scripts/shac/enforce_bazel_build_file.star

# Copyright 2026 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

def enforce_bazel_build_file(ctx):
    """Checks that a BUILD.bazel file exists when a new FIDL library is created."""

    # Check when :
    # 1. The file is a new BUILD.gn file added under //sdk/fidl/.
    # 2. The BUILD.gn file contains at least one fidl() template.
    for path, meta in ctx.scm.affected_files(glob = "BUILD.gn").items():
        if meta.action != "A":
            continue

        # TODO(https://fxbug.dev/487883318): Extend the check to FIDL libraries outside //sdk/fidl directory.
        if not path.startswith("sdk/fidl/"):
            continue

        # Read the BUILD.gn content
        content = str(ctx.io.read_file(ctx.scm.root + "/" + path))

        # Check if it contains at least one fidl() template
        has_fidl = False
        for line in content.splitlines():
            # Ignore comments
            hash_idx = line.find("#")
            if hash_idx != -1:
                line_code = line[:hash_idx]
            else:
                line_code = line
            if ctx.re.allmatches(r"\bfidl\s*\(\s*[\"\']", line_code):
                has_fidl = True
                break

        # Skip if the BUILD.gn file doesn't contain any fidl() template
        if not has_fidl:
            continue

        # Check if BUILD.bazel exists in the same directory
        bazel_path = "/".join(path.split("/")[:-1] + ["BUILD.bazel"])

        if not ctx.scm.all_files(glob = bazel_path):
            ctx.emit.finding(
                level = "error",
                filepath = path,
                message = "BUILD.bazel file is missing in the same directory as the added FIDL BUILD.gn file.",
            )

def register_bazel_build_file_checks():
    shac.register_check(shac.check(enforce_bazel_build_file))