From e9747d34f128be2cafdcaa26888bcfd8e739ac2b Mon Sep 17 00:00:00 2001
From: TJ Cowen <TJ.Cowen@D2L.com>
Date: Wed, 8 Nov 2023 13:14:37 -0500
Subject: [PATCH] Allow OnlyVisibleToType on interfaces.

---
 src/D2L.CodeStyle.Analyzers/Diagnostics.cs    |  9 ++++
 .../Language/OnlyVisibleToAnalyzer.cs         | 45 ++++++++++++++++++-
 .../Contract/OnlyVisibleToTypeAttribute.cs    |  2 +-
 .../Specs/OnlyVisibleToAnalyzer.cs            | 32 ++++++++++++-
 4 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/src/D2L.CodeStyle.Analyzers/Diagnostics.cs b/src/D2L.CodeStyle.Analyzers/Diagnostics.cs
index 0b3a3ffa..f923e444 100644
--- a/src/D2L.CodeStyle.Analyzers/Diagnostics.cs
+++ b/src/D2L.CodeStyle.Analyzers/Diagnostics.cs
@@ -766,5 +766,14 @@ public static class Diagnostics {
 			defaultSeverity: DiagnosticSeverity.Error,
 			isEnabledByDefault: true
 		);
+
+		public static readonly DiagnosticDescriptor TypeNotVisibleToCaller = new DiagnosticDescriptor(
+			id: "D2L0103",
+			title: "Type is not visible to caller",
+			messageFormat: "The type '{0}' has restricted its visibility to an explicit set of callers",
+			category: "Correctness",
+			defaultSeverity: DiagnosticSeverity.Error,
+			isEnabledByDefault: true
+		);
 	}
 }
diff --git a/src/D2L.CodeStyle.Analyzers/Language/OnlyVisibleToAnalyzer.cs b/src/D2L.CodeStyle.Analyzers/Language/OnlyVisibleToAnalyzer.cs
index 8748c47f..4ff34e16 100644
--- a/src/D2L.CodeStyle.Analyzers/Language/OnlyVisibleToAnalyzer.cs
+++ b/src/D2L.CodeStyle.Analyzers/Language/OnlyVisibleToAnalyzer.cs
@@ -1,5 +1,7 @@
 using System.Collections.Immutable;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Operations;
 
@@ -9,7 +11,8 @@ namespace D2L.CodeStyle.Analyzers.Language {
 	public sealed partial class OnlyVisibleToAnalyzer : DiagnosticAnalyzer {
 
 		public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(
-			Diagnostics.MemberNotVisibleToCaller
+			Diagnostics.MemberNotVisibleToCaller,
+			Diagnostics.TypeNotVisibleToCaller
 		);
 
 		public override void Initialize( AnalysisContext context ) {
@@ -60,6 +63,46 @@ public static void OnCompilationStart( CompilationStartAnalysisContext context )
 				},
 				OperationKind.PropertyReference
 			);
+
+			context.RegisterSyntaxNodeAction(
+				context => {
+					AnalyzeTypeUsage( context, (IdentifierNameSyntax)context.Node, model );
+				},
+				SyntaxKind.IdentifierName
+			);
+		}
+
+		private static void AnalyzeTypeUsage(
+			SyntaxNodeAnalysisContext context,
+			IdentifierNameSyntax syntax,
+			in Model model
+		) {
+			// If there is no caller, we have nothing to check
+			INamedTypeSymbol? caller = context.ContainingSymbol?.ContainingType;
+			if( caller == null ) {
+				return;
+			}
+
+			// If the identifier itself is not for an interface, we have nothing to check
+			if( context.SemanticModel.GetSymbolInfo( syntax ).Symbol is not INamedTypeSymbol symbol
+				|| symbol.TypeKind != TypeKind.Interface ) {
+				return;
+			}
+
+			// Perform the visibility check
+			if( model.IsVisibleTo( caller, symbol ) ) {
+				return;
+			}
+
+			Diagnostic diagnostic = Diagnostic.Create(
+				Diagnostics.TypeNotVisibleToCaller,
+				syntax.GetLocation(),
+				messageArgs: new[] {
+					symbol.Name
+				}
+			);
+
+			context.ReportDiagnostic( diagnostic );
 		}
 
 		private static void AnalyzeMemberUsage(
diff --git a/src/D2L.CodeStyle.Annotations/Contract/OnlyVisibleToTypeAttribute.cs b/src/D2L.CodeStyle.Annotations/Contract/OnlyVisibleToTypeAttribute.cs
index 8a752ff5..cb8b08ab 100644
--- a/src/D2L.CodeStyle.Annotations/Contract/OnlyVisibleToTypeAttribute.cs
+++ b/src/D2L.CodeStyle.Annotations/Contract/OnlyVisibleToTypeAttribute.cs
@@ -3,7 +3,7 @@
 namespace D2L.CodeStyle.Annotations.Contract {
 
 	[AttributeUsage(
-		validOn: AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property,
+		validOn: AttributeTargets.Constructor | AttributeTargets.Interface | AttributeTargets.Method | AttributeTargets.Property,
 		AllowMultiple = true,
 		Inherited = false
 	)]
diff --git a/tests/D2L.CodeStyle.Analyzers.Test/Specs/OnlyVisibleToAnalyzer.cs b/tests/D2L.CodeStyle.Analyzers.Test/Specs/OnlyVisibleToAnalyzer.cs
index 68f63426..f70e4cd1 100644
--- a/tests/D2L.CodeStyle.Analyzers.Test/Specs/OnlyVisibleToAnalyzer.cs
+++ b/tests/D2L.CodeStyle.Analyzers.Test/Specs/OnlyVisibleToAnalyzer.cs
@@ -9,7 +9,7 @@
 namespace D2L.CodeStyle.Annotations.Contract {
 
 	[AttributeUsage(
-		validOn: AttributeTargets.Method | AttributeTargets.Property,
+		validOn: AttributeTargets.Interface | AttributeTargets.Method | AttributeTargets.Property,
 		AllowMultiple = true,
 		Inherited = false
 	)]
@@ -84,7 +84,7 @@ public static int RestrictedPropertySetter { set { } }
 
 namespace TestCases {
 
-	public static class AllowedCaller {
+	public static partial class AllowedCaller {
 
 		public const string MetadataName = "TestCases.AllowedCaller";
 
@@ -206,6 +206,34 @@ public static void Test() {
 
 // ===============================================================================
 
+namespace Targets {
+	[OnlyVisibleToType( TestCases.AllowedCaller.MetadataName, "OnlyVisibleToAnalyzer" )]
+	public interface ITypeRestrictedInterface { }
+	public interface ITypeUnrestrictedInterface { }
+}
+
+namespace TestCases {
+	public static partial class AllowedCaller {
+		public static void UnrestrictedInterface() {
+			ITypeUnrestrictedInterface @interface = null;
+		}
+		public static void RestrictedInterface() {
+			ITypeRestrictedInterface @interface = null;
+		}
+	}
+
+	public static partial class DisallowedCaller {
+		public static void UnrestrictedInterface() {
+			ITypeUnrestrictedInterface @interface = null;
+		}
+		public static void RestrictedInterface() {
+			/* TypeNotVisibleToCaller(ITypeRestrictedInterface) */ ITypeRestrictedInterface /**/ @interface = null;
+		}
+	}
+}
+
+// ===============================================================================
+
 namespace Targets {
 
 	public static class UnknownTargetTypes {