Build Mbed application with out-of-tree modules

[ATmobica]

Is your feature request related to a problem? Please describe.
My Mbed project has a specific source tree:

mbed_app/
├─ mbed_app.json
third_party/
├─ wifi_lib/
│ ├─ mbed_lib.json

I want to build a Mbed application with out-of-tree WiFi module (Mbed OS compatible wifi-ism43362 ) but I do not see the possibility of indicating the path to it and join the configuration from mbed_lib.json.
Now, the only option is to move wifi_lib to mbed_project directory (create a symlink for example) and I would like to avoid it.

Describe the solution you'd like
Added option to include .json out-of-tree configuration file when generating mbed config.cmake. For example, this could be a new argument to the mbed-tools configure command.

[LDong-Arm]

Hi @ATmobica, building out-of-tree modules should be possible. This is controlled by CMake instead of mbed-tools.

Could you try adding the following to mbed_app/CMakeLists.txt:

add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/../third_party/wifi_lib wifi_lib_build)

? Note that the second argument of add_subdirectory() (in our case wifi_lib_build) is needed when including an out-of-tree module, but it can be named anything.

[ATmobica]

@LDong-Arm Yes, the building works but the propagation settings from mbed_lib.json file does not.
To build wifi_lib I need some compilation flags which should be created by

mbed-tools configure in mbed_config.cmake file.

But I couldn't pass the path to mbed_lib.json file to it.

[LDong-Arm]

@LDong-Arm Yes, the building works but the propagation settings from mbed_lib.json file does not.

This is a good point.

The idea behind automatically scanning mbed_lib.json under the current project comes from the old Mbed CLI tools (i.e. mbed compile, before the time of mbed-tools compile) where configuration files are automatically scanned. Whenever scanning is involved, it's hard to look outside the current source tree. For now we have mbed_lib.json (and thus, scanning) for backward compatibility with the old tools, so such limitation exists.

Describe the solution you'd like
Added option to include .json out-of-tree configuration file when generating mbed config.cmake. For example, this could be a new argument to the mbed-tools configure command.

@ARMmbed/mbed-os-core What do you think of @ATmobica's suggestion?

[ATmobica]

@LDong-Arm Hi, is there any progress or decisions on this issue?