I spent a whole week trying to understand a bunch of errors this otherwise awesome tool (i.e. PlatformIO) had been throwing to my face while building multi-targeted project. Finally, I brute-forced that
src_filter is NOT relative to
[project_dir/src], but rather to
[project_dir] itself. Once I figured that out, everything works like a charm.
Is there the mistake in the documentation, or I didn’t get it right?