Add support for ExperimentalAttribute

Fixes #6759

Author: sharwell

src/PublicApiAnalyzers/Core/Analyzers/DeclarePublicApiAnalyzer.Impl.cs

@@ -589,11 +589,33 @@ private static bool UsesOblivious(ISymbol symbol)
 
             private ApiName GetApiName(ISymbol symbol)
             {
+                var experimentName = getExperimentName(symbol);
+
                 return new ApiName(
-                    getApiString(symbol, s_publicApiFormat),
-                    getApiString(symbol, s_publicApiFormatWithNullability));
+                    getApiString(_compilation, symbol, experimentName, s_publicApiFormat),
+                    getApiString(_compilation, symbol, experimentName, s_publicApiFormatWithNullability));
+
+                static string? getExperimentName(ISymbol symbol)
+                {
+                    for (var current = symbol; current is not null; current = current.ContainingSymbol)
+                    {
+                        foreach (var attribute in current.GetAttributes())
+                        {
+                            if (attribute.AttributeClass is { Name: "ExperimentalAttribute", ContainingSymbol: INamespaceSymbol { Name: nameof(System.Diagnostics.CodeAnalysis), ContainingNamespace: { Name: nameof(System.Diagnostics), ContainingNamespace: { Name: nameof(System), ContainingNamespace.IsGlobalNamespace: true } } } })
+                            {
+                                if (attribute.ConstructorArguments is not [{ Kind: TypedConstantKind.Primitive, Type.SpecialType: SpecialType.System_String, Value: string diagnosticId }])
+                                    return "???";
+
+                                return diagnosticId;
+
+                            }
+                        }
+                    }
+
+                    return null;
+                }
 
-                string getApiString(ISymbol symbol, SymbolDisplayFormat format)
+                static string getApiString(Compilation compilation, ISymbol symbol, string? experimentName, SymbolDisplayFormat format)
                 {
                     string publicApiName = symbol.ToDisplayString(format);
 
@@ -625,11 +647,16 @@ string getApiString(ISymbol symbol, SymbolDisplayFormat format)
                         return string.Empty;
                     }
 
-                    if (symbol.ContainingAssembly != null && !symbol.ContainingAssembly.Equals(_compilation.Assembly))
+                    if (symbol.ContainingAssembly != null && !symbol.ContainingAssembly.Equals(compilation.Assembly))
                     {
                         publicApiName += $" (forwarded, contained in {symbol.ContainingAssembly.Name})";
                     }
 
+                    if (experimentName != null)
+                    {
+                        publicApiName = "[" + experimentName + "]" + publicApiName;
+                    }
+
                     return publicApiName;
                 }
             }

src/PublicApiAnalyzers/UnitTests/DeclarePublicAPIAnalyzerTestsBase.cs

@@ -214,6 +214,11 @@ private async Task VerifyNet50CSharpAdditionalFileFixAsync(string source, string
             await VerifyAdditionalFileFixAsync(LanguageNames.CSharp, source, shippedApiText, oldUnshippedApiText, newUnshippedApiText, ReferenceAssemblies.Net.Net50);
         }
 
+        private async Task VerifyNet80CSharpAdditionalFileFixAsync(string source, string? shippedApiText, string? oldUnshippedApiText, string newUnshippedApiText)
+        {
+            await VerifyAdditionalFileFixAsync(LanguageNames.CSharp, source, shippedApiText, oldUnshippedApiText, newUnshippedApiText, AdditionalMetadataReferences.Net80);
+        }
+
         private async Task VerifyAdditionalFileFixAsync(string language, string source, string? shippedApiText, string? oldUnshippedApiText, string newUnshippedApiText,
             ReferenceAssemblies? referenceAssemblies = null)
         {
@@ -3219,6 +3224,77 @@ virtual R.PrintMembers(System.Text.StringBuilder! builder) -> bool
             await VerifyNet50CSharpAdditionalFileFixAsync(source, shippedText, unshippedText, fixedUnshippedText);
         }
 
+        [Fact]
+        [WorkItem(6759, "https://github.com/dotnet/roslyn-analyzers/issues/6759")]
+        public async Task TestExperimentalApiAsync()
+        {
+            var source = $$"""
+                using System.Diagnostics.CodeAnalysis;
+
+                [Experimental("ID1")]
+                {{EnabledModifierCSharp}} class {|{{AddNewApiId}}:{|{{AddNewApiId}}:C|}|}
+                {
+                }
+                """;
+
+            var shippedText = @"";
+            var unshippedText = @"";
+            var fixedUnshippedText = @"[ID1]C
+[ID1]C.C() -> void";
+
+            await VerifyNet80CSharpAdditionalFileFixAsync(source, shippedText, unshippedText, fixedUnshippedText);
+        }
+
+        [Theory]
+        [InlineData("")]
+        [InlineData("null")]
+        [InlineData("1")]
+        [InlineData("1, 2")]
+        [WorkItem(6759, "https://github.com/dotnet/roslyn-analyzers/issues/6759")]
+        public async Task TestExperimentalApiWithInvalidArgumentAsync(string invalidArgument)
+        {
+            var source = $$"""
+                using System.Diagnostics.CodeAnalysis;
+
+                [Experimental({{invalidArgument}})]
+                {{EnabledModifierCSharp}} class {|{{AddNewApiId}}:{|{{AddNewApiId}}:C|}|}
+                {
+                }
+                """;
+
+            var shippedText = @"";
+            var unshippedText = @"";
+            var fixedUnshippedText = @"[???]C
+[???]C.C() -> void";
+
+            var test = new CSharpCodeFixTest<DeclarePublicApiAnalyzer, DeclarePublicApiFix, XUnitVerifier>()
+            {
+                ReferenceAssemblies = AdditionalMetadataReferences.Net80,
+                CompilerDiagnostics = CompilerDiagnostics.None,
+                TestState =
+                {
+                    Sources = { source },
+                    AdditionalFiles =
+                    {
+                        (ShippedFileName, shippedText),
+                        (UnshippedFileName, unshippedText),
+                    },
+                },
+                FixedState =
+                {
+                    AdditionalFiles =
+                    {
+                        (ShippedFileName, shippedText),
+                        (UnshippedFileName, fixedUnshippedText),
+                    },
+                },
+            };
+
+            test.DisabledDiagnostics.AddRange(DisabledDiagnostics);
+
+            await test.RunAsync();
+        }
+
         #endregion
     }
 }