Highlights

• Lazy propagation
• Lazy requirement validation
• App::write_help takes &mut self now
• App::override_usage No longer implies \t which allows multi lined usages
• In usage parser, for options [name]... --option [val] results in ArgSettings::MultipleOccurrences but --option [val]... results in ArgSettings::MultipleValues and ArgSettings::MultipleOccurrences. Before both resulted in the same thing
• Allow empty values no longer default
• UseValueDelimiter no longer the default
• Multiple delima fixed (vals vs occurrences)
• Ability to mutate args once they've been added to an App
• App::args and App::arg are more generic
• Can unset global settings
• Instead of adding arg with long --help or --version you can use App::mut_arg to override things
  • Caution, must fully override
  • No longer forces auto-handle of help/ver however if still desired AppSettings::NoAuto{Help,Version}

How to Upgrade

If you use Arg::multiple(true)

Deprecations

Simple Renames

App

• App::get_matches_safe -> App::try_get_matches
• App::get_matches_from_safe -> App::try_get_matches_from
• App::get_matches_safe_borrow -> App::try_get_matches_from_mut
• App::usage -> App::override_usage
• App::help -> App::override_help
• App::template -> App::help_template

Arg

• Arg::unset -> Arg::unset_setting
• Arg::set -> Arg::setting

Structural Changes

App

• App::version_message -> App::mut_arg
• App::version_short -> App::mut_arg
• App::help_message -> App::mut_arg
• App::help_short -> App::mut_arg
• App::args_from_usage -> App::args(&str)
• App::arg_from_usage -> App::arg(&str)
• App::write_help -> &self -> &mut self (#808)
• App::gen_completions -> clap_completions::generate
• App::gen_completions_to -> clap_completions::generate_to
• App::settings -> App::setting(Setting1 | Setting2)
• App::unset_settings -> App::unset_setting(Setting1 | Setting2)
• App::global_settings -> App::global_setting(Setting1 | Setting2)

Arg

• Arg::from_usage -> Arg::from(&str)

Additional APIs

App

• App::mut_arg
• App::unset_global_setting

Arg