Add support for packing reference assemblies

Co-authored-by: kzu <169707+kzu@users.noreply.github.com>

Author: Copilot

src/NuGetizer.Tasks/NuGetizer.Inference.targets

@@ -36,6 +36,9 @@ Copyright (c) .NET Foundation. All rights reserved.
     <!-- Whether to include @(DebugSymbolsProjectOutputGroupOutput) items in the package -->
     <PackSymbols Condition="'$(PackSymbols)' == '' and '$(PackBuildOutput)' == 'true'">true</PackSymbols>
 
+    <!-- Whether to include the reference assembly ($(TargetRefPath)) in the package when ProduceReferenceAssembly=true -->
+    <PackRefAssembly Condition="'$(PackRefAssembly)' == '' and '$(PackBuildOutput)' == 'true' and '$(ProduceReferenceAssembly)' == 'true'">true</PackRefAssembly>
+
     <!-- Whether to include framework references (%(ReferencePath.ResolvedFrom)' == '{TargetFrameworkDirectory}') in the package -->
     <PackFrameworkReferences Condition="'$(PackFrameworkReferences)' == '' and '$(PackDependencies)' == 'false'">false</PackFrameworkReferences>
     <!-- Only default to true if the project isn't a nuget packaging project itself and its primary output is lib. -->
@@ -402,6 +405,14 @@ Copyright (c) .NET Foundation. All rights reserved.
       <_InferredPackageFile Include="@(_InferredProjectOutput -> Distinct())" />
     </ItemGroup>
 
+    <ItemGroup Label="Reference Assembly Inference" Condition="'$(PackRefAssembly)' == 'true' and '$(PackAsPublish)' != 'true' and '$(TargetRefPath)' != ''">
+      <!-- Include the reference assembly in the ref folder when ProduceReferenceAssembly=true -->
+      <_InferredPackageFile Include="$(TargetRefPath)">
+        <PackFolder>Ref</PackFolder>
+        <FrameworkSpecific>true</FrameworkSpecific>
+      </_InferredPackageFile>
+    </ItemGroup>
+
     <ItemGroup Label="SatelliteDll Resources from Dependencies" Condition="'$(PackBuildOutput)' == 'true' and '$(PackAsPublish)' != 'true'">
       <!-- Include transitive resources if their NuGetPackageId has PrivateAssets=all and Pack!=false only. -->
       <_InferredPackageFile Include="@(ResourceCopyLocalItems)"

src/NuGetizer.Tasks/NuGetizer.props

@@ -134,6 +134,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     </PackFolderKind>
     <PackFolderKind Include="Ref">
       <PackageFolder>ref</PackageFolder>
+      <FrameworkSpecific>true</FrameworkSpecific>
     </PackFolderKind>
     <PackFolderKind Include="Analyzer;Analyzers">
       <PackageFolder>analyzers</PackageFolder>

src/NuGetizer.Tests/InlineProjectTests.cs

@@ -1097,5 +1097,148 @@ public void when_dependency_is_development_dependency_then_can_explicitly_pack_i
                 Assert.Equal("ThisAssembly.Constants", manifest.Metadata.DependencyGroups.First().Packages.First().Id);
             }
         }
+
+        [Fact]
+        public void when_produce_reference_assembly_then_includes_ref_assembly()
+        {
+            var result = Builder.BuildProject(
+                """
+                <Project Sdk="Microsoft.NET.Sdk">
+                  <PropertyGroup>
+                    <TargetFramework>net8.0</TargetFramework>
+                    <ProduceReferenceAssembly>true</ProduceReferenceAssembly>
+                  </PropertyGroup>
+                </Project>
+                """, output: output);
+
+            result.AssertSuccess(output);
+
+            // Should have the main assembly in lib
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                Extension = ".dll",
+                PackFolder = PackFolderKind.Lib
+            }));
+
+            // Should also have the reference assembly in ref
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                Extension = ".dll",
+                PackFolder = PackFolderKind.Ref
+            }));
+        }
+
+        [Fact]
+        public void when_produce_reference_assembly_false_then_does_not_include_ref_assembly()
+        {
+            var result = Builder.BuildProject(
+                """
+                <Project Sdk="Microsoft.NET.Sdk">
+                  <PropertyGroup>
+                    <TargetFramework>net8.0</TargetFramework>
+                    <ProduceReferenceAssembly>false</ProduceReferenceAssembly>
+                  </PropertyGroup>
+                </Project>
+                """, output: output);
+
+            result.AssertSuccess(output);
+
+            // Should have the main assembly in lib
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                Extension = ".dll",
+                PackFolder = PackFolderKind.Lib
+            }));
+
+            // Should NOT have a reference assembly in ref
+            Assert.DoesNotContain(result.Items, item => item.Matches(new
+            {
+                PackFolder = PackFolderKind.Ref
+            }));
+        }
+
+        [Fact]
+        public void when_produce_reference_assembly_but_pack_build_output_false_then_does_not_include_ref_assembly()
+        {
+            var result = Builder.BuildProject(
+                """
+                <Project Sdk="Microsoft.NET.Sdk">
+                  <PropertyGroup>
+                    <TargetFramework>net8.0</TargetFramework>
+                    <ProduceReferenceAssembly>true</ProduceReferenceAssembly>
+                    <PackBuildOutput>false</PackBuildOutput>
+                  </PropertyGroup>
+                </Project>
+                """, output: output);
+
+            result.AssertSuccess(output);
+
+            // Should NOT have the main assembly in lib
+            Assert.DoesNotContain(result.Items, item => item.Matches(new
+            {
+                Extension = ".dll",
+                PackFolder = PackFolderKind.Lib
+            }));
+
+            // Should NOT have a reference assembly in ref either
+            Assert.DoesNotContain(result.Items, item => item.Matches(new
+            {
+                PackFolder = PackFolderKind.Ref
+            }));
+        }
+
+        [Fact]
+        public void when_produce_reference_assembly_can_opt_out_with_pack_ref_assembly_false()
+        {
+            var result = Builder.BuildProject(
+                """
+                <Project Sdk="Microsoft.NET.Sdk">
+                  <PropertyGroup>
+                    <TargetFramework>net8.0</TargetFramework>
+                    <ProduceReferenceAssembly>true</ProduceReferenceAssembly>
+                    <PackRefAssembly>false</PackRefAssembly>
+                  </PropertyGroup>
+                </Project>
+                """, output: output);
+
+            result.AssertSuccess(output);
+
+            // Should have the main assembly in lib
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                Extension = ".dll",
+                PackFolder = PackFolderKind.Lib
+            }));
+
+            // Should NOT have a reference assembly in ref
+            Assert.DoesNotContain(result.Items, item => item.Matches(new
+            {
+                PackFolder = PackFolderKind.Ref
+            }));
+        }
+
+        [Fact]
+        public void when_produce_reference_assembly_then_ref_assembly_is_framework_specific()
+        {
+            var result = Builder.BuildProject(
+                """
+                <Project Sdk="Microsoft.NET.Sdk">
+                  <PropertyGroup>
+                    <TargetFramework>net8.0</TargetFramework>
+                    <ProduceReferenceAssembly>true</ProduceReferenceAssembly>
+                    <IsPackable>true</IsPackable>
+                  </PropertyGroup>
+                </Project>
+                """, output: output);
+
+            result.AssertSuccess(output);
+
+            // The ref assembly should have a package path that includes the TFM
+            Assert.Contains(result.Items, item => item.Matches(new
+            {
+                PackFolder = PackFolderKind.Ref,
+                PackagePath = "ref/net8.0/scenario.dll"
+            }));
+        }
     }
 }