All TypeScript CLI scripts in tools/ and packages/*/scripts/ follow a consistent pattern:

packages/*/scripts/ should be its own Bazel package with a local BUILD.bazel. Keep build-time parsers, generators, and their tests in that package instead of adding script sources or parser tests to the parent package runtime/test target.

For example, packages/intl-collator/scripts:parsers owns the UCA and LDML parser sources, and packages/intl-collator/scripts:parsers_test owns their unit tests. The parent //packages/intl-collator:intl-collator_test target should cover runtime package behavior and should not depend on script parser sources just to make parser tests pass.

When a script parses XML, use a real XML parser such as fast-xml-parser as a build-time/dev dependency. Do not parse XML with tag/attribute regexes. Regexes that remain for non-XML grammars should be hoisted to module-level constants so hot parser paths do not recreate them.

Define an Args interface extending minimist.ParsedArgs with typed fields for all CLI arguments:

import minimist from 'minimist'

interface Args extends minimist.ParsedArgs {
  out: string
  format?: string
  external?: string | string[] // use union for --flag that can repeat
}

Extract logic into a main(args: Args) function:

function main(args: Args) {
  const {out, format} = args
  // ...
}

Use async function main(args: Args) if the script uses await.

Use import.meta.filename to guard the entry point:

if (import.meta.filename === process.argv[1]) {
  main(minimist<Args>(process.argv.slice(2)))
}

For CLI flags that can repeat (e.g., --external foo --external bar), use [].concat(args.flag || []) to normalize:

const externals: string[] = [].concat(args.external || [])

See tools/generate-supported-locales.ts for the canonical minimal example, or tools/rolldown-bundle.ts for a more complex one.