Hide hidden subcommands from completions

Sources/ArgumentParser/Completions/BashCompletionsGenerator.swift

@@ -35,6 +35,7 @@ struct BashCompletionsGenerator {
 
     // Include 'help' in the list of subcommands for the root command.
     var subcommands = type.configuration.subcommands
+      .filter { $0.configuration.shouldDisplay }
     if !subcommands.isEmpty && isRootCommand {
       subcommands.append(HelpCommand.self)
     }

Sources/ArgumentParser/Completions/FishCompletionsGenerator.swift

@@ -30,6 +30,7 @@ struct FishCompletionsGenerator {
     let isRootCommand = commands.count == 1
     let programName = commandChain[0]
     var subcommands = type.configuration.subcommands
+      .filter { $0.configuration.shouldDisplay }
 
     if !subcommands.isEmpty {
       if isRootCommand {

Sources/ArgumentParser/Completions/ZshCompletionsGenerator.swift

@@ -37,6 +37,7 @@ struct ZshCompletionsGenerator {
 
     var args = generateCompletionArguments(commands)    
     var subcommands = type.configuration.subcommands
+      .filter { $0.configuration.shouldDisplay }
     var subcommandHandler = ""
     if !subcommands.isEmpty {
       args.append("'(-): :->command'")

Tests/ArgumentParserUnitTests/CompletionScriptTests.swift

@@ -268,3 +268,114 @@ complete -c base -n '_swift_base_using_command base' -f -r -l path3
 complete -c base -n '_swift_base_using_command base --path3' -f -k -a 'a b c'
 complete -c base -n '_swift_base_using_command base' -f -s h -l help -d 'Show help information.'
 """
+
+// MARK: - Test Hidden Subcommand
+struct Parent: ParsableCommand {
+    static var configuration = CommandConfiguration(subcommands: [HiddenChild.self])
+}
+
+struct HiddenChild: ParsableCommand {
+    static var configuration = CommandConfiguration(shouldDisplay: false)
+}
+
+extension CompletionScriptTests {
+  func testHiddenSubcommand_Zsh() throws {
+    let script1 = try CompletionsGenerator(command: Parent.self, shell: .zsh)
+          .generateCompletionScript()
+    XCTAssertEqual(zshHiddenCompletion, script1)
+
+    let script2 = try CompletionsGenerator(command: Parent.self, shellName: "zsh")
+          .generateCompletionScript()
+    XCTAssertEqual(zshHiddenCompletion, script2)
+
+    let script3 = Parent.completionScript(for: .zsh)
+    XCTAssertEqual(zshHiddenCompletion, script3)
+  }
+
+  func testHiddenSubcommand_Bash() throws {
+    let script1 = try CompletionsGenerator(command: Parent.self, shell: .bash)
+          .generateCompletionScript()
+    XCTAssertEqual(bashHiddenCompletion, script1)
+
+    let script2 = try CompletionsGenerator(command: Parent.self, shellName: "bash")
+          .generateCompletionScript()
+    XCTAssertEqual(bashHiddenCompletion, script2)
+
+    let script3 = Parent.completionScript(for: .bash)
+    XCTAssertEqual(bashHiddenCompletion, script3)
+  }
+
+  func testHiddenSubcommand_Fish() throws {
+    let script1 = try CompletionsGenerator(command: Parent.self, shell: .fish)
+          .generateCompletionScript()
+    XCTAssertEqual(fishHiddenCompletion, script1)
+
+    let script2 = try CompletionsGenerator(command: Parent.self, shellName: "fish")
+          .generateCompletionScript()
+    XCTAssertEqual(fishHiddenCompletion, script2)
+
+    let script3 = Parent.completionScript(for: .fish)
+    XCTAssertEqual(fishHiddenCompletion, script3)
+  }
+}
+
+let zshHiddenCompletion = """
+#compdef parent
+local context state state_descr line
+_parent_commandname=$words[1]
+typeset -A opt_args
+
+_parent() {
+    integer ret=1
+    local -a args
+    args+=(
+        '(-h --help)'{-h,--help}'[Show help information.]'
+    )
+    _arguments -w -s -S $args[@] && ret=0
+
+    return ret
+}
+
+
+_custom_completion() {
+    local completions=("${(@f)$($*)}")
+    _describe '' completions
+}
+
+_parent
+"""
+
+let bashHiddenCompletion = """
+#!/bin/bash
+
+_parent() {
+    cur="${COMP_WORDS[COMP_CWORD]}"
+    prev="${COMP_WORDS[COMP_CWORD-1]}"
+    COMPREPLY=()
+    opts="-h --help"
+    if [[ $COMP_CWORD == "1" ]]; then
+        COMPREPLY=( $(compgen -W "$opts" -- "$cur") )
+        return
+    fi
+    COMPREPLY=( $(compgen -W "$opts" -- "$cur") )
+}
+
+
+complete -F _parent parent
+"""
+
+let fishHiddenCompletion = """
+function _swift_parent_using_command
+    set -l cmd (commandline -opc)
+    if [ (count $cmd) -eq (count $argv) ]
+        for i in (seq (count $argv))
+            if [ $cmd[$i] != $argv[$i] ]
+                return 1
+            end
+        end
+        return 0
+    end
+    return 1
+end
+complete -c parent -n '_swift_parent_using_command parent' -f -s h -l help -d 'Show help information.'
+"""