Fix handling of complex extends in platformio.ini

[kad]

Description

This is minor follow-up for PR #21068.

This PR fixes corner case when custom PlatformIO env section is referencing
a non-env section via 'extends' directive. In that case PlatformIO Config APIs will return single string instead of array, which needs to be handled differently.

It also fixes some of the Python formatting conventions (tabs vs spaces mix in single file).

Requirements

Benefits

Fixes corner case for advanced users.

Configurations

example platformio.ini:

[melzi_custom_flags]
extends = env:melzi
build_flags = ${env:melzi.build_flags} -ffast-math

[env:my_custom_build_env]
extends = melzi_custom_flags
extra_scripts  = pre:buildroot/share/PlatformIO/scripts/custom_pre_hook.py
                 ${melzi_custom_flags.extra_scripts}

Related Issues