An array with no default value should be interpreted as an argument with at least one required element

[dabrahams]

struct Example: ParsableCommand {
    @Argument var files: [String] = []
    @Option var count: Int?
    @Option var index = 0
    @Flag var verbose = false
    @Flag var stripWhitespace = false
}

In this example from the docs, if I wanted to require that at least one file was supplied, I think I should be able to write:

struct Example: ParsableCommand {
    @Argument var files: [String]
    @Option var count: Int?
    @Option var index = 0
    @Flag var verbose = false
    @Flag var stripWhitespace = false
}

[rauhul]

(Disclaimer: I'm not in the office this week nor have access to a laptop)

I believe your example should work as you described and if it doesn't this is a bug.

Could you attach the swift/argument-parser versions as well as the actual vs expected CLI output?

I will try to take a look asap when I return from break 😃

[dabrahams]

Not in a position to check right now, but it may be that this just fails when using a transform on the elements

[rauhul]

FWIW the two snippets above prepended with the following snippet work as expected:

import ArgumentParser

@main
extension Example { 
    func run() throws { print(self) }
}

Swift: 5.9 ArgumentParser: 1.2.2 (fee6933f37fde9a5e12a1e4aeaa93fe60116ff2a)

[natecook1000]

Hi @dabrahams! I've confirmed that this works as expected, with both transformed and ExpressibleByArgument element types. If you're still seeing this, feel free to re-open with a reproducing example.

Here's an example with a transform closure:

@main
struct Repeat: ParsableCommand {
  @Option(help: "The number of times to repeat 'phrases'. (default: forever)")
  var count: Int?

  @Argument(help: "The phrases to repeat.", transform: { $0.uppercased() })
  var phrases: [String]

  mutating func run() throws {
    for _ in 1...(count ?? .max) {
      print(phrases.joined(separator: "\n"))
    }
  }
}

Output:

$ swift run repeat
Error: Missing expected argument '<phrases> ...'

USAGE: repeat [--count <count>] <phrases> ...

ARGUMENTS:
  <phrases>               The phrases to repeat.

OPTIONS:
  --count <count>         The number of times to repeat 'phrases'. (default: forever)
  -h, --help              Show help information.

$ swift run repeat one two three --count 2
ONE
TWO
THREE
ONE
TWO
THREE

[dabrahams]

Thanks for checking it out. I'm sorry if this report wasted your time; I filed it from a memory of something that hadn't worked out, without a reproducer.