func unknownOptionMessage()

in Sources/ArgumentParser/Usage/UsageGenerator.swift [272:299]

• 24 lines of code
• 7 McCabe index (conditional complexity)

  func unknownOptionMessage(origin: InputOrigin.Element, name: Name) -> String {
    if case .short = name {
      return "Unknown option '\(name.synopsisString)'"
    }
    
    // An empirically derived magic number
    let SIMILARITY_FLOOR = 4

    let notShort: (Name) -> Bool = { (name: Name) in
      switch name {
      case .short: return false
      case .long: return true
      case .longWithSingleDash: return true
      }
    }
    let suggestion = arguments
      .flatMap({ $0.names })
      .filter({ $0.synopsisString.editDistance(to: name.synopsisString) < SIMILARITY_FLOOR }) // only include close enough suggestion
      .filter(notShort) // exclude short option suggestions
      .min(by: { lhs, rhs in // find the suggestion closest to the argument
        lhs.synopsisString.editDistance(to: name.synopsisString) < rhs.synopsisString.editDistance(to: name.synopsisString)
      })
    
    if let suggestion = suggestion {
      return "Unknown option '\(name.synopsisString)'. Did you mean '\(suggestion.synopsisString)'?"
    }
    return "Unknown option '\(name.synopsisString)'"
  }