Merge pull request #163 from meziantou/polyfill/fix-duplicate-member-generation

Fix duplicate member generation when multiple IVT assemblies reference polyfill

Author: meziantou

Meziantou.Polyfill.SourceGenerator.Tests/UnitTest1.cs

@@ -85,6 +85,29 @@ public async Task InternalsVisibleTo_DoNotRegenerateExtensionMethods()
 
     }
 
+    [Fact]
+    public async Task InternalsVisibleTo_TwoReferencedAssemblies_DoNotCauseAmbiguity()
+    {
+        var assemblies = await NuGetHelpers.GetNuGetReferences("NETStandard.Library", "2.0.3", "build/");
+
+        // Generate two assemblies that both expose internals to "main"
+        var proj2Generation = GenerateFiles("""[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("main")]""", assemblyName: "proj2", assemblyLocations: assemblies);
+        Assert.Single(GetFileNames(proj2Generation.GeneratorResult), file => file is "T_System.Diagnostics.CodeAnalysis.StringSyntaxAttribute.g.cs");
+
+        var proj3Generation = GenerateFiles("""[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("main")]""", assemblyName: "proj3", assemblyLocations: assemblies);
+        Assert.Single(GetFileNames(proj3Generation.GeneratorResult), file => file is "T_System.Diagnostics.CodeAnalysis.StringSyntaxAttribute.g.cs");
+
+        var proj2Dll = Path.GetTempFileName() + ".dll";
+        var proj3Dll = Path.GetTempFileName() + ".dll";
+        await File.WriteAllBytesAsync(proj2Dll, proj2Generation.Assembly!);
+        await File.WriteAllBytesAsync(proj3Dll, proj3Generation.Assembly!);
+
+        // "main" references both assemblies. The generator must still produce types
+        // that would otherwise be ambiguous (CS0433) between proj2 and proj3.
+        var result = GenerateFiles("", assemblyName: "main", assemblyLocations: assemblies.Append(proj2Dll).Append(proj3Dll));
+        Assert.Single(GetFileNames(result.GeneratorResult), file => file is "T_System.Diagnostics.CodeAnalysis.StringSyntaxAttribute.g.cs");
+    }
+
     [Theory]
     [MemberData(nameof(GetConfigurations))]
     public async Task GeneratedCodeCompile(PackageReference[] packages, bool allowUnsafe)

Meziantou.Polyfill/Members.cs

@@ -13,16 +13,32 @@ private static bool IncludeMember(IncludeContext context, string memberDocumenta
             return false;
 
         var symbols = DocumentationCommentId.GetSymbolsForDeclarationId(memberDocumentationId, context.Compilation);
+        IAssemblySymbol? accessibleFromAssembly = null;
         foreach (var symbol in symbols)
         {
             if (ReferenceEquals(symbol.ContainingAssembly, context.Compilation.Assembly))
                 return false;
 
             // IsEmbeddedSymbol is a workaround for https://github.com/dotnet/roslyn/issues/79498
             if (context.Compilation.IsSymbolAccessibleWithin(symbol, context.Compilation.Assembly) && !IsEmbeddedSymbol(symbol))
-                return false;
+            {
+                if (accessibleFromAssembly is null)
+                {
+                    accessibleFromAssembly = symbol.ContainingAssembly;
+                }
+                else if (!ReferenceEquals(accessibleFromAssembly, symbol.ContainingAssembly))
+                {
+                    // The symbol is accessible from multiple assemblies, which would cause
+                    // ambiguity (e.g. CS0433). Generate a local copy so the compiler prefers
+                    // the current assembly's definition.
+                    return true;
+                }
+            }
         }
 
+        if (accessibleFromAssembly is not null)
+            return false;
+
         return true;
     }
 

Meziantou.Polyfill/Meziantou.Polyfill.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Meziantou.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
-    <Version>1.0.105</Version>
+    <Version>1.0.106</Version>
     <TransformOnBuild>true</TransformOnBuild>
     <RoslynVersion>4.3.1</RoslynVersion>