOnlyList<string> GetCustomTags(ObjectReader reader, int count)