Add style option (and UI) for preferring file scoped namespaces

src/Analyzers/Core/Analyzers/AbstractBuiltInCodeStyleDiagnosticAnalyzer_Core.cs

@@ -50,13 +50,13 @@ protected static DiagnosticDescriptor CreateDescriptorWithId(
             string id,
             EnforceOnBuild enforceOnBuild,
             LocalizableString title,
-            LocalizableString messageFormat,
+            LocalizableString? messageFormat = null,
             bool isUnnecessary = false,
             bool isConfigurable = true,
             LocalizableString? description = null)
 #pragma warning disable RS0030 // Do not used banned APIs
             => new(
-                    id, title, messageFormat,
+                    id, title, messageFormat ?? title,
                     DiagnosticCategory.Style,
                     DiagnosticSeverity.Hidden,
                     isEnabledByDefault: true,

src/Analyzers/Core/Analyzers/EnforceOnBuildValues.cs

@@ -26,6 +26,8 @@ internal static class EnforceOnBuildValues
         public const EnforceOnBuild InvalidSuppressMessageAttribute = /*IDE0076*/ EnforceOnBuild.HighlyRecommended;
         public const EnforceOnBuild LegacyFormatSuppressMessageAttribute = /*IDE0077*/ EnforceOnBuild.HighlyRecommended;
         public const EnforceOnBuild RemoveConfusingSuppressionForIsExpression = /*IDE0080*/ EnforceOnBuild.HighlyRecommended;
+        public const EnforceOnBuild UseBlockScopedNamespace = /*IDE0160*/ EnforceOnBuild.HighlyRecommended;
+        public const EnforceOnBuild UseFileScopedNamespace = /*IDE0161*/ EnforceOnBuild.HighlyRecommended;
 
         /* EnforceOnBuild.Recommended */
         public const EnforceOnBuild UseThrowExpression = /*IDE0016*/ EnforceOnBuild.Recommended;

src/Analyzers/Core/Analyzers/IDEDiagnosticIds.cs

@@ -162,6 +162,9 @@ internal static class IDEDiagnosticIds
 
         public const string UseNullCheckOverTypeCheckDiagnosticId = "IDE0150";
 
+        public const string UseBlockScopedNamespaceDiagnosticId = "IDE0160";
+        public const string UseFileScopedNamespaceDiagnosticId = "IDE0161";
+
         // Analyzer error Ids
         public const string AnalyzerChangedId = "IDE1001";
         public const string AnalyzerDependencyConflictId = "IDE1002";

src/Analyzers/Core/CodeFixes/PredefinedCodeFixProviderNames.cs

@@ -17,6 +17,7 @@ internal static class PredefinedCodeFixProviderNames
         public const string ChangeToYield = nameof(ChangeToYield);
         public const string ConvertToAsync = nameof(ConvertToAsync);
         public const string ConvertToIterator = nameof(ConvertToIterator);
+        public const string ConvertNamespace = nameof(ConvertNamespace);
         public const string CorrectNextControlVariable = nameof(CorrectNextControlVariable);
         public const string ConvertTypeOfToNameOf = nameof(ConvertTypeOfToNameOf);
         public const string RemoveDocCommentNode = nameof(RemoveDocCommentNode);