Function get_root_platformio_build_flags

ci/compiler/build_config.py:33–89

Read the root ``platformio.ini`` and return ``build_flags`` for the matching ``[env: ]`` section, with ``extends`` and ``[env]`` inheritance resolved. This exists to fix issue #2664: ``bash compile --backend platformio`` synthesises a fresh PIO project at ``.build/pio/<en

(board_name: str, project_root: Path)

def get_root_platformio_build_flags(board_name: str, project_root: Path) -> list[str]:
    """Read the root ``platformio.ini`` and return ``build_flags`` for the
    matching ``[env:<board_name>]`` section, with ``extends`` and ``[env]``
    inheritance resolved.

    This exists to fix issue #2664: ``bash compile --backend platformio``
    synthesises a fresh PIO project at ``.build/pio/<env>/platformio.ini``
    from ``ci/boards.py`` and was silently discarding ``build_flags`` defined
    in the user&#x27;s root ``platformio.ini``. Anyone editing the root file
    reasonably expects those flags to take effect; without this merge step
    they vanish, producing subtle "flags work under fbuild but not under
    --backend=platformio" bugs.

    Behaviour:
    - Returns an empty list if the root ``platformio.ini`` is missing,
      malformed, or has no matching ``[env:<board_name>]`` section.
    - Substitution variables like ``${env:generic-esp.build_flags}`` and
      ``extends = env:generic-esp`` are resolved using the existing
      :class:`PlatformIOIni` parser, which already implements PlatformIO&#x27;s
      inheritance semantics.
    - Never raises: parse errors are swallowed and logged so that a broken
      root file cannot block a build.

    Args:
        board_name: The PlatformIO env name (e.g. ``"esp32c6"``). Matches
            ``[env:<board_name>]`` in the root ini.
        project_root: FastLED project root containing ``platformio.ini``.

    Returns:
        Ordered list of build_flags strings, or ``[]`` when nothing applies.
    """
    root_ini = project_root / "platformio.ini"
    if not root_ini.exists():
        return []

    try:
        # Local import to avoid a circular import at module load.
        from ci.compiler.platformio_ini import PlatformIOIni

        pio_ini = PlatformIOIni.parseFile(root_ini)
        parsed = pio_ini.parsed
        env = parsed.environments.get(board_name)
        if env is None:
            return []
        # `parsed` already has extends + [env] inheritance applied, and
        # ${env:...} substitutions resolved (see _resolve_list_variables in
        # ci/compiler/platformio_ini.py).
        return list(env.build_flags)
    except KeyboardInterrupt as ki:
        handle_keyboard_interrupt(ki)
        raise
    except Exception as e:
        # Never let a malformed root platformio.ini block a build.
        print(
            f"Warning: failed to read root platformio.ini for env '{board_name}': {e}"
        )
        return []