[lldb] tab completion for `command script delete'

[MrHate]

Summary

Added the tab completion for command script delete.

[MrHate]

Added arg index check.

[teemperor]

LGTM, thanks!

lldb/include/lldb/Interpreter/CommandInterpreter.h

public:
   void SetPromptOnQuit(bool enable);
 
   bool GetEchoCommands() const;
   void SetEchoCommands(bool enable);
 
   bool GetEchoCommentCommands() const;
   void SetEchoCommentCommands(bool enable);
 
+  const CommandObject::CommandMap &GetUserCommands() const {
+    return m_user_dict;
+  }
+
   /// Specify if the command interpreter should allow that the user can
   /// specify a custom exit code when calling 'quit'.
   void AllowExitCodeOnQuit(bool allow);
 
   /// Sets the exit code for the quit command.
   /// \param[in] exit_code
   ///     The exit code that the driver should return on exit.
   /// \return True if the exit code was successfully set; false if the

lldb/source/Commands/CommandObjectCommands.cpp

CommandObjectCommandsScriptDelete(CommandInterpreter &interpreter)
     arg1.push_back(cmd_arg);
 
     // Push the data for the first argument into the m_arguments vector.
     m_arguments.push_back(arg1);
   }
 
   ~CommandObjectCommandsScriptDelete() override = default;
 
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
+
+    if (!m_interpreter.HasCommands())
+      return;
+    const auto &user_dict = m_interpreter.GetUserCommands();
+
+    for (auto pos = user_dict.begin(); pos != user_dict.end(); ++pos) {
+      request.TryCompleteCurrentArg(pos->first, pos->second->GetHelp());
+    }
+  }
+
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
 
     if (command.GetArgumentCount() != 1) {
       result.AppendError("'command script delete' requires one argument");
       result.SetStatus(eReturnStatusFailed);
       return false;
     }

lldb/test/API/functionalities/completion/TestCompletion.py

def test_command_argument_completion(self):
         self.complete_from_to('watchpoint set variable foo -w', 'watchpoint set variable foo -w ')
         self.complete_from_to("watchpoint set variable foo --", ["--watch", "--size"])
         self.complete_from_to("watchpoint set variable foo --w", "watchpoint set variable foo --watch")
         self.complete_from_to('watchpoint set variable foo -w ', ['read', 'write', 'read_write'])
         self.complete_from_to("watchpoint set variable foo --watch ", ["read", "write", "read_write"])
         self.complete_from_to("watchpoint set variable foo --watch w", "watchpoint set variable foo --watch write")
         self.complete_from_to('watchpoint set variable foo -w read_', 'watchpoint set variable foo -w read_write')
 
+    def test_command_script_delete(self):
+        self.runCmd("command script add -h test_desc -f none -s current usercmd1")
+        self.check_completion_with_desc('command script delete ', [['usercmd1', 'test_desc']])
+
     def test_completion_description_commands(self):
         """Test descriptions of top-level command completions"""
         self.check_completion_with_desc("", [
             ["command", "Commands for managing custom LLDB commands."],
             ["breakpoint", "Commands for operating on breakpoints (see 'help b' for shorthand.)"]
         ])
 
         self.check_completion_with_desc("pl", [