Update generator to add sbrp attribute

Author: ellahathaway

src/packageSourceGenerator/PackageSourceGenerator.proj

@@ -79,6 +79,7 @@
                             GenerateReferencePackageSource;
                             GenerateTextOnlyPackageSource;
                             GeneratePackageProject;
+                            AddSbrpAttribute;
                             RewriteNuspec;
                             EndGeneratePackageSource;
                             InvokePackageDependencies" />
@@ -285,6 +286,27 @@
              Importance="high" />
   </Target>
 
+  <!-- Add SBRP attribute to CSharp file and copy to target directory. -->
+  <ItemGroup>
+    <PackageCSharpFiles Include="$(PackageTargetDirectory)**/*.cs" />
+  </ItemGroup>
+
+  <UsingTask TaskName="AddSbrpAttribute" AssemblyFile="$(PackageSourceGeneratorTaskAssembly)" />
+  <Target Name="AddSbrpAttribute"
+          Condition="'@(PackageCompileItem)' != '' or '$(PackageType)' == 'text'">
+
+    <PropertyGroup>
+      <PackageCSharpTargetPath>%(PackageCSharpFiles.Identity)</PackageCSharpTargetPath>
+    </PropertyGroup>
+
+    <AddSbrpAttribute CSharpPath="$(PackageCSharpTargetPath)"
+                      TargetPath="$(PackageCSharpTargetPath)" />
+
+    <Message Text="$(MSBuildProjectName) -> $(PackageProjectTargetPath)"
+             Importance="high" />
+
+  </Target>
+
   <!-- Rewrite nuspec and copy to target directory. -->
   <UsingTask TaskName="RewriteNuspec" AssemblyFile="$(PackageSourceGeneratorTaskAssembly)" />
   <Target Name="RewriteNuspec"

src/packageSourceGenerator/PackageSourceGeneratorTask/AddSbrpAttribute.cs

@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.IO;
+using System.Text.RegularExpressions;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+namespace Microsoft.DotNet.SourceBuild.Tasks
+{
+    public partial class AddSbrpAttribute : Task
+    {
+
+        [Required]
+        public string? CSharpPath { get; set; }
+
+        [Required]
+        public string? TargetPath { get; set; }
+
+        public override bool Execute()
+        {
+            string specContent = File.ReadAllText(CSharpPath!);
+
+            Match versionMatch = GetVersionRegex().Match(specContent);
+
+            if (versionMatch.Success)
+            {
+                string version = versionMatch.Groups["version"].Value;
+
+                if (!GetSbrpAttributeRegex().IsMatch(specContent))
+                {
+                    string sbrpAttribute = $"[assembly: AssemblyInformationalVersion(\"{version} originated from source-build-reference-packages\")]";
+
+                    specContent = GetVersionRegex().Replace(specContent, $"{versionMatch.Value}{Environment.NewLine}{sbrpAttribute}");
+
+                    File.WriteAllText(TargetPath!, specContent);
+
+                }
+                return true;
+            }
+            return false;
+        }
+
+        [GeneratedRegex(@"\[assembly:\s+System\.Reflection\.AssemblyVersionAttribute\(""(?<version>[0-9.]+)""\)\]")]
+        private static partial Regex GetVersionRegex();
+
+        [GeneratedRegex(@"\[assembly:\s+AssemblyInformationalVersion\(""(?<version>.+ originated from source-build-reference-packages)""\)\]")]
+        private static partial Regex GetSbrpAttributeRegex();
+    }
+}