conan: [problem] cmake_multi INTERFACE_LINK_LIBRARIES uses generator expressions, does not support custom build configurations

I hope I have understood this problem correctly, and that I’ll be able to explain it properly.

The cmake_multi generator defines imported targets and sets properties on them that specify where the include and library files are located.

Here’s an example for GLEW, formatted for a bit of clarity:

CONAN_PKG::glew INTERFACE_LINK_LIBRARIES = 

CONAN_PKG::opengl;
CONAN_PKG::glu;

$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:>;
$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,MODULE_LIBRARY>:>;
$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:>;

$<$<CONFIG:Release>:
  CONAN_LIB::glew_glew32release;
  CONAN_PKG::opengl;
  CONAN_PKG::glu;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,MODULE_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:>
>;
$<$<CONFIG:RelWithDebInfo>:
  ;
  CONAN_PKG::opengl;
  CONAN_PKG::glu;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,MODULE_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:>
>;
$<$<CONFIG:MinSizeRel>:
  ;
  CONAN_PKG::opengl;
  CONAN_PKG::glu;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,MODULE_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:>
>;
$<$<CONFIG:Debug>:
  CONAN_LIB::glew_glew32ddebug;
  CONAN_PKG::opengl;
  CONAN_PKG::glu;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,SHARED_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,MODULE_LIBRARY>:>;
  $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:>
>

cmake_multi seems to forgo the use of per-configuration properties such as INTERFACE_LINK_LIBRARIES_DEBUG or INTERFACE_LINK_LIBRARIES_RELEASE, preferring to set the config-independent properties and using generator expressions to ensure the correct files are used for each configuration.

The problem is that this only seems to work for the predefined configurations Release, RelWithDebInfo, MinSizeRel, and Debug. When the CMake script or user adds extra configurations, e.g. DebugSpecial, then tries to map that configuration to Debug for imported dependencies via set(CMAKE_MAP_IMPORTED_CONFIG_DEBUGSPECIAL Debug), the library won’t be found: CMake will probably first try looking for the property INTERFACE_LINK_LIBRARIES_DEBUGSPECIAL, find that it doesn’t exist, and based on the defined mapping try to fall back to INTERFACE_LINK_LIBRARIES_DEBUG, which won’t exist either. Lastly, it would fall back to INTERFACE_LINK_LIBRARIES, which unfortunately only contains generator expressions for the predefined configurations.

Is this a known problem ?