[CMake] Simplify writing of modulemap.

Instead of a two-step process that writes the dynamic contents at
CMake configure time, and a build-time step that concatenates the static
and dynamic part of the modulemap, CMake's configure_file() is used to
directly write the full contents at configure time.
As usual for configure files, the time stamp only changes when the file
contents change, so spurious rebuilds of the modules are avoided.

Author: hageboeck

CMakeLists.txt

@@ -421,36 +421,14 @@ get_property(__allBuiltins GLOBAL PROPERTY ROOT_BUILTIN_TARGETS)
 add_custom_target(move_headers ALL DEPENDS ${__allHeaders} ${__allBuiltins} gitinfotxt)
 
 #---CXX MODULES-----------------------------------------------------------------------------------
-if(MSVC)
-  set(_os_cat "type")
-else()
-  set(_os_cat "cat")
-endif()
-cmake_path(CONVERT "${CMAKE_BINARY_DIR}/include/module.modulemap.extra" TO_NATIVE_PATH_LIST _from_native)
-cmake_path(CONVERT "${CMAKE_BINARY_DIR}/include/ROOT.modulemap" TO_NATIVE_PATH_LIST _to_native)
-
-add_custom_target(copymodulemap DEPENDS "${CMAKE_BINARY_DIR}/include/ROOT.modulemap")
-add_custom_command(
-		  OUTPUT "${CMAKE_BINARY_DIR}/include/ROOT.modulemap"
-                  DEPENDS cmake/unix/module.modulemap "${CMAKE_BINARY_DIR}/include/module.modulemap.extra"
-		  COMMAND ${CMAKE_COMMAND} -E copy "${CMAKE_SOURCE_DIR}/cmake/unix/module.modulemap" "${CMAKE_BINARY_DIR}/include/ROOT.modulemap"
-                  COMMAND ${_os_cat} "${_from_native}" >> "${_to_native}"
-)
-install(FILES "${CMAKE_BINARY_DIR}/include/ROOT.modulemap" DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} COMPONENT headers)
-
-add_dependencies(move_headers copymodulemap)
-
 # Take all the modulemap contents we collected from the packages and append them to our modulemap.
 # We have to delay this because the ROOT_CXXMODULES_EXTRA_MODULEMAP_CONTENT is filled in the
 # add_subdirectory calls above.
 get_property(__modulemap_extra_content GLOBAL PROPERTY ROOT_CXXMODULES_EXTRA_MODULEMAP_CONTENT)
-string(REPLACE ";" "" __modulemap_extra_content "${__modulemap_extra_content}")
-# Write module.modulemap.extra to a temporary file first, to not touch module.modulemap.extra
-# if it's unchanged.
-file(WRITE "${CMAKE_BINARY_DIR}/include/module.modulemap.extra.tmp" "${__modulemap_extra_content}")
-configure_file("${CMAKE_BINARY_DIR}/include/module.modulemap.extra.tmp"
-    "${CMAKE_BINARY_DIR}/include/module.modulemap.extra"
-    COPYONLY)
+string(REPLACE ";" "" ROOT_GENERATED_MODULEMAP_CONTENT "${__modulemap_extra_content}")
+# Now append the generated content to the original modulemap
+configure_file(${CMAKE_SOURCE_DIR}/cmake/unix/module.modulemap ${CMAKE_BINARY_DIR}/include/ROOT.modulemap)
+install(FILES "${CMAKE_BINARY_DIR}/include/ROOT.modulemap" DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} COMPONENT headers)
 
 # From now on we handled all exposed module and want to make all new modulemaps private to ROOT.
 set(ROOT_CXXMODULES_WRITE_TO_CURRENT_DIR ON)

cmake/modules/RootMacros.cmake

@@ -558,7 +558,7 @@ function(ROOT_GENERATE_DICTIONARY dictionary)
         set(cpp_module_file ${library_output_dir}/${cpp_module}.pcm)
         # The module depends on its modulemap file.
         if (cpp_module_file AND CMAKE_PROJECT_NAME STREQUAL ROOT)
-		set (runtime_cxxmodule_dependencies copymodulemap "${CMAKE_BINARY_DIR}/include/ROOT.modulemap")
+		set (runtime_cxxmodule_dependencies "${CMAKE_BINARY_DIR}/include/ROOT.modulemap")
         endif()
       endif(cpp_module)
     endif()

cmake/unix/module.modulemap

@@ -70,3 +70,4 @@ module "Graf3D.X3DBuffer.h_C" {
 }
 
 // From this point on the contents of this file are automatically generated.
+@ROOT_GENERATED_MODULEMAP_CONTENT@