Mapping lists in generator expressions

Usage
1

I would like to write a generator expression which takes a list of targets, and retrieves a target property for each one producing a list of values.

Is there a way to do this? I can’t see an obvious way.

I thought of one very tricky way to do this using $<GENEX_EVAL:expr>:

$<GENEX_EVAL:$<LIST:TRANSFORM,${targets},REPLACE,(.+),$<DOLLAR>$<ANGLE-L>TARGET_PROPERTY:\\1$<COMMA>${prop}$<ANGLE-R>>>

…except it doesn’t work because there are no $<DOLLAR> and $<ANGLE-L> expressions, so how can I escape the inner expression?

2

Do things work if you replace $<DOLLAR> with $<1:$>, or $<ANGLE-L> with $<1:<>? I think the latter might be a bit problematic, but the former might work.

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3

Ok, that works! Thank you. It even works recursively!:

set(targets picolibc::picolibc ZLIB::ZLIB)

function(escape_generator_expression var)
    string(REPLACE ">" "__ANGLE_R__" ${var} "${${var}}")
    string(REPLACE "$" "$<1:$>" ${var} "${${var}}")
    string(REPLACE "," "$<COMMA>" ${var} "${${var}}")
    string(REPLACE "__ANGLE_R__" "$<ANGLE-R>" ${var} "${${var}}")
    return(PROPAGATE ${var})
endfunction()

set(prop "INTERFACE_INCLUDE_DIRECTORIES")
set(get_prop "$<TARGET_PROPERTY:\\1,${prop}>")
escape_generator_expression(get_prop)
escape_generator_expression(get_prop)

set(expr "$<GENEX_EVAL:$<GENEX_EVAL:$<LIST:TRANSFORM,${targets},REPLACE,(.+),${get_prop}>>>")
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