How to add CMake config to build tree - cmake

Question

I have a shared library in my project with a cmake config file. How can I make it available in the build tree such that I don't have to install it before using find_package?

Answer 1

The mechanism I was looking for is export(PACKAGE <PackageName>). Note that since 3.15 the command does nothing by default because populating the user package registry has effects outside the source and build trees. You have to set the CMAKE_EXPORT_PACKAGE_REGISTRY variable to add build directories to the CMake user package registry.
I was able to get things working like this:
install(
TARGETS ${TARGET_LIB}
EXPORT TARGET_LIB_EXPORTS # Define exports
FILE "${PROJECT_NAME}-targets.cmake"
…
)
# Create targets file in build tree
export(
EXPORT TARGET_LIB_EXPORTS
FILE "${PROJECT_BINARY_DIR}/${PROJECT_NAME}-targets.cmake"
NAMESPACE ${PROJECT_NAME}::
)
# Create config file in build tree
configure_package_config_file(
"${PROJECT_SOURCE_DIR}/cmake/${PROJECT_NAME}-config.cmake.in"
"${PROJECT_BINARY_DIR}/${PROJECT_NAME}-config.cmake"
INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}-${PROJECT_VERSION}
)
# Create version config file in build tree
write_basic_package_version_file(
"${PROJECT_NAME}-config-version.cmake"
VERSION ${PROJECT_VERSION}
COMPATIBILITY SameMajorVersion
)
# Export the package to make find_package work in build
set(CMAKE_EXPORT_PACKAGE_REGISTRY true)
export(PACKAGE ${PROJECT_NAME})
A basic config file would look like this:
#PACKAGE_INIT#
include("${CMAKE_CURRENT_LIST_DIR}/#PROJECT_NAME#-targets.cmake")