CMake - Pass a list as a string to add_custom_target for CMake script

add_custom_target seems to be 'unpacking' lists when I don't want it to. Take this add_custom_target that I'm using to invoke a CMake script:

message(STATUS "Sources: ${ARGS_SOURCES}")
add_custom_target(${ARGS_TARGET}
    COMMAND ${CMAKE_COMMAND}
            -DSOURCES="${ARGS_SOURCES}"
            -DOUTPUT_DIR="${ARGS_OUTPUT_DIR}"
            -P "${CMAKE_SOURCE_DIR}/cmake/translation_generator/translation_generator_script.cmake"
    SOURCES ${ARGS_SOURCES}
            "${CMAKE_SOURCE_DIR}/cmake/translation_generator/translation_generator_script.cmake")

The message output is what I'm expecting, a list of paths separated by semi-colons.

-- Sources: /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/en_GB.toml;/home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/fr.toml;/home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/ja.toml

However when the script is invoked, I get this:

/usr/bin/cmake -DSOURCES="/home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/en_GB.toml /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/fr.toml /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/ja.toml" ...

It's unpacked the list into a space separated string - this is not what I want.

I attempted to use the VERBATIM flag but it completely mangled the invocation:

/usr/bin/cmake -DSOURCES=\"/home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/en_GB.toml /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/fr.toml /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/ja.toml\" ...

It's escaping the double quotes. If I remove them:

/usr/bin/cmake -DSOURCES=/home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/en_GB.toml /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/fr.toml /home/cmannett85/workspace/arg_router/examples/resources/simple_ml_gen/ja.toml ...

It keeps the spaces, breaking the called script. I also tried:

list(JOIN ARGS_SOURCES ";" ARGS_SOURCES)

But the unpacking appears to happen in the add_custom_target processing, so this made no difference.

So my question is: How do I pass a list to a add_custom_target command, as a semi-colon separated string?

CMake quoting is confusing. For example: "this" is quoted. For example: th"is" is not quoted, and " are taken literally.

In your example, -DSOURCES="${ARGS_SOURCES}" " are literal. So ARGS_SOURCES is split, as it is an array, and your program receives multiple arguments like '-DSOURCES="elem1' 'elem2' 'elem3' 'elem4"' with the " quotes.

If you want to quote in CMake, the first character has to be " and the last character has to be ". Just like you did with "Sources: ${ARGS_SOURCES}".

"-DSOURCES=${ARGS_SOURCES}"