Have CMake execute a file which is not CMakeLists.txt - cmake

Question

Is that true that you can't customize the name of your CMakeLists.txt file? I read in a few places that make suffers from the same problem, but that's completely not true, you sure can:
~$ make -f whatever_name_you_feel_like
Can't you do this with CMake?
My situation is as follows: The project leader wants to have a certain CMakeLists.txt file run in the CI workflow and another when developing. I thought it would be possible to just keep 2 CMake files and tell cmake which one to execute.

Answer 1

It's not possible to use file with a name different to CMakeLists.txt, but I'm almost certain that's not actually what you want to do anyways.
I assume the cl version and the development version are mostly similar and only some details change. In this case you should not duplicate the logic. Instead add one or multiple options to your cmake project that can set when you set up the build dir and can even be changed without reconfiguring the whole project from scratch. Basically you add a cache variable to CMakeLists.txt which allows the user to overwrite the default value via -D command line option. The value can also be modified after the initial configuration using cmake-gui.
cmake_mimimum_required(VERSION 3.0.2)
project(MyProject)
# option set to true by default
set(MY_PROJECT_COMMAND_LINE_BUILD 1 CACHE BOOL "Use the command line configuration for MyProject")
#logic common to both configurations
add_executable(MyProg foo.cpp bar.cpp)
if(MY_PROJECT_COMMAND_LINE_BUILD)
#logic only for command line build
target_compile_definitions(MyProg PRIVATE COMMAND_LINE_BUILD)
else()
# logic only for non-command line build
target_compile_definitions(MyProg PRIVATE DEVELOPMENT_BUILD)
endif()
Ironically you could set up both from the command line:
Command line build
cmake -S sourceDir -B buildDir
Development build
cmake -D MY_PROJECT_COMMAND_LINE_BUILD:BOOL=0 -S sourceDir -B buildDir
If you don't want to enter the cache values in the command line every time you set up the project, you could also use a cmake script file to initialize the cache values using the -C command line option.
cmake -C developmentVersion.cmake -S sourceDir -B buildDir
developmentVersion.cmake:
set(MY_PROJECT_COMMAND_LINE_BUILD 0 CACHE BOOL "Use the command line configuration for MyProject")
Theoretically you could the whole CMakeLists.txt file in an if else endif structure and use include in one of the alternatives to competely replace the standard logic in the CMakeLists.txt file, but imho this is not a good idea.

Answer 2

Can't you do this with CMake?
No, it's not possible.
The project leader wants to have a certain CMakeLists.txt file run in the CI workflow and another when developing.
One way: copy or symlink proper CMakeLists.txt before executing cmake.
Preferably one would use cmake scripting language:
# CMakeLists.txt
if (MODE STREUQAL "CI_WORKFLOW")
include(CMakeLists-ci-workflow.txt)
elseif (MODE STREQUAL "DEVELOPING")
include(CMakeLists-developing.txt)
else()
message("SUPER ERROR")
fi()
and then separate CMakeLists-ci-workflow.txt and separate CMakeLists-developing.txt and do cmake -D MODE=DEVELOPING or -D MODE=CI_WORKFLOW.
But overall, the idea of "separate CMakeLists.txt" sounds bad to me. Instead use CMAKE_BUILD_TYPE=Debug for developing and CMAKE_BUILD_TYPE=Release for release builds, and use other cmake variables to differentiate settings, instead of duplicating configuration.