/
Argument.swift
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/
Argument.swift
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//===----------------------------------------------------------*- swift -*-===//
//
// This source file is part of the Swift Argument Parser open source project
//
// Copyright (c) 2020 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
/// A property wrapper that represents a positional command-line argument.
///
/// Use the `@Argument` wrapper to define a property of your custom command as
/// a positional argument. A *positional argument* for a command-line tool is
/// specified without a label and must appear in declaration order. `@Argument`
/// properties with `Optional` type or a default value are optional for the user
/// of your command-line tool.
///
/// For example, the following program has two positional arguments. The `name`
/// argument is required, while `greeting` is optional because it has a default
/// value.
///
/// @main
/// struct Greet: ParsableCommand {
/// @Argument var name: String
/// @Argument var greeting: String = "Hello"
///
/// mutating func run() {
/// print("\(greeting) \(name)!")
/// }
/// }
///
/// You can call this program with just a name or with a name and a
/// greeting. When you supply both arguments, the first argument is always
/// treated as the name, due to the order of the property declarations.
///
/// $ greet Nadia
/// Hello Nadia!
/// $ greet Tamara Hi
/// Hi Tamara!
@propertyWrapper
public struct Argument<Value>:
Decodable, ParsedWrapper
{
internal var _parsedValue: Parsed<Value>
internal init(_parsedValue: Parsed<Value>) {
self._parsedValue = _parsedValue
}
public init(from decoder: Decoder) throws {
try self.init(_decoder: decoder)
}
/// This initializer works around a quirk of property wrappers, where the
/// compiler will not see no-argument initializers in extensions. Explicitly
/// marking this initializer unavailable means that when `Value` conforms to
/// `ExpressibleByArgument`, that overload will be selected instead.
///
/// ```swift
/// @Argument() var foo: String // Syntax without this initializer
/// @Argument var foo: String // Syntax with this initializer
/// ```
@available(*, unavailable, message: "A default value must be provided unless the value type conforms to ExpressibleByArgument.")
public init() {
fatalError("unavailable")
}
/// The value presented by this property wrapper.
public var wrappedValue: Value {
get {
switch _parsedValue {
case .value(let v):
return v
case .definition:
fatalError(directlyInitializedError)
}
}
set {
_parsedValue = .value(newValue)
}
}
}
extension Argument: CustomStringConvertible {
public var description: String {
switch _parsedValue {
case .value(let v):
return String(describing: v)
case .definition:
return "Argument(*definition*)"
}
}
}
extension Argument: DecodableParsedWrapper where Value: Decodable { }
/// The strategy to use when parsing multiple values from positional arguments
/// into an array.
public struct ArgumentArrayParsingStrategy: Hashable {
internal var base: ArgumentDefinition.ParsingStrategy
/// Parse only unprefixed values from the command-line input, ignoring
/// any inputs that have a dash prefix. This is the default strategy.
///
/// For example, for a parsable type defined as following:
///
/// struct Options: ParsableArguments {
/// @Flag var verbose: Bool
/// @Argument(parsing: .remaining) var words: [String]
/// }
///
/// Parsing the input `--verbose one two` or `one two --verbose` would result
/// in `Options(verbose: true, words: ["one", "two"])`. Parsing the input
/// `one two --other` would result in an unknown option error for `--other`.
///
/// This is the default strategy for parsing argument arrays.
public static var remaining: ArgumentArrayParsingStrategy {
self.init(base: .default)
}
/// Parse all remaining inputs after parsing any known options or flags,
/// including dash-prefixed inputs and the `--` terminator.
///
/// When you use the `unconditionalRemaining` parsing strategy, the parser
/// stops parsing flags and options as soon as it encounters a positional
/// argument or an unrecognized flag. For example, for a parsable type
/// defined as following:
///
/// struct Options: ParsableArguments {
/// @Flag
/// var verbose: Bool = false
///
/// @Argument(parsing: .unconditionalRemaining)
/// var words: [String] = []
/// }
///
/// Parsing the input `--verbose one two --verbose` includes the second
/// `--verbose` flag in `words`, resulting in
/// `Options(verbose: true, words: ["one", "two", "--verbose"])`.
///
/// - Note: This parsing strategy can be surprising for users, particularly
/// when combined with options and flags. Prefer `remaining` whenever
/// possible, since users can always terminate options and flags with
/// the `--` terminator. With the `remaining` parsing strategy, the input
/// `--verbose -- one two --verbose` would have the same result as the above
/// example: `Options(verbose: true, words: ["one", "two", "--verbose"])`.
public static var unconditionalRemaining: ArgumentArrayParsingStrategy {
self.init(base: .allRemainingInput)
}
}
// MARK: - @Argument T: ExpressibleByArgument Initializers
extension Argument {
/// Creates a property with a default value provided by standard Swift default
/// value syntax.
///
/// This method is called to initialize an `Argument` with a default value
/// such as:
/// ```swift
/// @Argument var foo: String = "bar"
/// ```
///
/// - Parameters:
/// - wrappedValue: A default value to use for this property, provided
/// implicitly by the compiler during property wrapper initialization.
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
public init(
wrappedValue: Value,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where Value: ExpressibleByArgument {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Bare<Value>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
initial: wrappedValue,
completion: completion)
return ArgumentSet(arg)
})
}
/// Creates a property with no default value.
///
/// This method is called to initialize an `Argument` without a default value
/// such as:
/// ```swift
/// @Argument var foo: String
/// ```
///
/// - Parameters:
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
public init(
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where Value: ExpressibleByArgument {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Bare<Value>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
}
// MARK: - @Argument T Initializers
extension Argument {
/// Creates a property with a default value provided by standard Swift default
/// value syntax, parsing with the given closure.
///
/// This method is called to initialize an `Argument` with a default value
/// such as:
/// ```swift
/// @Argument(transform: baz)
/// var foo: String = "bar"
/// ```
///
/// - Parameters:
/// - wrappedValue: A default value to use for this property, provided
/// implicitly by the compiler during property wrapper initialization.
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
/// - transform: A closure that converts a string into this property's type
/// or throws an error.
public init(
wrappedValue: Value,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> Value
) {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Bare<Value>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
transform: transform,
initial: wrappedValue,
completion: completion)
return ArgumentSet(arg)
})
}
/// Creates a property with no default value, parsing with the given closure.
///
/// This method is called to initialize an `Argument` with no default value such as:
/// ```swift
/// @Argument(transform: baz)
/// var foo: String
/// ```
///
/// - Parameters:
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
/// - transform: A closure that converts a string into this property's
/// element type or throws an error.
public init(
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> Value
) {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Bare<Value>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
transform: transform,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
}
// MARK: - @Argument Optional<T: ExpressibleByArgument> Initializers
extension Argument {
/// This initializer allows a user to provide a `nil` default value for an
/// optional `@Argument`-marked property without allowing a non-`nil` default
/// value.
///
/// - Parameters:
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
public init<T>(
wrappedValue _value: _OptionalNilComparisonType,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where T: ExpressibleByArgument, Value == Optional<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Optional<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
@available(*, deprecated, message: """
Optional @Arguments with default values should be declared as non-Optional.
""")
public init<T>(
wrappedValue: Optional<T>,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where T: ExpressibleByArgument, Value == Optional<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Optional<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
initial: wrappedValue,
completion: completion)
return ArgumentSet(arg)
})
}
/// Creates an optional property that reads its value from an argument.
///
/// The argument is optional for the caller of the command and defaults to
/// `nil`.
///
/// - Parameters:
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
public init<T>(
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where T: ExpressibleByArgument, Value == Optional<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Optional<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
}
// MARK: - @Argument Optional<T> Initializers
extension Argument {
/// This initializer allows a user to provide a `nil` default value for an
/// optional `@Argument`-marked property without allowing a non-`nil` default
/// value.
///
/// - Parameters:
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
/// - transform: A closure that converts a string into this property's
/// element type or throws an error.
public init<T>(
wrappedValue _value: _OptionalNilComparisonType,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> T
) where Value == Optional<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Optional<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
transform: transform,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
@available(*, deprecated, message: """
Optional @Arguments with default values should be declared as non-Optional.
""")
public init<T>(
wrappedValue: Optional<T>,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> T
) where Value == Optional<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Optional<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
transform: transform,
initial: wrappedValue,
completion: completion)
return ArgumentSet(arg)
})
}
/// Creates an optional property that reads its value from an argument.
///
/// The argument is optional for the caller of the command and defaults to
/// `nil`.
///
/// - Parameters:
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
/// - transform: A closure that converts a string into this property's
/// element type or throws an error.
public init<T>(
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> T
) where Value == Optional<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Optional<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: .default,
transform: transform,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
}
// MARK: - @Argument Array<T: ExpressibleByArgument> Initializers
extension Argument {
/// Creates a property that reads an array from zero or more arguments.
///
/// - Parameters:
/// - initial: A default value to use for this property.
/// - parsingStrategy: The behavior to use when parsing multiple values from
/// the command-line arguments.
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
public init<T>(
wrappedValue: Array<T>,
parsing parsingStrategy: ArgumentArrayParsingStrategy = .remaining,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where T: ExpressibleByArgument, Value == Array<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Array<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: parsingStrategy.base,
initial: wrappedValue,
completion: completion)
return ArgumentSet(arg)
})
}
/// Creates a property with no default value that reads an array from zero or
/// more arguments.
///
/// This method is called to initialize an array `Argument` with no default
/// value such as:
/// ```swift
/// @Argument()
/// var foo: [String]
/// ```
///
/// - Parameters:
/// - parsingStrategy: The behavior to use when parsing multiple values from
/// the command-line arguments.
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
public init<T>(
parsing parsingStrategy: ArgumentArrayParsingStrategy = .remaining,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil
) where T: ExpressibleByArgument, Value == Array<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Array<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: parsingStrategy.base,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
}
// MARK: - @Argument Array<T> Initializers
extension Argument {
/// Creates a property that reads an array from zero or more arguments,
/// parsing each element with the given closure.
///
/// - Parameters:
/// - wrappedValue: A default value to use for this property.
/// - parsingStrategy: The behavior to use when parsing multiple values from
/// the command-line arguments.
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
/// - transform: A closure that converts a string into this property's
/// element type or throws an error.
public init<T>(
wrappedValue: Array<T>,
parsing parsingStrategy: ArgumentArrayParsingStrategy = .remaining,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> T
) where Value == Array<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Array<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: parsingStrategy.base,
transform: transform,
initial: wrappedValue,
completion: completion)
return ArgumentSet(arg)
})
}
/// Creates a property with no default value that reads an array from zero or
/// more arguments, parsing each element with the given closure.
///
/// This method is called to initialize an array `Argument` with no default
/// value such as:
/// ```swift
/// @Argument(transform: baz)
/// var foo: [String]
/// ```
///
/// - Parameters:
/// - parsingStrategy: The behavior to use when parsing multiple values from
/// the command-line arguments.
/// - help: Information about how to use this argument.
/// - completion: Kind of completion provided to the user for this option.
/// - transform: A closure that converts a string into this property's
/// element type or throws an error.
public init<T>(
parsing parsingStrategy: ArgumentArrayParsingStrategy = .remaining,
help: ArgumentHelp? = nil,
completion: CompletionKind? = nil,
transform: @escaping (String) throws -> T
) where Value == Array<T> {
self.init(_parsedValue: .init { key in
let arg = ArgumentDefinition(
container: Array<T>.self,
key: key,
kind: .positional,
help: help,
parsingStrategy: parsingStrategy.base,
transform: transform,
initial: nil,
completion: completion)
return ArgumentSet(arg)
})
}
}