cmGeneratorTarget: classify BMI-only C++ module sources

Source/cmFileAPICodemodel.cxx

@@ -1678,6 +1678,7 @@ Json::Value Target::DumpSource(cmGeneratorTarget::SourceAndKind const& sk,
   }
 
   switch (sk.Kind) {
+    case cmGeneratorTarget::SourceKindCxxModuleSource:
     case cmGeneratorTarget::SourceKindObjectSource: {
       source["compileGroupIndex"] =
         this->AddSourceCompileGroup(sk.Source.Value, si);

Source/cmGeneratorTarget.cxx

@@ -1071,6 +1071,12 @@ void cmGeneratorTarget::GetHeaderSources(
   IMPLEMENT_VISIT(SourceKindHeader);
 }
 
+void cmGeneratorTarget::GetCxxModuleSources(
+  std::vector<cmSourceFile const*>& data, const std::string& config) const
+{
+  IMPLEMENT_VISIT(SourceKindCxxModuleSource);
+}
+
 void cmGeneratorTarget::GetExtraSources(std::vector<cmSourceFile const*>& data,
                                         const std::string& config) const
 {
@@ -1953,8 +1959,12 @@ void cmGeneratorTarget::ComputeKindedSources(KindedSources& files,
     // Compute the kind (classification) of this source file.
     SourceKind kind;
     std::string ext = cmSystemTools::LowerCase(sf->GetExtension());
+    cmFileSet const* fs = this->GetFileSetForSource(config, sf);
     if (sf->GetCustomCommand()) {
       kind = SourceKindCustomCommand;
+    } else if (!this->Target->IsNormal() && !this->Target->IsImported() &&
+               fs && (fs->GetType() == "CXX_MODULES"_s)) {
+      kind = SourceKindCxxModuleSource;
     } else if (this->Target->GetType() == cmStateEnums::UTILITY ||
                this->Target->GetType() == cmStateEnums::INTERFACE_LIBRARY
                // XXX(clang-tidy): https://bugs.llvm.org/show_bug.cgi?id=44165

Source/cmGeneratorTarget.h

@@ -116,6 +116,7 @@ public:
     SourceKindCertificate,
     SourceKindCustomCommand,
     SourceKindExternalObject,
+    SourceKindCxxModuleSource,
     SourceKindExtra,
     SourceKindHeader,
     SourceKindIDL,
@@ -186,6 +187,8 @@ public:
                           const std::string& config) const;
   void GetHeaderSources(std::vector<cmSourceFile const*>&,
                         const std::string& config) const;
+  void GetCxxModuleSources(std::vector<cmSourceFile const*>&,
+                           const std::string& config) const;
   void GetExtraSources(std::vector<cmSourceFile const*>&,
                        const std::string& config) const;
   void GetCustomCommands(std::vector<cmSourceFile const*>&,

Source/cmVisualStudio10TargetGenerator.cxx

@@ -2517,6 +2517,7 @@ void cmVisualStudio10TargetGenerator::WriteAllSources(Elem& e0)
       case cmGeneratorTarget::SourceKindModuleDefinition:
         tool = "None";
         break;
+      case cmGeneratorTarget::SourceKindCxxModuleSource:
       case cmGeneratorTarget::SourceKindUnityBatched:
       case cmGeneratorTarget::SourceKindObjectSource: {
         const std::string& lang = si.Source->GetLanguage();