Multi tool use

How do I detect whether include(SomeModule) will work?

I'm using a library which may or may not export SomeModule.cmake. If it exists, I want to use it for its better capabilities, but otherwise, I want to use a simple workaround.

However, if include(SomeModule) fails, CMake fails immediately with the message:

include(SomeModule)

CMake Error at CMakeLists.txt:42 (include):
include could not find load file:

SomeModule


How do I detect whether include(SomeModule) will work without manually intervening?

include(SomeModule)

I'm picturing something like this:

# this function doesn't exist:
detect_include_exists(SomeModule)

if(SomeModule_FILE_EXISTS)
include(SomeModule)

# call the functions inside of SomeModule
else()
# workaround code
endif()


2 Answers
2

Command include support OPTIONAL argument for ignore absent files. Using it with RESULT_VARIABLE you may check whether include() has actually included the file or not:

include()

include(SomeModule OPTIONAL RESULT_VARIABLE SomeModule_Found)
if(NOT SomeModule_Found)
# Include file is absent. Need some workaround.
endif()


include

We can use find_file in combination with CMAKE_MODULE_PATH for this:

find_file

CMAKE_MODULE_PATH

find_file(SomeModule_FILE SomeModule.cmake
PATHS ${CMAKE_MODULE_PATH}
)
# potentially:
# mark_as_advanced(SomeModule_FILE)

if(SomeModule_FILE)
include("${SomeModule_FILE}")

# call the functions inside of SomeModule
else()
# workaround code
endif()


The search isn't strictly equivalent to the one which include(SomeModule) would perform, but it's close enough for many purposes.

include(SomeModule)

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