fix(cmake): use explicit variable for is config

Signed-off-by: Henry Schreiner <[email protected]>

CMakeLists.txt

@@ -247,6 +247,7 @@ else()
   set(PYBIND11_INSTALL OFF)
 endif()
 
+set(_pybind11_is_config OFF)
 include("${CMAKE_CURRENT_SOURCE_DIR}/tools/pybind11Common.cmake")
 # https://github.com/jtojnar/cmake-snips/#concatenating-paths-when-building-pkg-config-files
 # TODO: cmake 3.20 adds the cmake_path() function, which obsoletes this snippet

tools/pybind11Common.cmake

@@ -28,11 +28,7 @@ endif()
 # are in CONFIG mode, they should be "normal" targets instead.
 # In CMake 3.11+ you can promote a target to global after you create it,
 # which might be simpler than this check.
-get_property(
-  is_config
-  TARGET pybind11::pybind11_headers
-  PROPERTY IMPORTED)
-if(NOT is_config)
+if(NOT _pybind11_is_config)
   set(optional_global GLOBAL)
 endif()
 

tools/pybind11Config.cmake.in

@@ -84,7 +84,7 @@ you can either use the basic targets, or use the FindPython tools:
 
   # Python method:
   Python_add_library(MyModule2 src2.cpp)
-  target_link_libraries(MyModule2 pybind11::headers)
+  target_link_libraries(MyModule2 PUBLIC pybind11::headers)
   set_target_properties(MyModule2 PROPERTIES
                                   INTERPROCEDURAL_OPTIMIZATION ON
                                   CXX_VISIBILITY_PRESET ON
@@ -222,7 +222,7 @@ include("${CMAKE_CURRENT_LIST_DIR}/pybind11Targets.cmake")
 add_library(pybind11::headers IMPORTED INTERFACE)
 set_target_properties(pybind11::headers PROPERTIES INTERFACE_LINK_LIBRARIES
                                                    pybind11::pybind11_headers)
-
+set(_pybind11_is_config ON)
 include("${CMAKE_CURRENT_LIST_DIR}/pybind11Common.cmake")
 
 if(NOT pybind11_FIND_QUIETLY)