rules/directory/subdirectory.bzl

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#
# 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
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
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"""Skylib module containing rules to create metadata about subdirectories."""

load(":providers.bzl", "DirectoryInfo")

def _subdirectory_impl(ctx):
    dir = ctx.attr.parent[DirectoryInfo].get_subdirectory(ctx.attr.path)
    return [
        dir,
        DefaultInfo(files = dir.transitive_files),
    ]

subdirectory = rule(
    implementation = _subdirectory_impl,
    attrs = {
        "parent": attr.label(
            providers = [DirectoryInfo],
            mandatory = True,
            doc = "A label corresponding to the parent directory (or subdirectory).",
        ),
        "path": attr.string(
            mandatory = True,
            doc = "A path within the parent directory (eg. \"path/to/subdir\")",
        ),
    },
    provides = [DirectoryInfo],
)