Do generators expression work with BASE_DIRS in target_sources

Usage
1

I can post a longer example of this issue if needed but I wanted to see if what I am doing is just not expected to work. I have a CMakeLists.txt like

target_sources(HelloWorld PUBLIC 
   FILE_SET generated_export_headers 
   TYPE HEADERS
   BASE_DIRS 
        $<BUILD_INTERFACE:${CMAKE_BINARY_DIR}/HelloWorld> 
        $<INSTALL_INTERFACE:${CMAKE_BINARY_DIR}>
   FILES ${CMAKE_BINARY_DIR}/HelloWorld/helloworld_export.h)

When I use this it seems whatever I do the BUILD_INTERFACE is used in the install step. That is the install happens in the root install include directory never in a subdirectory called “HelloWorld” which is what I would have expected.

I assume I am doing something very dumb but in my defense BASE_DIRS is barley documented at all.

So should I expect generator expressions to work in BASE_DIRS?

2

I don’t think it makes sense to have separate build/install interfaces for BASE_DIRS. What is the goal here? To require helloworld_export.h when including in the source tree, but HelloWorld/helloworld_export.h when it is installed? Given that the header is meant to be included by public headers, how are both spellings going to be satisfied by the files that include it?