Overcome the `ref struct` limitation for pre-roslyn compilers by introducing GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE for generated code (#7490)
* enable compatibility mode in codegen
* regenerate protos
* improve readability
* more robust way of figuring out path to old C# compiler
* add recent C# changes
diff --git a/csharp/src/Google.Protobuf.Test/RefStructCompatibilityTest.cs b/csharp/src/Google.Protobuf.Test/RefStructCompatibilityTest.cs
new file mode 100644
index 0000000..f2d9a2d
--- /dev/null
+++ b/csharp/src/Google.Protobuf.Test/RefStructCompatibilityTest.cs
@@ -0,0 +1,119 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc. All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using NUnit.Framework;
+using System.Diagnostics;
+using System;
+using System.Reflection;
+using System.IO;
+
+namespace Google.Protobuf
+{
+ public class RefStructCompatibilityTest
+ {
+ /// <summary>
+ /// Checks that the generated code can be compiler with an old C# compiler.
+ /// The reason why this test is needed is that even though dotnet SDK projects allow to set LangVersion,
+ /// this setting doesn't accurately simulate compilation with an actual old pre-roslyn C# compiler.
+ /// For instance, the "ref struct" types are only supported by C# 7.2 and higher, but even if
+ /// LangVersion is set low, the roslyn compiler still understands the concept of ref struct
+ /// and silently accepts them. Therefore we try to build the generated code with an actual old C# compiler
+ /// to be able to catch these sort of compatibility problems.
+ /// </summary>
+ [Test]
+ public void GeneratedCodeCompilesWithOldCsharpCompiler()
+ {
+ if (Environment.OSVersion.Platform != PlatformID.Win32NT)
+ {
+ // This tests needs old C# compiler which is only available on Windows. Skipping it on all other platforms.
+ return;
+ }
+
+ var currentAssemblyDir = Path.GetDirectoryName(typeof(RefStructCompatibilityTest).GetTypeInfo().Assembly.Location);
+ var testProtosProjectDir = Path.GetFullPath(Path.Combine(currentAssemblyDir, "..", "..", "..", "..", "Google.Protobuf.Test.TestProtos"));
+ var testProtosOutputDir = (currentAssemblyDir.Contains("bin/Debug/") || currentAssemblyDir.Contains("bin\\Debug\\")) ? "bin\\Debug\\net45" : "bin\\Release\\net45";
+
+ // If "ref struct" types are used in the generated code, compilation with an old compiler will fail with the following error:
+ // "XYZ is obsolete: 'Types with embedded references are not supported in this version of your compiler.'"
+ // We build the code with GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE to avoid the use of ref struct in the generated code.
+ var compatibilityFlag = "-define:GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE";
+ var sources = "*.cs"; // the generated sources from the TestProtos project
+ var args = $"-langversion:3 -target:library {compatibilityFlag} -reference:{testProtosOutputDir}\\Google.Protobuf.dll -out:{testProtosOutputDir}\\TestProtos.RefStructCompatibilityTest.OldCompiler.dll {sources}";
+ RunOldCsharpCompilerAndCheckSuccess(args, testProtosProjectDir);
+ }
+
+ /// <summary>
+ /// Invoke an old C# compiler in a subprocess and check it finished successful.
+ /// </summary>
+ /// <param name="args"></param>
+ /// <param name="workingDirectory"></param>
+ private void RunOldCsharpCompilerAndCheckSuccess(string args, string workingDirectory)
+ {
+ using (var process = new Process())
+ {
+ // Get the path to the old C# 5 compiler from .NET framework. This approach is not 100% reliable, but works on most machines.
+ // Alternative way of getting the framework path is System.Runtime.InteropServices.RuntimeEnvironment.GetRuntimeDirectory()
+ // but it only works with the net45 target.
+ var oldCsharpCompilerPath = Path.Combine(Environment.GetEnvironmentVariable("WINDIR"), "Microsoft.NET", "Framework", "v4.0.30319", "csc.exe");
+ process.StartInfo.FileName = oldCsharpCompilerPath;
+ process.StartInfo.RedirectStandardOutput = true;
+ process.StartInfo.RedirectStandardError = true;
+ process.StartInfo.UseShellExecute = false;
+ process.StartInfo.Arguments = args;
+ process.StartInfo.WorkingDirectory = workingDirectory;
+
+ process.OutputDataReceived += (sender, e) =>
+ {
+ if (e.Data != null)
+ {
+ Console.WriteLine(e.Data);
+ }
+ };
+ process.ErrorDataReceived += (sender, e) =>
+ {
+ if (e.Data != null)
+ {
+ Console.WriteLine(e.Data);
+ }
+ };
+
+ process.Start();
+
+ process.BeginErrorReadLine();
+ process.BeginOutputReadLine();
+
+ process.WaitForExit();
+ Assert.AreEqual(0, process.ExitCode);
+ }
+ }
+ }
+}
\ No newline at end of file
