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

2 files changed, 27 insertions, 18 deletions

diff --git a/Source/cmGlobalVisualStudioGenerator.cxx b/Source/cmGlobalVisualStudioGenerator.cxx
index a4570e1..fa7dc51 100644
--- a/Source/cmGlobalVisualStudioGenerator.cxx
+++ b/Source/cmGlobalVisualStudioGenerator.cxx
@@ -737,26 +737,24 @@ bool cmGlobalVisualStudioGenerator::TargetIsFortranOnly(
 bool cmGlobalVisualStudioGenerator::TargetIsCSharpOnly(
   cmGeneratorTarget const* gt)
 {
-  // check to see if this is a C# build
-  std::set<std::string> languages;
-  {
-    // Issue diagnostic if the source files depend on the config.
-    std::vector<cmSourceFile*> sources;
-    if (!gt->GetConfigCommonSourceFiles(sources)) {
-      return false;
-    }
-    // Only "real" targets are allowed to be C# targets.
-    if (gt->Target->GetType() > cmStateEnums::OBJECT_LIBRARY) {
-      return false;
-    }
+  // C# targets can be defined with add_library() (using SHARED or STATIC) and
+  // also using add_executable(). We do not treat imported C# targets the same
+  // (these come in as UTILITY)
+  if (gt->GetType() != cmStateEnums::SHARED_LIBRARY &&
+      gt->GetType() != cmStateEnums::STATIC_LIBRARY &&
+      gt->GetType() != cmStateEnums::EXECUTABLE) {
+    return false;
   }
-  gt->GetLanguages(languages, "");
-  if (languages.size() == 1) {
-    if (*languages.begin() == "CSharp") {
-      return true;
-    }
+
+  // Issue diagnostic if the source files depend on the config.
+  std::vector<cmSourceFile*> sources;
+  if (!gt->GetConfigCommonSourceFiles(sources)) {
+    return false;
   }
-  return false;
+
+  std::set<std::string> languages;
+  gt->GetLanguages(languages, "");
+  return languages.size() == 1 && languages.count("CSharp") > 0;
 }
 
 bool cmGlobalVisualStudioGenerator::TargetCanBeReferenced(
diff --git a/Source/cmVisualStudio10TargetGenerator.cxx b/Source/cmVisualStudio10TargetGenerator.cxx
index 92d67db..48a5c0a 100644
--- a/Source/cmVisualStudio10TargetGenerator.cxx
+++ b/Source/cmVisualStudio10TargetGenerator.cxx
@@ -3451,6 +3451,17 @@ void cmVisualStudio10TargetGenerator::AddLibraries(
   std::string currentBinDir =
     this->LocalGenerator->GetCurrentBinaryDirectory();
   for (cmComputeLinkInformation::Item const& l : libs) {
+    // Do not allow C# targets to be added to the LIB listing. LIB files are
+    // used for linking C++ dependencies. C# libraries do not have lib files.
+    // Instead, they compile down to C# reference libraries (DLL files). The
+    // `<ProjectReference>` elements added to the vcxproj are enough for the
+    // IDE to deduce the DLL file required by other C# projects that need its
+    // reference library.
+    if (l.Target &&
+        cmGlobalVisualStudioGenerator::TargetIsCSharpOnly(l.Target)) {
+      continue;
+    }
+
     if (l.IsPath) {
       std::string path =
         this->LocalGenerator->ConvertToRelativePath(currentBinDir, l.Value);