Add ability to hide OptionGroup()

With test

Author: Miguel Perez

Sources/ArgumentParser/Parsable Properties/OptionGroup.swift

@@ -31,6 +31,7 @@
 @propertyWrapper
 public struct OptionGroup<Value: ParsableArguments>: Decodable, ParsedWrapper {
   internal var _parsedValue: Parsed<Value>
+  internal var _hidden: Bool?
 
   internal init(_parsedValue: Parsed<Value>) {
     self._parsedValue = _parsedValue
@@ -84,7 +85,17 @@ extension OptionGroup: CustomStringConvertible {
     case .value(let v):
       return String(describing: v)
     case .definition:
+      if let hidden = _hidden {
+        return "OptionGroup(*definition*) _hidden: \(hidden)"
+      }
       return "OptionGroup(*definition*)"
     }
   }
 }
+
+extension OptionGroup {
+    public init(_hidden: Bool) {
+        self.init()
+        self._hidden = _hidden
+    }
+}

Sources/ArgumentParser/Parsable Types/ParsableArguments.swift

@@ -213,7 +213,7 @@ protocol ArgumentSetProvider {
 }
 
 extension ArgumentSet {
-  init(_ type: ParsableArguments.Type) {
+  init(_ type: ParsableArguments.Type, creatingHelp: Bool = false) {
 
     #if DEBUG
     do {
@@ -228,6 +228,10 @@ extension ArgumentSet {
       .compactMap { child in
         guard var codingKey = child.label else { return nil }
 
+        if creatingHelp {
+          guard !String(describing: child.value).contains("_hidden: true") else { return nil }
+        }
+        
         if let parsed = child.value as? ArgumentSetProvider {
           // Property wrappers have underscore-prefixed names
           codingKey = String(codingKey.first == "_"

Sources/ArgumentParser/Usage/HelpGenerator.swift

@@ -147,13 +147,13 @@ internal struct HelpGenerator {
 
     var commandsToShowHelp = [ParsableCommand.Type]()
     if let commandType = commandStack.last, !commandType.includeSuperCommandInHelp {
-        commandsToShowHelp.append(commandType)
+      commandsToShowHelp.append(commandType)
     } else {
-        commandsToShowHelp = commandStack
+      commandsToShowHelp = commandStack
     }
 
     for commandType in commandsToShowHelp {
-      let args = Array(ArgumentSet(commandType))
+      let args = Array(ArgumentSet(commandType, creatingHelp: true))
 
       var i = 0
       while i < args.count {

Tests/ArgumentParserUnitTests/HelpGenerationTests.swift

@@ -475,4 +475,36 @@ extension HelpGenerationTests {
     
     """)
   }
+    
+  struct optionsToHide: ParsableArguments {
+    @Flag(help: "Verbose")
+    var verbose: Bool = false
+    
+    @Option(help: "Custom Name")
+    var customName: String?
+  }
+    
+  struct HideDriver: ParsableCommand {
+    static let configuration = CommandConfiguration(commandName: "driver", abstract: "Demo hiding option groups")
+    
+    @OptionGroup(_hidden: true)
+    var hideMe: optionsToHide
+    
+    @Option(help: "Time to wait before timeout (in seconds)")
+    var timeout: Int?
+  }
+    
+  func testHidingOptionGroup() throws {
+    AssertHelp(for: HideDriver.self, equals: """
+        OVERVIEW: Demo hiding option groups
+
+        USAGE: driver [--verbose] [--custom-name <custom-name>] [--timeout <timeout>]
+
+        OPTIONS:
+          --timeout <timeout>     Time to wait before timeout (in seconds)
+          -h, --help              Show help information.
+        
+        """
+    )
+  }
 }