async function generateBazelWorkspace()

in internal/npm_install/generate_build_file.ts [469:537]
63 lines of code
10 McCabe index (conditional complexity)

async function generateBazelWorkspace(pkg: Dep, workspace: string) {
  let bzlFile = `# Generated by the yarn_install/npm_install rule
load("@bazel_tools//tools/build_defs/repo:utils.bzl", "maybe")
load("@build_bazel_rules_nodejs//internal/copy_repository:copy_repository.bzl", "copy_repository")

`;

  const rootPath = pkg.bazelWorkspaces[workspace].rootPath;
  if (!rootPath) {
    console.error(
        `Malformed bazelWorkspaces attribute in ${pkg._dir}@${pkg.version}. ` +
        `Missing rootPath for workspace ${workspace}.`);
    process.exit(1);
  }

  // Copy all files for this workspace to a folder under _workspaces
  // to restore the Bazel files which have be renamed from the npm package
  const workspaceSourcePath = path.posix.join('_workspaces', workspace);
  const nodeModules = nodeModulesFolder();
  await mkdirp(workspaceSourcePath);
  await Promise.all(pkg._files.map(async (file) => {
    if (/^node_modules[/\\]/.test(file)) {
      // don't copy over nested node_modules
      return;
    }
    let destFile = path.relative(rootPath, file);
    if (destFile.startsWith('..')) {
      // this file is not under the rootPath
      return;
    }
    const basename = path.basename(file);
    const basenameUc = basename.toUpperCase();
    // Bazel BUILD files from npm distribution of rules_nodejs 1.x
    // would have been renamed before publishing with a _ prefix so
    // we restore the name on the copy
    if (basenameUc === '_BUILD' || basenameUc === '_BUILD.BAZEL') {
      destFile = path.posix.join(path.dirname(destFile), basename.substr(1));
    }
    const src = path.posix.join(nodeModules, pkg._dir, file);
    const dest = path.posix.join(workspaceSourcePath, destFile);
    await mkdirp(path.dirname(dest));
    await fs.copyFile(src, dest);
  }));

  // We create _bazel_workspace_marker that is used by the custom copy_repository
  // rule to resolve the path to the repository source root. A root BUILD file
  // is required to reference _bazel_workspace_marker as a target so we also create
  // an empty one if one does not exist.
  if (!hasRootBuildFile(pkg, rootPath)) {
    await writeFile(
        path.posix.join(workspaceSourcePath, 'BUILD.bazel'),
        '# Marker file that this directory is a bazel package');
  }
  const sha256sum = crypto.createHash('sha256');
  sha256sum.update(await fs.readFile(config.package_lock, {encoding: 'utf8'}));
  await writeFile(
      path.posix.join(workspaceSourcePath, '_bazel_workspace_marker'),
      `# Marker file to used by custom copy_repository rule\n${sha256sum.digest('hex')}`);

  bzlFile += `def install_${workspace}():
    maybe(
        copy_repository,
        name = "${workspace}",
        marker_file = "@${config.workspace}//_workspaces/${workspace}:_bazel_workspace_marker",
    )
`;

  await writeFile(`install_${workspace}.bzl`, bzlFile);
}