UseSWIG: Add CSHARP variant for wrapper files

Issue: #18065
Fixes: #18066

6 files changed, 103 insertions, 2 deletions

diff --git a/Help/release/3.12.rst b/Help/release/3.12.rst
index e460d81d16..691731a469 100644
--- a/Help/release/3.12.rst
+++ b/Help/release/3.12.rst
@@ -189,6 +189,9 @@ Modules
   ``UseSWIG_MODULE_VERSION`` variable to ensure legacy support as well as more
   robust handling of ``SWIG`` advanced features (like ``%template``).
 
+* The :module:`UseSWIG` module learned to support CSHARP variant
+  wrapper files.
+
 * The :module:`WriteCompilerDetectionHeader` module gained a ``BARE_FEATURES``
   option to add a compatibility define for the exact keyword of a new language
   feature.
diff --git a/Modules/UseSWIG.cmake b/Modules/UseSWIG.cmake
index 8713cd8be5..98a761226a 100644
--- a/Modules/UseSWIG.cmake
+++ b/Modules/UseSWIG.cmake
@@ -189,6 +189,7 @@ set(SWIG_EXTRA_LIBRARIES "")
 
 set(SWIG_PYTHON_EXTRA_FILE_EXTENSIONS ".py")
 set(SWIG_JAVA_EXTRA_FILE_EXTENSIONS ".java" "JNI.java")
+set(SWIG_CSHARP_EXTRA_FILE_EXTENSIONS ".cs" "PINVOKE.cs")
 
 ##
 ## PRIVATE functions
@@ -263,10 +264,14 @@ function(SWIG_GET_EXTRA_OUTPUT_FILES language outfiles generatedpath infile)
   endif()
   foreach(it ${SWIG_${language}_EXTRA_FILE_EXTENSIONS})
     set(extra_file "${generatedpath}/${module_basename}${it}")
+    if (extra_file MATCHES "\\.cs$")
+      set_source_files_properties(${extra_file} PROPERTIES LANGUAGE "CSharp")
+    else()
+      # Treat extra outputs as plain files regardless of language.
+      set_source_files_properties(${extra_file} PROPERTIES LANGUAGE "")
+    endif()
     list(APPEND files "${extra_file}")
   endforeach()
-    # Treat extra outputs as plain files regardless of language.
-  set_source_files_properties(${files} PROPERTIES LANGUAGE "")
 
   set (${outfiles} ${files} PARENT_SCOPE)
 endfunction()
diff --git a/Tests/UseSWIG/BasicConfiguration.cmake b/Tests/UseSWIG/BasicConfiguration.cmake
index d025d2a968..fd3ac4031d 100644
--- a/Tests/UseSWIG/BasicConfiguration.cmake
+++ b/Tests/UseSWIG/BasicConfiguration.cmake
@@ -15,6 +15,9 @@ unset(SWIG_LANG_DEFINITIONS)
 unset(SWIG_LANG_OPTIONS)
 unset(SWIG_LANG_LIBRARIES)
 
+if(${language} MATCHES csharp)
+  set(SWIG_LANG_TYPE TYPE SHARED)
+endif()
 if(${language} MATCHES python)
   find_package(Python REQUIRED COMPONENTS Interpreter Development)
   set(SWIG_LANG_INCLUDE_DIRECTORIES ${Python_INCLUDE_DIRS})
@@ -76,4 +79,5 @@ SWIG_ADD_LIBRARY(example
                  ${SWIG_LANG_TYPE}
                  SOURCES "${CMAKE_CURRENT_LIST_DIR}/example.i"
                          "${CMAKE_CURRENT_LIST_DIR}/example.cxx")
+TARGET_INCLUDE_DIRECTORIES(example PUBLIC ${CMAKE_CURRENT_LIST_DIR})
 TARGET_LINK_LIBRARIES(example PRIVATE ${SWIG_LANG_LIBRARIES})
diff --git a/Tests/UseSWIG/BasicCsharp/CMakeLists.txt b/Tests/UseSWIG/BasicCsharp/CMakeLists.txt
new file mode 100644
index 0000000000..84743efa03
--- /dev/null
+++ b/Tests/UseSWIG/BasicCsharp/CMakeLists.txt
@@ -0,0 +1,21 @@
+cmake_minimum_required(VERSION 3.12)
+
+project(TestBasicCsharp CXX CSharp)
+
+include(CTest)
+
+set(language "csharp")
+
+include (../BasicConfiguration.cmake)
+
+set_source_files_properties(Square.cs Circle.cs Shape.cs PROPERTIES GENERATED 1)
+add_library(example_cs SHARED  $<TARGET_PROPERTY:example,SWIG_SUPPORT_FILES> Square.cs Circle.cs Shape.cs)
+set_target_properties(example_cs PROPERTIES LINKER_LANGUAGE CSharp)
+target_link_libraries(example_cs example)
+
+add_executable(runme ${CMAKE_CURRENT_SOURCE_DIR}/../runme.cs)
+target_link_libraries(runme example_cs)
+set_target_properties(runme PROPERTIES LINKER_LANGUAGE CSharp)
+
+add_test (NAME BasicCsharp
+  COMMAND $<TARGET_FILE:runme>)
diff --git a/Tests/UseSWIG/CMakeLists.txt b/Tests/UseSWIG/CMakeLists.txt
index 0c4ec8a7f5..cc29b77000 100644
--- a/Tests/UseSWIG/CMakeLists.txt
+++ b/Tests/UseSWIG/CMakeLists.txt
@@ -19,6 +19,20 @@ add_test(NAME UseSWIG.LegacyPerl COMMAND
   --test-command ${CMAKE_CTEST_COMMAND} -V -C $<CONFIGURATION>
   )
 
+include(CheckLanguage)
+check_language(CSharp)
+if (CMAKE_CSharp_COMPILER)
+  add_test(NAME UseSWIG.BasicCsharp COMMAND
+    ${CMAKE_CTEST_COMMAND} -C $<CONFIGURATION>
+    --build-and-test
+    "${CMake_SOURCE_DIR}/Tests/UseSWIG/BasicCsharp"
+    "${CMake_BINARY_DIR}/Tests/UseSWIG/BasicCsharp"
+    ${build_generator_args}
+    --build-project TestBasicCsharp
+    --build-options ${build_options}
+    --test-command ${CMAKE_CTEST_COMMAND} -V -C $<CONFIGURATION>
+    )
+endif()
 
 add_test(NAME UseSWIG.BasicPython COMMAND
   ${CMAKE_CTEST_COMMAND} -C $<CONFIGURATION>
diff --git a/Tests/UseSWIG/runme.cs b/Tests/UseSWIG/runme.cs
new file mode 100644
index 0000000000..f0c1bd2200
--- /dev/null
+++ b/Tests/UseSWIG/runme.cs
@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+
+public class runme
+{
+    static void Main()
+    {
+        // ----- Object creation -----
+
+        Console.WriteLine("Creating some objects:");
+        Circle c = new Circle(10);
+        Console.WriteLine("    Created " + c);
+        Square s = new Square(10);
+        Console.WriteLine("    Created " + s);
+
+        // ----- Access a static member -----
+
+        Console.WriteLine("\nA total of " + Shape.nshapes + " shapes were created");
+
+        // ----- Member data access -----
+
+        // Set the location of the object
+
+        c.x = 20;
+        c.y = 30;
+
+        s.x = -10;
+        s.y = 5;
+
+        Console.WriteLine("\nHere is their current position:");
+        Console.WriteLine("    Circle = ({0}, {1})", c.x,c.y);
+        Console.WriteLine("    Square = ({0}, {1})", s.x,s.y);
+
+        // ----- Call some methods -----
+
+        Console.WriteLine("\nHere are some properties of the shapes:");
+        List <Shape> shapeList = new List <Shape> { c,s };
+        foreach(var o in shapeList){
+              Console.WriteLine("   " + o);
+              Console.WriteLine("        area      = " + o.area());
+              Console.WriteLine("        perimeter = " + o.perimeter());
+        }
+
+        Console.WriteLine("\nGuess I'll clean up now");
+
+        // Note: this invokes the virtual destructor
+        c.Dispose();
+        s.Dispose();
+
+        s = new Square(10);;
+        Console.WriteLine(Shape.nshapes + " shapes remain");
+        Console.WriteLine("Goodbye");
+    }
+}