@rule(level=LogLevel.DEBUG)
async def download_external_tool(request: ExternalToolRequest) -> DownloadedExternalTool:
    # Download and extract.
    maybe_archive_digest = await Get(Digest, DownloadFile, request.download_file_request)
    extracted_archive = await Get(ExtractedArchive, Digest, maybe_archive_digest)

    # Confirm executable.
    exe_path = request.exe.lstrip("./")
    digest = extracted_archive.digest
    is_not_executable = False
    digest_entries = []
    for entry in await Get(DigestEntries, Digest, digest):
        if isinstance(entry, FileEntry) and entry.path == exe_path and not entry.is_executable:
            # We should recreate the digest with the executable bit set.
            is_not_executable = True
            entry = dataclasses.replace(entry, is_executable=True)
        digest_entries.append(entry)
    if is_not_executable:
        digest = await Get(Digest, CreateDigest(digest_entries))

    return DownloadedExternalTool(digest, request.exe)