Nate Cook
b80fb05f45
This change lets you provide a title for option groups, which is used
when generating the help screen. Titled option groups, when they exist,
are placed between the ARGUMENTS and OPTIONS section of the help.
Multiple option groups with the same title are coalesced into a single
group.
For example, this command declaration:
struct Extras: ParsableArguments {
@Flag(help: "Print extra output while processing.")
var verbose: Bool = false
@Flag(help: "Include details no one asked for.")
var oversharing: Bool = false
}
@main
struct Example: ParsableCommand {
@OptionGroup(title: "Extras")
var extras: Extras
@Argument var name: String?
@Option var title: String?
}
yields this help screen:
USAGE: example [--verbose] [--oversharing] [<name>] [--title <title>]
ARGUMENTS:
<name>
EXTRAS:
--verbose Print extra output while processing.
--oversharing Include details no one asked for.
OPTIONS:
--title <title>
-h, --help Show help information.
5.7 KiB
Customizing Help
Support your users (and yourself) by providing rich help for arguments, options, and flags.
Overview
You can provide help text when declaring any @Argument, @Option, or @Flag by passing a string literal as the help parameter:
struct Example: ParsableCommand {
@Flag(help: "Display extra information while processing.")
var verbose = false
@Option(help: "The number of extra lines to show.")
var extraLines = 0
@Argument(help: "The input file.")
var inputFile: String?
}
Users see these strings in the automatically-generated help screen, which is triggered by the -h or --help flags, by default:
% example --help
USAGE: example [--verbose] [--extra-lines <extra-lines>] <input-file>
ARGUMENTS:
<input-file> The input file.
OPTIONS:
--verbose Display extra information while processing.
--extra-lines <extra-lines>
The number of extra lines to show. (default: 0)
-h, --help Show help information.
Customizing Help for Arguments
For more control over the help text, pass an ArgumentHelp instance instead of a string literal. The ArgumentHelp type can include an abstract (which is what the string literal becomes), a discussion, a value name to use in the usage string, and a visibility level for that argument.
Here's the same command with some extra customization:
struct Example: ParsableCommand {
@Flag(help: "Display extra information while processing.")
var verbose = false
@Option(help: ArgumentHelp(
"The number of extra lines to show.",
valueName: "n"))
var extraLines = 0
@Argument(help: ArgumentHelp(
"The input file.",
discussion: "If no input file is provided, the tool reads from stdin.",
valueName: "file"))
var inputFile: String?
}
...and the help screen:
USAGE: example [--verbose] [--extra-lines <n>] [<file>]
ARGUMENTS:
<file> The input file.
If no input file is provided, the tool reads from stdin.
OPTIONS:
--verbose Display extra information while processing.
--extra-lines <n> The number of extra lines to show. (default: 0)
-h, --help Show help information.
Controlling Argument Visibility
You can specify the visibility of any argument, option, or flag.
struct Example: ParsableCommand {
@Flag(help: ArgumentHelp("Show extra info.", visibility: .hidden))
var verbose: Bool = false
@Flag(help: ArgumentHelp("Use the legacy format.", visibility: .private))
var useLegacyFormat: Bool = false
}
The --verbose flag is only visible in the extended help screen. The --use-legacy-format stays hidden even in the extended help screen, due to its .private visibility.
% example --help
USAGE: example
OPTIONS:
-h, --help Show help information.
% example --help-hidden
USAGE: example [--verbose]
OPTIONS:
--verbose Show extra info.
-h, --help Show help information.
Alternatively, you can group multiple arguments, options, and flags together as part of a ParsableArguments type, and set the visibility when including them as an @OptionGroup property.
struct ExperimentalFlags: ParsableArguments {
@Flag(help: "Use the remote access token. (experimental)")
var experimentalUseRemoteAccessToken: Bool = false
@Flag(help: "Use advanced security. (experimental)")
var experimentalAdvancedSecurity: Bool = false
}
struct Example: ParsableCommand {
@OptionGroup(visibility: .hidden)
var flags: ExperimentalFlags
}
The members of ExperimentalFlags are only shown in the extended help screen:
% example --help
USAGE: example
OPTIONS:
-h, --help Show help information.
% example --help-hidden
USAGE: example [--experimental-use-remote-access-token] [--experimental-advanced-security]
OPTIONS:
--experimental-use-remote-access-token
Use the remote access token. (experimental)
--experimental-advanced-security
Use advanced security. (experimental)
-h, --help Show help information.
Grouping Arguments in the Help Screen
When you provide a title in an @OptionGroup declaration, that type's
properties are grouped together under your title in the help screen.
For example, this command bundles similar arguments together under a
"Build Options" title:
struct BuildOptions: ParsableArguments {
@Option(help: "A setting to pass to the compiler.")
var compilerSetting: [String] = []
@Option(help: "A setting to pass to the linker.")
var linkerSetting: [String] = []
}
struct Example: ParsableCommand {
@Argument(help: "The input file to process.")
var inputFile: String
@Flag(help: "Show extra output.")
var verbose: Bool = false
@Option(help: "The path to a configuration file.")
var configFile: String?
@OptionGroup(title: "Build Options")
var buildOptions: BuildOptions
}
This grouping is reflected in the command's help screen:
% example --help
USAGE: example <input-file> [--verbose] [--config-file <config-file>] [--compiler-setting <compiler-setting> ...] [--linker-setting <linker-setting> ...]
ARGUMENTS:
<input-file> The input file to process.
BUILD OPTIONS:
--compiler-setting <compiler-setting>
A setting to pass to the compiler.
--linker-setting <linker-setting>
A setting to pass to the linker.
OPTIONS:
--verbose Show extra output.
--config-file <config-file>
The path to a configuration file.
-h, --help Show help information.