CMake variants, Cartesian but only for certain builds

[savvn001]

Hi,

I've been wondering if it's possible to configure the cmake-variants.yaml such that, some of the options only apply to certain other options. Or in other words, some options are excluded from others, so the combinations listed aren't a full cartesian product.

Take the example below:

buildType:
  default: debug
  description: Select build type
  choices:
    debug:
      short: Debug Firmware
      long: Debug config, logs on and debug info generated
      buildType: DEBUG
    release:
      short: Release Firmware
      long: Relase build, logs off, max optimization
      buildType: RELEASE
    test_host:
      short: Test Host
      long: Config for building unit tests on host machine
      buildType: CTEST
    test_device:
      short: Test Device
      long: Config for building unit tests for target device
      buildType: TEST_DEVICE

CLI_LOGs:
  default: cli_logs
  choices:
    cli_logs:
      short: CLI ON, LOGS ON
      long: CLI ON, logs ON
      settings:
        CLI: true
        LOGS: true
    log_only:
      short: CLI OFF, LOGS ON
      long: CLI OFF, logs ON
      settings:
        CLI: false
        LOGS: true
    none:
      short: CLI OFF, LOGS OFF
      long: CLI OFF, logs OFF
      settings:
        CLI: false
        LOGS: false

SOFTDEVICE:
  default: on
  choices:
    on:
      short: Softdevice ON
      settings:
        SOFTDEVICE: true
    off:
      short: Softdevice OFF
      settings:
        SOFTDEVICE: false

BOARD:
  default: V1
  choices:
    V1:
      short: V1 Board
      settings:
        BOARD: V1
    V2:
      short: V2 Board
      settings:
        BOARD: V2  

In my example, you can see the first option is 4 different build profiles, I switch between them, and it tells CMake which toolchain and optimisation to use etc. Now, the issue is, I want the CLI_LOGs, SOFTDEVICE, BOARD options to only be applied to the debug and release build options. So in essence, the options listed are not a full cartesian product.

Is this possible? Or am I thinking about it completely wrong and need to approach it differently? I really like the idea of variants as it allows me to easily flick between different build configurations. But in this particular situation, I need it to not quite be a full matrix combination.

[bobbrow]

Unfortunately, there is not a way to set up rules for custom combinations when using variants. If you'd like to have more control over this. you'd have to switch to using CMakePresets.json. Though CMake presets don't let you specify rules either, you can define presets that consist of a combination of other partial presets such that you could get what you want.

It's on our backlog to come up with a proposal to Kitware that will allow for easier combinatorics with CMake presets. (e.g. address this: https://gitlab.kitware.com/cmake/cmake/-/issues/22538)

[savvn001]

Ah thanks, sure. For now I've just manually made the combinatorics so that it's exactly how I want. It's not scalable but works for now since I don't have a large amount of combinations. I'll probably as a workaround make a simple script to generate a cmake-variants.yaml file in the future with the exact combos I need as the project grows.