cxxmodules: include INCLUDES DESTINATION directories

These paths are added outside the normal property management mechanisms.
Shuttle the value to the C++ module export as needed.

Fixes: #25289

Source/cmExportBuildFileGenerator.cxx

@@ -127,7 +127,7 @@ bool cmExportBuildFileGenerator::GenerateMainFile(std::ostream& os)
 
     std::string errorMessage;
     if (!this->PopulateCxxModuleExportProperties(
-          gte, properties, cmGeneratorExpression::BuildInterface,
+          gte, properties, cmGeneratorExpression::BuildInterface, {},
           errorMessage)) {
       this->LG->GetGlobalGenerator()->GetCMakeInstance()->IssueMessage(
         MessageType::FATAL_ERROR, errorMessage,

Source/cmExportFileGenerator.cxx

@@ -374,10 +374,13 @@ void cmExportFileGenerator::PopulateSourcesInterface(
 void cmExportFileGenerator::PopulateIncludeDirectoriesInterface(
   cmGeneratorTarget const* target,
   cmGeneratorExpression::PreprocessContext preprocessRule,
-  ImportPropertyMap& properties, cmTargetExport const& te)
+  ImportPropertyMap& properties, cmTargetExport const& te,
+  std::string& includesDestinationDirs)
 {
   assert(preprocessRule == cmGeneratorExpression::InstallInterface);
 
+  includesDestinationDirs.clear();
+
   const char* propName = "INTERFACE_INCLUDE_DIRECTORIES";
   cmValue input = target->GetProperty(propName);
 
@@ -414,6 +417,7 @@ void cmExportFileGenerator::PopulateIncludeDirectoriesInterface(
   }
 
   prefixItems(exportDirs);
+  includesDestinationDirs = exportDirs;
 
   std::string includes = (input ? *input : "");
   const char* sep = input ? ";" : "";
@@ -1260,8 +1264,23 @@ enum class PropertyType
 {
   Strings,
   Paths,
+  IncludePaths,
 };
 
+namespace {
+bool PropertyTypeIsForPaths(PropertyType pt)
+{
+  switch (pt) {
+    case PropertyType::Strings:
+      return false;
+    case PropertyType::Paths:
+    case PropertyType::IncludePaths:
+      return true;
+  }
+  return false;
+}
+}
+
 struct ModulePropertyTable
 {
   cm::static_string_view Name;
@@ -1270,7 +1289,8 @@ struct ModulePropertyTable
 
 bool cmExportFileGenerator::PopulateCxxModuleExportProperties(
   cmGeneratorTarget const* gte, ImportPropertyMap& properties,
-  cmGeneratorExpression::PreprocessContext ctx, std::string& errorMessage)
+  cmGeneratorExpression::PreprocessContext ctx,
+  std::string const& includesDestinationDirs, std::string& errorMessage)
 {
   if (!gte->HaveCxx20ModuleSources(&errorMessage)) {
     return true;
@@ -1292,7 +1312,7 @@ bool cmExportFileGenerator::PopulateCxxModuleExportProperties(
   }
 
   const ModulePropertyTable exportedModuleProperties[] = {
-    { "INCLUDE_DIRECTORIES"_s, PropertyType::Paths },
+    { "INCLUDE_DIRECTORIES"_s, PropertyType::IncludePaths },
     { "COMPILE_DEFINITIONS"_s, PropertyType::Strings },
     { "COMPILE_OPTIONS"_s, PropertyType::Strings },
     { "COMPILE_FEATURES"_s, PropertyType::Strings },
@@ -1310,9 +1330,16 @@ bool cmExportFileGenerator::PopulateCxxModuleExportProperties(
       properties[exportedPropName] =
         cmGeneratorExpression::Preprocess(*prop, ctx);
       if (ctx == cmGeneratorExpression::InstallInterface &&
-          propEntry.Type == PropertyType::Paths) {
+          PropertyTypeIsForPaths(propEntry.Type)) {
         this->ReplaceInstallPrefix(properties[exportedPropName]);
         prefixItems(properties[exportedPropName]);
+        if (propEntry.Type == PropertyType::IncludePaths &&
+            !includesDestinationDirs.empty()) {
+          if (!properties[exportedPropName].empty()) {
+            properties[exportedPropName] += ';';
+          }
+          properties[exportedPropName] += includesDestinationDirs;
+        }
       }
     }
   }

Source/cmExportFileGenerator.h

@@ -143,7 +143,8 @@ protected:
   void PopulateIncludeDirectoriesInterface(
     cmGeneratorTarget const* target,
     cmGeneratorExpression::PreprocessContext preprocessRule,
-    ImportPropertyMap& properties, cmTargetExport const& te);
+    ImportPropertyMap& properties, cmTargetExport const& te,
+    std::string& includesDestinationDirs);
   void PopulateSourcesInterface(
     cmGeneratorTarget const* target,
     cmGeneratorExpression::PreprocessContext preprocessRule,
@@ -177,7 +178,8 @@ protected:
 
   bool PopulateCxxModuleExportProperties(
     cmGeneratorTarget const* gte, ImportPropertyMap& properties,
-    cmGeneratorExpression::PreprocessContext ctx, std::string& errorMessage);
+    cmGeneratorExpression::PreprocessContext ctx,
+    std::string const& includesDestinationDirs, std::string& errorMessage);
   bool PopulateExportProperties(cmGeneratorTarget const* gte,
                                 ImportPropertyMap& properties,
                                 std::string& errorMessage);

Source/cmExportInstallFileGenerator.cxx

@@ -92,8 +92,10 @@ bool cmExportInstallFileGenerator::GenerateMainFile(std::ostream& os)
 
     ImportPropertyMap properties;
 
+    std::string includesDestinationDirs;
     this->PopulateIncludeDirectoriesInterface(
-      gt, cmGeneratorExpression::InstallInterface, properties, *te);
+      gt, cmGeneratorExpression::InstallInterface, properties, *te,
+      includesDestinationDirs);
     this->PopulateSourcesInterface(gt, cmGeneratorExpression::InstallInterface,
                                    properties);
     this->PopulateInterfaceProperty("INTERFACE_SYSTEM_INCLUDE_DIRECTORIES", gt,
@@ -128,7 +130,7 @@ bool cmExportInstallFileGenerator::GenerateMainFile(std::ostream& os)
     std::string errorMessage;
     if (!this->PopulateCxxModuleExportProperties(
           gt, properties, cmGeneratorExpression::InstallInterface,
-          errorMessage)) {
+          includesDestinationDirs, errorMessage)) {
       cmSystemTools::Error(errorMessage);
       return false;
     }

Tests/RunCMake/CXXModules/examples/export-include-directories-build/CMakeLists.txt

@@ -4,7 +4,8 @@ project(cxx_modules_export_include_directories CXX)
 include("${CMAKE_SOURCE_DIR}/../cxx-modules-rules.cmake")
 
 add_library(export_include_directories STATIC
-  include/include.h)
+  include/include.h
+  includes/includes.h)
 target_sources(export_include_directories
   PRIVATE
     forward.cxx
@@ -25,7 +26,8 @@ target_sources(export_include_directories
 target_compile_features(export_include_directories PUBLIC cxx_std_20)
 target_include_directories(export_include_directories
   PRIVATE
-    "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>")
+    "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>"
+    "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/includes>")
 
 add_library(no_modules STATIC no_modules.cxx)
 

Tests/RunCMake/CXXModules/examples/export-include-directories-build/importable.cxx

@@ -6,6 +6,12 @@ module;
 #  error "include define not found"
 #endif
 
+#include "includes/includes.h"
+
+#ifndef includes_h_included
+#  error "includes define not found"
+#endif
+
 export module importable;
 
 extern "C++" {

Tests/RunCMake/CXXModules/examples/export-include-directories-build/includes/includes.h

@@ -0,0 +1,3 @@
+#pragma once
+
+#define includes_h_included

Tests/RunCMake/CXXModules/examples/export-include-directories-install/CMakeLists.txt

@@ -4,7 +4,8 @@ project(cxx_modules_export_include_directories CXX)
 include("${CMAKE_SOURCE_DIR}/../cxx-modules-rules.cmake")
 
 add_library(export_include_directories STATIC
-  include/include.h)
+  include/include.h
+  includes/includes.h)
 target_sources(export_include_directories
   PRIVATE
     forward.cxx
@@ -26,15 +27,19 @@ target_compile_features(export_include_directories PUBLIC cxx_std_20)
 target_include_directories(export_include_directories
   PRIVATE
     "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>"
+    "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/includes>"
     "$<INSTALL_INTERFACE:include>")
 
 add_library(no_modules STATIC no_modules.cxx)
 
 install(TARGETS export_include_directories no_modules
   EXPORT CXXModules
-  FILE_SET modules DESTINATION "lib/cxx/miu")
+  FILE_SET modules DESTINATION "lib/cxx/miu"
+  INCLUDES DESTINATION "elsewhere")
 install(DIRECTORY include
   DESTINATION "include")
+install(DIRECTORY includes
+  DESTINATION "elsewhere")
 install(EXPORT CXXModules
   NAMESPACE CXXModules::
   DESTINATION "lib/cmake/export_include_directories"

Tests/RunCMake/CXXModules/examples/export-include-directories-install/importable.cxx

@@ -6,6 +6,12 @@ module;
 #  error "include define not found"
 #endif
 
+#include "includes/includes.h"
+
+#ifndef includes_h_included
+#  error "includes define not found"
+#endif
+
 export module importable;
 
 extern "C++" {

Tests/RunCMake/CXXModules/examples/export-include-directories-install/includes/includes.h

@@ -0,0 +1,3 @@
+#pragma once
+
+#define includes_h_included