VS: Support C# project references

When specifying a pure C# target in the `target_link_libraries()` call to
another C++ target, a `<ProjectReference>` was setup for it (we wanted this)
but also a corresponding `.lib` was added under `<AdditionalDependencies>`
(we didn't want this).

This change introduces a check that prevents `.lib` linker options from
being used when the corresponding target for that library is a C# target.

Fixes: #17678

6 files changed, 79 insertions, 0 deletions

diff --git a/Tests/CSharpLinkFromCxx/.gitattributes b/Tests/CSharpLinkFromCxx/.gitattributes
new file mode 100644
index 0000000..57a39049
--- /dev/null
+++ b/Tests/CSharpLinkFromCxx/.gitattributes
@@ -0,0 +1 @@
+UsefulManagedCppClass.* -format.clang-format
diff --git a/Tests/CSharpLinkFromCxx/CMakeLists.txt b/Tests/CSharpLinkFromCxx/CMakeLists.txt
new file mode 100644
index 0000000..9a1a993
--- /dev/null
+++ b/Tests/CSharpLinkFromCxx/CMakeLists.txt
@@ -0,0 +1,19 @@
+# Take a C# shared library and link it to a managed C++ shared library
+cmake_minimum_required(VERSION 3.10)
+project (CSharpLinkFromCxx CXX CSharp)
+
+add_library(CSharpLibrary SHARED UsefulCSharpClass.cs)
+
+# we have to change the default flags for the
+# managed C++ project to build
+string(REPLACE "/EHsc" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+string(REPLACE "/RTC1" "" CMAKE_CXX_FLAGS_DEBUG ${CMAKE_CXX_FLAGS_DEBUG})
+
+# The C# project is a dependency of the C++/CLI project
+add_library(ManagedCppLibrary SHARED UsefulManagedCppClass.cpp UsefulManagedCppClass.hpp)
+target_compile_options(ManagedCppLibrary PRIVATE "/clr")
+target_link_libraries(ManagedCppLibrary PUBLIC CSharpLibrary)
+
+# Main executable for the test framework
+add_executable(CSharpLinkFromCxx CSharpLinkFromCxx.cs)
+target_link_libraries(CSharpLinkFromCxx PRIVATE ManagedCppLibrary)
diff --git a/Tests/CSharpLinkFromCxx/CSharpLinkFromCxx.cs b/Tests/CSharpLinkFromCxx/CSharpLinkFromCxx.cs
new file mode 100644
index 0000000..31a74eb
--- /dev/null
+++ b/Tests/CSharpLinkFromCxx/CSharpLinkFromCxx.cs
@@ -0,0 +1,16 @@
+using System;
+using CSharpLibrary;
+
+namespace CSharpLinkFromCxx
+{
+    internal class CSharpLinkFromCxx
+    {
+        public static void Main(string[] args)
+        {
+            Console.WriteLine("Starting test for CSharpLinkFromCxx");
+
+            var useful = new UsefulManagedCppClass();
+            useful.RunTest();
+        }
+    }
+}
diff --git a/Tests/CSharpLinkFromCxx/UsefulCSharpClass.cs b/Tests/CSharpLinkFromCxx/UsefulCSharpClass.cs
new file mode 100644
index 0000000..749e57d
--- /dev/null
+++ b/Tests/CSharpLinkFromCxx/UsefulCSharpClass.cs
@@ -0,0 +1,12 @@
+using System;
+
+namespace CSharpLibrary
+{
+    public class UsefulCSharpClass
+    {
+        public string GetSomethingUseful()
+        {
+            return "Something Useful";
+        }
+    }
+}
diff --git a/Tests/CSharpLinkFromCxx/UsefulManagedCppClass.cpp b/Tests/CSharpLinkFromCxx/UsefulManagedCppClass.cpp
new file mode 100644
index 0000000..9468812
--- /dev/null
+++ b/Tests/CSharpLinkFromCxx/UsefulManagedCppClass.cpp
@@ -0,0 +1,15 @@
+#include "UsefulManagedCppClass.hpp"
+
+namespace CSharpLibrary
+{
+    UsefulManagedCppClass::UsefulManagedCppClass()
+    {
+        auto useful = gcnew UsefulCSharpClass();
+        m_usefulString = useful->GetSomethingUseful();
+    }
+
+    void UsefulManagedCppClass::RunTest()
+    {
+        Console::WriteLine("Printing from Managed CPP Class: " + m_usefulString);
+    }
+}
diff --git a/Tests/CSharpLinkFromCxx/UsefulManagedCppClass.hpp b/Tests/CSharpLinkFromCxx/UsefulManagedCppClass.hpp
new file mode 100644
index 0000000..def7cea
--- /dev/null
+++ b/Tests/CSharpLinkFromCxx/UsefulManagedCppClass.hpp
@@ -0,0 +1,16 @@
+using namespace System;
+
+namespace CSharpLibrary
+{
+    public ref class UsefulManagedCppClass
+    {
+    public:
+
+        UsefulManagedCppClass();
+        void RunTest();
+
+    private:
+
+        String^ m_usefulString;
+    };
+}