Zephyr external modules cannot be placed inside zephyr directory

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[x] PlatformIO Core. If you’ve found a bug, please provide an information below.

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Configuration

Operating system: Mac OS 10.15.5

PlatformIO Version (platformio --version): 4.3.4

Description of problem

This is a problem with the zephyr framework integration. I am developing a custom device driver and I don't want to put it inside zephyr tree. I go with external modules as described here and here. I put the module source inside zephyr directory, but the compilation error unable to find the source files.

Steps to Reproduce

Create a module directory inside zephyr dir (alongside with the CMakeLists.txt and prj.conf)

Structure the module directory as described here

zephyr
_drivers
__m24m02
___ zephyr
____CMakeLists.txt
____Kconfig
____m24m02.c

list(APPEND ZEPHYR_EXTRA_MODULES
${CMAKE_CURRENT_SOURCE_DIR}/drivers/m24m02
)

Enable the module as the registered Kconfig entry in step 2 by modifying zephyr/prj.conf
```
CONFIG_M24M02=y
```

Actual Results

*** [.pio/build/solemetrix_dwm1001/………solemetrix-repo__gms-firmware__zephyr__drivers__m24m02__zephyr/modules/m24m02/m24m02.c.o] Source src/drivers/m24m02/zephyr/m24m02.c' not found, needed by target .pio/build/solemetrix_dwm1001/……__…__solemetrix-repo__gms-firmware__zephyr__drivers__m24m02__zephyr/modules/m24m02/m24m02.c.o’.

Expected Results

Build successfully

If problems with PlatformIO Build System:

The content of platformio.ini:

[env:solemetrix_dwm1001]
platform = nordicnrf52
board = solemetrix_dwm1001
framework = zephyr
monitor_speed = 11520

Additional info

I replicated the the project structure and managed to compile it using west build. Please kindly advise to get it working in platformio.

Solution

It turned out that the source cannot be placed inside the zephyr directory. I created an additional directory in the root platformio project and moved the module source there.

zephyr
zephyr_ext
_drivers
__m24m02
___ zephyr
____CMakeLists.txt
____Kconfig
____m24m02.c

Suggestion

If this is a limitation, please update the documentation. Otherwise, please fix the bug. Thank you.

platformio / zephyr