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migrate_v1_to_v2.md

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Migration from v1 to v2

In short:

  • Fix all deprecation warnings.
  • If you extended argparse classes - propagate appropriate changes.

1. Change all options, method and action names from camelCase to snake_case.

For example:

  • argparse.ArgumentParser({ addHelp: false }) -> argparse.ArgumentParser({ add_help: false })
  • parser.printHelp() -> parser.print_help()
  • parser.add_argument({ action: 'storeTrue' }) -> parser.add_argument({ action: 'store_true' })

Old names still have aliases (with deprecation messages), and your code may work. But no guarantees, especially if you extend classes.

2. defaultValue => default, constValue => const.

Old names still has aliases with deprecaion messages, to simplify migration.

3. In add_argument, argument names should be raw params (not array).

parser.add_argument('-h', '--help', { help: 'show this help message and exit' })

Old signature is supported but shows deprecation message.

4. debug option of argparse.ArgumentParser is deprecated

Override .exit() method instead.

const argparse = require('argparse')

class MyArgumentParser extends argparse.ArgumentParser {
  exit() { console.log('no exiting today') }
}

parser = new MyArgumentParser()

5. version option of argparse.ArgumentParser is deprecated

Use version action instead:

parser.add_argument('-v', '--version', { action: 'version', version: '1.0.0' })

6. string type is renamed to str

parser.add_argument('--foo', { type: 'str' })

Old signature is supported but shows deprecation message.

7. Only TypeErrors are intercepted from type functions

If user input is invalid, throw TypeError instead of Error:

parser.add_argument('--digit', {
  type: function digit(v) {
    if (!/^\d$/.test(v)) throw TypeError('not a digit')
    return +v
  }
})

TypeErrors will get intercepted and turned into user-friendly error messages, but ordinary Errors will not.

8. constants are moved to top-level

Constants SUPPRESS, OPTIONAL, ZERO_OR_MORE, ONE_OR_MORE, PARSER, and REMAINDER previously available as argparse.Const.* are renamed to argparse.*.

Constant _UNRECOGNIZED_ARGS_ATTR is no longer exposed publicly.

Constant EOL no longer exists (hardcoded as '\n') - replace with '\n' if you used it somewhere.

9. namespace methods .isset, .set, .get, .unset are removed

Get values from Namespace as if it was a plain js object.

10. an absense of value is indicated by undefined instead of null

  • if you passed null to any of the functions, it will be treated as a value (not replaced by default)
  • parse_args will return { x: undefined } instead of { x: null } if optional arg isn't specified