Fix handling of visibility with nested OptionGroups.

Sources/ArgumentParser/Parsable Properties/ArgumentVisibility.swift

@@ -57,4 +57,28 @@ extension ArgumentVisibility {
   internal func isAtLeastAsVisible(as other: Self) -> Bool {
     self.base._comparableLevel >= other.base._comparableLevel
   }
+
+  /// Reduce the visibility to a specified level if it is more restricted than the current value.
+  internal mutating func reduce(to: ArgumentVisibility) {
+    switch to.base {
+    case .default:
+      break  // No effect
+    case .hidden:
+      if case .default = self.base {
+        self.base = .hidden
+      }
+    case .private:
+      self.base = .private
+    }
+  }
+}
+
+extension ArgumentDefinition {
+  internal func reducingHelpVisibility(to visibility: ArgumentVisibility)
+    -> Self
+  {
+    var result = self
+    result.help.visibility.reduce(to: visibility)
+    return result
+  }
 }

Sources/ArgumentParser/Parsable Properties/OptionGroup.swift

@@ -88,6 +88,9 @@ public struct OptionGroup<Value: ParsableArguments>: Decodable, ParsedWrapper {
             $0.help.parentTitle = title
           }
         }
+        args.content = args.content.map { arg in
+          arg.reducingHelpVisibility(to: visibility)
+        }
         return args
       })
     self._visibility = visibility

Sources/ArgumentParser/Parsable Types/ParsableArguments.swift

@@ -301,9 +301,6 @@ extension ArgumentSet {
         guard let codingKey = child.label else { return nil }
 
         if let parsed = child.value as? ArgumentSetProvider {
-          guard parsed._visibility.isAtLeastAsVisible(as: visibility)
-          else { return nil }
-
           let key = InputKey(name: codingKey, parent: parent)
           return parsed.argumentSet(for: key)
         } else {

Tests/ArgumentParserUnitTests/HelpGenerationTests+GroupName.swift

@@ -187,18 +187,23 @@ extension HelpGenerationTests {
         """)
   }
 
+  fileprivate struct NestedGroups: ParsableArguments {
+    @OptionGroup(visibility: .hidden)
+    var flagsAndOptions: FlagsAndOptions
+
+    @OptionGroup(visibility: .private)
+    var argsAndFlags: ArgsAndFlags
+  }
+
   fileprivate struct HiddenGroups: ParsableCommand {
     @OptionGroup(title: "Flags Group", visibility: .hidden)
     var flags: Flags
 
     @OptionGroup(title: "Options Group", visibility: .hidden)
     var options: Options
 
-    @OptionGroup(visibility: .hidden)
-    var flagsAndOptions: FlagsAndOptions
-
-    @OptionGroup(visibility: .private)
-    var argsAndFlags: ArgsAndFlags
+    @OptionGroup()
+    var nested: NestedGroups
   }
 
   func testHiddenGroups() {