PackageProject: Does not work if more than one TARGET is used

[jenisys]

VERIFIED WITH VERSION: 1.11.2 (using cmake version 3.27.5 and 3.30.2)

• I added a second library to the ModernCppStarter/CMakeLists.txt file
• When I perform "cmake init" to create the build directory,
  the second library is missing in the exported-cmake-targets file.

How to Repeat

STEPS:

• Clone the ModernCppStarter repo and change into the "ModernCppStarter" subdirectory
• MAYBE OPTIONAL: In CMakeLists.txt file,
  change the line CPMAddPackage("gh:TheLartians/PackageProject.cmake@1.8.0") to use version 1.11.2.
• Add a second library to the ModernCppStarter/CMakeLists.txt file:

# -- TASK: Add a SECOND LIBRARY to the "ModernCppStarter/CMakeLists.txt" file after the first library
# SEE: https://github.com/TheLartians/ModernCppStarter/blob/master/CMakeLists.txt
...
add_library(Hello)
add_library(${PROJECT_NAME}::Hello ALIAS Hello)
target_sources(Hello
    PUBLIC ${headers}
    PUBLIC ${sources}
)
set_target_properties(Hello PROPERTIES CXX_STANDARD 20)
target_link_libraries(Hello PRIVATE fmt::fmt)
target_include_directories(Hello PUBLIC
    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
    $<INSTALL_INTERFACE:include/${PROJECT_NAME}-${PROJECT_VERSION}>
)
...

• In a bash shell: Perform cmake-init to create and populate the "build" directory:

$ cmake -B build -S .
-- The CXX compiler identification is GNU 11.4.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- CPM: Adding package PackageProject.cmake@1.11.2 (v1.11.2)
-- CPM: Adding package fmt@10.2.1 (10.2.1)
-- Version: 10.2.1
-- Build type:
-- Configuring done (5.7s)
-- Generating done (0.0s)
-- Build files have been written to: xxx/TheLartians_ModernCppStarter/build 

$ cd build
$ grep -R Greeter::
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets-noconfig.cmake:# Import target "Greeter::Greeter" for configuration ""
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets-noconfig.cmake:set_property(TARGET Greeter::Greeter APPEND PROPERTY IMPORTED_CONFIGURATIONS NOCONFIG)
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets-noconfig.cmake:set_target_properties(Greeter::Greeter PROPERTIES
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets-noconfig.cmake:list(APPEND _cmake_import_check_targets Greeter::Greeter )
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets-noconfig.cmake:list(APPEND _cmake_import_check_files_for_Greeter::Greeter "${_IMPORT_PREFIX}/lib/Greeter-1.0/libGreeter.a" )
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets.cmake:foreach(_cmake_expected_target IN ITEMS Greeter::Greeter)
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets.cmake:# Create imported target Greeter::Greeter
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets.cmake:add_library(Greeter::Greeter STATIC IMPORTED)
CMakeFiles/Export/062d20113924c92337e05e6db16f7bdf/GreeterTargets.cmake:set_target_properties(Greeter::Greeter PROPERTIES

PROBLEM

• The second library Hello/Greeter::Hello (as TARGET) is not contained the ${THIS_PROJECT}-exported-cmake-targets file (aka: build/CMakeFiles/Export/${THIS_PROJECT}Targets*.cmake)
• Therefore, you cannot find the second library with find_package() as CMake command.

EXPECTED

• Second library is contained in exported-cmake-targets file for ${THIS_PROJECT}
• Additional targets should be contained, too (if any additional TARGETS/ARTIFACTS are defined).
• BETTER: Provide an optional-parameter in packageProject that allows to specify the TARGETS/EXPORTED_TARGETS (if the TARGETS cannot be auto-discovery in the namespace ${PROJECT_NAME}.

QUESTION

• Am I missing something here ?!?
• I found no constraint in the description of the project
  that PackageProject() only works if only one TARGET (executable or library) is defined.
• I looked at the implementation of packageProject() and see that only one TARGET is processed internally.

[Krzmbrzl]

This will be fixed by #48, if you agree with the sentiment that your library/project having multiple targets is semantically identical to your library/project having multiple components.