MagicalMethods

They are the reason why structopt is so easy to use and convenient in most cases. Many of them have defaults, some of them get used even if not mentioned.

Methods may be used on "top level" (on top of a struct, enum or enum variant) and/or on "field-level" (on top of a struct field or inside of an enum variant). Top level (non-magical) methods correspond to App::method calls, field-level methods are Arg::method calls.

#[structopt(top_level)]
struct Foo {
    #[structopt(field_level)]
    field: u32
}

#[structopt(top_level)]
enum Bar {
    #[structopt(top_level)]
    Pineapple {
        #[structopt(field_level)]
        chocolate: String
    },

    #[structopt(top_level)]
    Orange,
}

  • name: [name = "name"]

    • On top level: App::new("name").

      The binary name displayed in help messages. Defaults to the crate name given by Cargo.

    • On field-level: Arg::with_name("name").

      The name for the argument the field stands for, this name appears in help messages. Defaults to a name, deduced from a field, see also rename_all.

  • version: [version = "version"]

    Usable only on top level: App::version("version" or env!(CARGO_PKG_VERSION)).

    The version displayed in help messages. Defaults to the crate version given by Cargo. If CARGO_PKG_VERSION is not set no .version() calls will be generated unless requested.

  • no_version: no_version

    Usable only on top level. Prevents default App::version call, i.e when no version = "version" mentioned.

  • author: author [= "author"]

    Usable only on top level: App::author("author" or env!(CARGO_PKG_AUTHOR)).

    Author/maintainer of the binary, this name appears in help messages. Defaults to the crate author given by cargo, but only when author explicitly mentioned.

  • about: about [= "about"]

    Usable only on top level: App::about("about" or env!(CARGO_PKG_DESCRIPTION)).

    Short description of the binary, appears in help messages. Defaults to the crate description given by cargo, but only when about explicitly mentioned.

  • short: short [= "short-opt-name"]

    Usable only on field-level.

  • long: long [= "long-opt-name"]

    Usable only on field-level.

  • defautl_value: default_value [= "default value"]

    Usable only on field-level.

  • rename_all: [rename_all = "kebab"/"snake"/"screaming-snake"/"camel"/"pascal"/"verbatim"]

    Usable both on top level and field level.

  • parse: parse(type [= path::to::parser::fn])

    Usable only on field-level.

  • skip: skip [= expr]

    Usable only on field-level.

  • flatten: flatten

    Usable only on field-level.

  • subcommand: subcommand

    Usable only on field-level.

  • env: env [= str_literal]

    Usable only on field-level.

  • rename_all_env: [rename_all_env = "kebab"/"snake"/"screaming-snake"/"camel"/"pascal"/"verbatim"]

    Usable both on top level and field level.

  • verbatim_doc_comment: verbatim_doc_comment

    Usable both on top level and field level.