Use cmake v3.23 FILE_SET HEADERS

[ClausKlein]

if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.23.0")
  # cmake-format: off
  target_sources(
    shared_shared PUBLIC
      FILE_SET HEADERS
      BASE_DIRS include
        ${PROJECT_BINARY_DIR}/export
      FILES include/shared/shared.hpp
        ${PROJECT_BINARY_DIR}/export/shared/shared_export.hpp
  )
  # cmake-format: on
else()
  target_sources(shared_shared PUBLIC include/shared/shared.hpp)
endif()

and

diff --git a/cmake/install-rules.cmake b/cmake/install-rules.cmake
index 7fbbdcf..c863424 100644
--- a/cmake/install-rules.cmake
+++ b/cmake/install-rules.cmake
@@ -12,13 +12,18 @@ include(GNUInstallDirs)
 # find_package(<package>) call for consumers to find this project
 set(package shared)
 
-install(
-    DIRECTORY
-    include/
-    "${PROJECT_BINARY_DIR}/export/"
-    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
-    COMPONENT shared_Development
-)
+if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.23.0")
+    # required in CMake 3.23 and more
+    set(FILE_SET_ARGS "FILE_SET" "HEADERS")
+else()
+    install(
+        DIRECTORY
+        include/
+        "${PROJECT_BINARY_DIR}/export/"
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+        COMPONENT shared_Development
+    )
+endif()
 
 install(
     TARGETS shared_shared
@@ -32,6 +37,7 @@ install(
     COMPONENT shared_Development
     INCLUDES #
     DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+    ${FILE_SET_ARGS} # FILE_SET HEADERS
 )
 
 write_basic_package_version_file(

[friendlyanon]

Just an FYI, but if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.23.0") is wrong, it should be if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.23.0").

I don't intend to add conditional logic like this. It adds unnecessary complexity to the generated code. Templates until C++23 will be kept as is. Templates starting with C++23 will start making use of the appropriate CMake additions, since C++23 is supported only in recent releases.

[ClausKlein]

OK, my minimum cmake version is 3.25...3.29 today