pw_build/merge_flags.bzl

# Copyright 2024 The Pigweed Authors
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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"""Functions for merging flags for platforms and transitions."""

def flags_from_dict(flags_dict):
    """Convert a dict of flags into a list.

    Args:
      flags_dict: Dict mapping flag labels to values.

    Returns:
       A list of flags in a format accepted by the `flags` attribute of `platform`.
    """
    return ["--{}={}".format(k, v) for k, v in flags_dict.items()]

def merge_flags(base, override):
    """Merge flags for platforms.

    See https://pigweed.dev/bazel_compatibility.html#provide-default-backend-collections-as-dicts
    for a usage example.

    Args:
       base: Dict of flags to use as the starting point. Typically one of
          the dictionaries provided in @pigweed//pw_build:backends.bzl.
       override: Dict of overrides or additions to the base dict.

    Returns:
       A list of flags in a format accepted by the `flags` attribute of `platform`.
    """
    return flags_from_dict(base | override)

def merge_flags_for_transition_impl(base, override):
    """Merge flags for a transition's impl function.

    Args:
       base: Dict of flags to use as the starting point. Typically one of
          the dictionaries provided in @pigweed//pw_build:backends.bzl.
       override: Dict of overrides or additions to the base dict.
    """
    return base | override

def merge_flags_for_transition_outputs(base, override):
    """Merge flags for a transition's output function.

    Args:
       base: Dict of flags to use as the starting point. Typically one of
          the dictionaries provided in @pigweed//pw_build:backends.bzl.
       override: Dict of overrides or additions to the base dict.
    """
    return (base | override).keys()