Have CommandObjectParsed check for "commands that take no arguments".

This is currently being done in an ad hoc way, and so for some
commands it isn't being checked.  We have the info to make this check,
since commands are supposed to add their arguments to the m_arguments
field of the CommandObject.  This change uses that info to check whether
the command received arguments in error.

A handful of commands weren't defining their argument types, I also had
to fix them.  And a bunch of commands were checking for arguments by
hand, so I removed those checks in favor of the CommandObject one.  That
also meant I had to change some tests that were checking for the ad hoc
error outputs.

Differential Revision: https://reviews.llvm.org/D128453

13 files changed, 197 insertions, 221 deletions

diff --git a/lldb/source/Commands/CommandObjectCommands.cpp b/lldb/source/Commands/CommandObjectCommands.cpp
index 2334759..39c7207 100644
--- a/lldb/source/Commands/CommandObjectCommands.cpp
+++ b/lldb/source/Commands/CommandObjectCommands.cpp
@@ -824,6 +824,8 @@ a number follows 'f':"
         R"(
 
     (lldb) command regex f s/^$/finish/ 's/([0-9]+)/frame select %1/')");
+    CommandArgumentData thread_arg{eArgTypeSEDStylePair, eArgRepeatOptional};
+    m_arguments.push_back({thread_arg});
   }
 
   ~CommandObjectCommandsAddRegex() override = default;
@@ -1664,11 +1666,6 @@ public:
   ~CommandObjectCommandsScriptList() override = default;
 
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (command.GetArgumentCount() != 0) {
-      result.AppendError("'command script list' doesn't take any arguments");
-      return false;
-    }
-
     m_interpreter.GetHelp(result, CommandInterpreter::eCommandTypesUserDef);
 
     result.SetStatus(eReturnStatusSuccessFinishResult);
@@ -1689,11 +1686,6 @@ public:
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (command.GetArgumentCount() != 0) {
-      result.AppendError("'command script clear' doesn't take any arguments");
-      return false;
-    }
-
     m_interpreter.RemoveAllUser();
 
     result.SetStatus(eReturnStatusSuccessFinishResult);
diff --git a/lldb/source/Commands/CommandObjectFrame.cpp b/lldb/source/Commands/CommandObjectFrame.cpp
index 93c41ee..9f2c79d 100644
--- a/lldb/source/Commands/CommandObjectFrame.cpp
+++ b/lldb/source/Commands/CommandObjectFrame.cpp
@@ -924,7 +924,11 @@ class CommandObjectFrameRecognizerDelete : public CommandObjectParsed {
 public:
   CommandObjectFrameRecognizerDelete(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "frame recognizer delete",
-                            "Delete an existing frame recognizer.", nullptr) {}
+                            "Delete an existing frame recognizer by id.",
+                            nullptr) {
+    CommandArgumentData thread_arg{eArgTypeRecognizerID, eArgRepeatPlain};
+    m_arguments.push_back({thread_arg});
+  }
 
   ~CommandObjectFrameRecognizerDelete() override = default;
 
diff --git a/lldb/source/Commands/CommandObjectGUI.cpp b/lldb/source/Commands/CommandObjectGUI.cpp
index 86c47a2..a63d171 100644
--- a/lldb/source/Commands/CommandObjectGUI.cpp
+++ b/lldb/source/Commands/CommandObjectGUI.cpp
@@ -26,22 +26,18 @@ CommandObjectGUI::~CommandObjectGUI() = default;
 
 bool CommandObjectGUI::DoExecute(Args &args, CommandReturnObject &result) {
 #if LLDB_ENABLE_CURSES
-  if (args.GetArgumentCount() == 0) {
-    Debugger &debugger = GetDebugger();
-
-    File &input = debugger.GetInputFile();
-    File &output = debugger.GetOutputFile();
-    if (input.GetStream() && output.GetStream() && input.GetIsRealTerminal() &&
-        input.GetIsInteractive()) {
-      IOHandlerSP io_handler_sp(new IOHandlerCursesGUI(debugger));
-      if (io_handler_sp)
-        debugger.RunIOHandlerAsync(io_handler_sp);
-      result.SetStatus(eReturnStatusSuccessFinishResult);
-    } else {
-      result.AppendError("the gui command requires an interactive terminal.");
-    }
+  Debugger &debugger = GetDebugger();
+
+  File &input = debugger.GetInputFile();
+  File &output = debugger.GetOutputFile();
+  if (input.GetStream() && output.GetStream() && input.GetIsRealTerminal() &&
+      input.GetIsInteractive()) {
+    IOHandlerSP io_handler_sp(new IOHandlerCursesGUI(debugger));
+    if (io_handler_sp)
+      debugger.RunIOHandlerAsync(io_handler_sp);
+    result.SetStatus(eReturnStatusSuccessFinishResult);
   } else {
-    result.AppendError("the gui command takes no arguments.");
+    result.AppendError("the gui command requires an interactive terminal.");
   }
   return true;
 #else
diff --git a/lldb/source/Commands/CommandObjectPlatform.cpp b/lldb/source/Commands/CommandObjectPlatform.cpp
index 774ef6c..42b19db 100644
--- a/lldb/source/Commands/CommandObjectPlatform.cpp
+++ b/lldb/source/Commands/CommandObjectPlatform.cpp
@@ -150,6 +150,8 @@ public:
   {
     m_option_group.Append(&m_platform_options, LLDB_OPT_SET_ALL, 1);
     m_option_group.Finalize();
+    CommandArgumentData platform_arg{eArgTypePlatform, eArgRepeatPlain};
+    m_arguments.push_back({platform_arg});
   }
 
   ~CommandObjectPlatformSelect() override = default;
@@ -271,7 +273,10 @@ public:
       : CommandObjectParsed(
             interpreter, "platform connect",
             "Select the current platform by providing a connection URL.",
-            "platform connect <connect-url>", 0) {}
+            "platform connect <connect-url>", 0) {
+    CommandArgumentData platform_arg{eArgTypeConnectURL, eArgRepeatPlain};
+    m_arguments.push_back({platform_arg});
+  }
 
   ~CommandObjectPlatformConnect() override = default;
 
@@ -415,7 +420,10 @@ public:
   CommandObjectPlatformMkDir(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "platform mkdir",
                             "Make a new directory on the remote end.", nullptr,
-                            0) {}
+                            0) {
+    CommandArgumentData thread_arg{eArgTypePath, eArgRepeatPlain};
+    m_arguments.push_back({thread_arg});
+  }
 
   ~CommandObjectPlatformMkDir() override = default;
 
@@ -461,7 +469,10 @@ class CommandObjectPlatformFOpen : public CommandObjectParsed {
 public:
   CommandObjectPlatformFOpen(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "platform file open",
-                            "Open a file on the remote end.", nullptr, 0) {}
+                            "Open a file on the remote end.", nullptr, 0) {
+    CommandArgumentData path_arg{eArgTypePath, eArgRepeatPlain};
+    m_arguments.push_back({path_arg});
+  }
 
   ~CommandObjectPlatformFOpen() override = default;
 
@@ -521,7 +532,10 @@ class CommandObjectPlatformFClose : public CommandObjectParsed {
 public:
   CommandObjectPlatformFClose(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "platform file close",
-                            "Close a file on the remote end.", nullptr, 0) {}
+                            "Close a file on the remote end.", nullptr, 0) {
+    CommandArgumentData path_arg{eArgTypeUnsignedInteger, eArgRepeatPlain};
+    m_arguments.push_back({path_arg});
+  }
 
   ~CommandObjectPlatformFClose() override = default;
 
@@ -562,7 +576,10 @@ public:
   CommandObjectPlatformFRead(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "platform file read",
                             "Read data from a file on the remote end.", nullptr,
-                            0) {}
+                            0) {
+    CommandArgumentData path_arg{eArgTypeUnsignedInteger, eArgRepeatPlain};
+    m_arguments.push_back({path_arg});
+  }
 
   ~CommandObjectPlatformFRead() override = default;
 
@@ -655,7 +672,10 @@ public:
   CommandObjectPlatformFWrite(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "platform file write",
                             "Write data to a file on the remote end.", nullptr,
-                            0) {}
+                            0) {
+    CommandArgumentData path_arg{eArgTypeUnsignedInteger, eArgRepeatPlain};
+    m_arguments.push_back({path_arg});
+  }
 
   ~CommandObjectPlatformFWrite() override = default;
 
@@ -1070,6 +1090,10 @@ public:
     Relative source file paths are resolved against lldb's local working directory.
 
     Omitting the destination places the file in the platform working directory.)");
+    CommandArgumentData source_arg{eArgTypePath, eArgRepeatPlain};
+    CommandArgumentData path_arg{eArgTypePath, eArgRepeatOptional};
+    m_arguments.push_back({source_arg});
+    m_arguments.push_back({path_arg});
   }
 
   ~CommandObjectPlatformPutFile() override = default;
@@ -1121,6 +1145,8 @@ public:
                             eCommandRequiresTarget | eCommandTryTargetAPILock) {
     m_all_options.Append(&m_options);
     m_all_options.Finalize();
+    CommandArgumentData run_arg_arg{eArgTypeRunArgs, eArgRepeatStar};
+    m_arguments.push_back({run_arg_arg});
   }
 
   ~CommandObjectPlatformProcessLaunch() override = default;
@@ -1229,83 +1255,78 @@ protected:
 
     if (platform_sp) {
       Status error;
-      if (args.GetArgumentCount() == 0) {
-        if (platform_sp) {
-          Stream &ostrm = result.GetOutputStream();
-
-          lldb::pid_t pid =
-              m_options.match_info.GetProcessInfo().GetProcessID();
-          if (pid != LLDB_INVALID_PROCESS_ID) {
-            ProcessInstanceInfo proc_info;
-            if (platform_sp->GetProcessInfo(pid, proc_info)) {
-              ProcessInstanceInfo::DumpTableHeader(ostrm, m_options.show_args,
-                                                   m_options.verbose);
-              proc_info.DumpAsTableRow(ostrm, platform_sp->GetUserIDResolver(),
-                                       m_options.show_args, m_options.verbose);
-              result.SetStatus(eReturnStatusSuccessFinishResult);
-            } else {
-              result.AppendErrorWithFormat(
-                  "no process found with pid = %" PRIu64 "\n", pid);
-            }
+      if (platform_sp) {
+        Stream &ostrm = result.GetOutputStream();
+
+        lldb::pid_t pid = m_options.match_info.GetProcessInfo().GetProcessID();
+        if (pid != LLDB_INVALID_PROCESS_ID) {
+          ProcessInstanceInfo proc_info;
+          if (platform_sp->GetProcessInfo(pid, proc_info)) {
+            ProcessInstanceInfo::DumpTableHeader(ostrm, m_options.show_args,
+                                                 m_options.verbose);
+            proc_info.DumpAsTableRow(ostrm, platform_sp->GetUserIDResolver(),
+                                     m_options.show_args, m_options.verbose);
+            result.SetStatus(eReturnStatusSuccessFinishResult);
           } else {
-            ProcessInstanceInfoList proc_infos;
-            const uint32_t matches =
-                platform_sp->FindProcesses(m_options.match_info, proc_infos);
-            const char *match_desc = nullptr;
-            const char *match_name =
-                m_options.match_info.GetProcessInfo().GetName();
-            if (match_name && match_name[0]) {
-              switch (m_options.match_info.GetNameMatchType()) {
-              case NameMatch::Ignore:
-                break;
-              case NameMatch::Equals:
-                match_desc = "matched";
-                break;
-              case NameMatch::Contains:
-                match_desc = "contained";
-                break;
-              case NameMatch::StartsWith:
-                match_desc = "started with";
-                break;
-              case NameMatch::EndsWith:
-                match_desc = "ended with";
-                break;
-              case NameMatch::RegularExpression:
-                match_desc = "matched the regular expression";
-                break;
-              }
+            result.AppendErrorWithFormat(
+                "no process found with pid = %" PRIu64 "\n", pid);
+          }
+        } else {
+          ProcessInstanceInfoList proc_infos;
+          const uint32_t matches =
+              platform_sp->FindProcesses(m_options.match_info, proc_infos);
+          const char *match_desc = nullptr;
+          const char *match_name =
+              m_options.match_info.GetProcessInfo().GetName();
+          if (match_name && match_name[0]) {
+            switch (m_options.match_info.GetNameMatchType()) {
+            case NameMatch::Ignore:
+              break;
+            case NameMatch::Equals:
+              match_desc = "matched";
+              break;
+            case NameMatch::Contains:
+              match_desc = "contained";
+              break;
+            case NameMatch::StartsWith:
+              match_desc = "started with";
+              break;
+            case NameMatch::EndsWith:
+              match_desc = "ended with";
+              break;
+            case NameMatch::RegularExpression:
+              match_desc = "matched the regular expression";
+              break;
             }
+          }
 
-            if (matches == 0) {
-              if (match_desc)
-                result.AppendErrorWithFormatv(
-                    "no processes were found that {0} \"{1}\" on the \"{2}\" "
-                    "platform\n",
-                    match_desc, match_name, platform_sp->GetName());
-              else
-                result.AppendErrorWithFormatv(
-                    "no processes were found on the \"{0}\" platform\n",
-                    platform_sp->GetName());
-            } else {
-              result.AppendMessageWithFormatv(
-                  "{0} matching process{1} found on \"{2}\"", matches,
-                  matches > 1 ? "es were" : " was", platform_sp->GetName());
-              if (match_desc)
-                result.AppendMessageWithFormat(" whose name %s \"%s\"",
-                                               match_desc, match_name);
-              result.AppendMessageWithFormat("\n");
-              ProcessInstanceInfo::DumpTableHeader(ostrm, m_options.show_args,
-                                                   m_options.verbose);
-              for (uint32_t i = 0; i < matches; ++i) {
-                proc_infos[i].DumpAsTableRow(
-                    ostrm, platform_sp->GetUserIDResolver(),
-                    m_options.show_args, m_options.verbose);
-              }
+          if (matches == 0) {
+            if (match_desc)
+              result.AppendErrorWithFormatv(
+                  "no processes were found that {0} \"{1}\" on the \"{2}\" "
+                  "platform\n",
+                  match_desc, match_name, platform_sp->GetName());
+            else
+              result.AppendErrorWithFormatv(
+                  "no processes were found on the \"{0}\" platform\n",
+                  platform_sp->GetName());
+          } else {
+            result.AppendMessageWithFormatv(
+                "{0} matching process{1} found on \"{2}\"", matches,
+                matches > 1 ? "es were" : " was", platform_sp->GetName());
+            if (match_desc)
+              result.AppendMessageWithFormat(" whose name %s \"%s\"",
+                                             match_desc, match_name);
+            result.AppendMessageWithFormat("\n");
+            ProcessInstanceInfo::DumpTableHeader(ostrm, m_options.show_args,
+                                                 m_options.verbose);
+            for (uint32_t i = 0; i < matches; ++i) {
+              proc_infos[i].DumpAsTableRow(
+                  ostrm, platform_sp->GetUserIDResolver(), m_options.show_args,
+                  m_options.verbose);
             }
           }
         }
-      } else {
-        result.AppendError("invalid args: process list takes only options\n");
       }
     } else {
       result.AppendError("no platform is selected\n");
@@ -1737,7 +1758,10 @@ public:
   CommandObjectPlatformShell(CommandInterpreter &interpreter)
       : CommandObjectRaw(interpreter, "platform shell",
                          "Run a shell command on the current platform.",
-                         "platform shell <shell-command>", 0) {}
+                         "platform shell <shell-command>", 0) {
+    CommandArgumentData thread_arg{eArgTypeNone, eArgRepeatStar};
+    m_arguments.push_back({thread_arg});
+  }
 
   ~CommandObjectPlatformShell() override = default;
 
@@ -1824,7 +1848,12 @@ public:
       : CommandObjectParsed(
             interpreter, "platform target-install",
             "Install a target (bundle or executable file) to the remote end.",
-            "platform target-install <local-thing> <remote-sandbox>", 0) {}
+            "platform target-install <local-thing> <remote-sandbox>", 0) {
+    CommandArgumentData local_arg{eArgTypePath, eArgRepeatPlain};
+    CommandArgumentData remote_arg{eArgTypePath, eArgRepeatPlain};
+    m_arguments.push_back({local_arg});
+    m_arguments.push_back({remote_arg});
+  }
 
   ~CommandObjectPlatformInstall() override = default;
 
diff --git a/lldb/source/Commands/CommandObjectProcess.cpp b/lldb/source/Commands/CommandObjectProcess.cpp
index 2f5f649..c76ae990 100644
--- a/lldb/source/Commands/CommandObjectProcess.cpp
+++ b/lldb/source/Commands/CommandObjectProcess.cpp
@@ -414,12 +414,6 @@ protected:
     ModuleSP old_exec_module_sp = target->GetExecutableModule();
     ArchSpec old_arch_spec = target->GetArchitecture();
 
-    if (command.GetArgumentCount()) {
-      result.AppendErrorWithFormat("Invalid arguments for '%s'.\nUsage: %s\n",
-                                   m_cmd_name.c_str(), m_cmd_syntax.c_str());
-      return false;
-    }
-
     StreamString stream;
     ProcessSP process_sp;
     const auto error = target->Attach(m_options.attach_info, &stream);
@@ -562,13 +556,6 @@ protected:
     bool synchronous_execution = m_interpreter.GetSynchronous();
     StateType state = process->GetState();
     if (state == eStateStopped) {
-      if (command.GetArgumentCount() != 0) {
-        result.AppendErrorWithFormat(
-            "The '%s' command does not take any arguments.\n",
-            m_cmd_name.c_str());
-        return false;
-      }
-
       if (m_options.m_ignore > 0) {
         ThreadSP sel_thread_sp(GetDefaultThread()->shared_from_this());
         if (sel_thread_sp) {
@@ -943,7 +930,10 @@ public:
   CommandObjectProcessConnect(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "process connect",
                             "Connect to a remote debug service.",
-                            "process connect <remote-url>", 0) {}
+                            "process connect <remote-url>", 0) {
+    CommandArgumentData connect_arg{eArgTypeConnectURL, eArgRepeatPlain};
+    m_arguments.push_back({connect_arg});
+  }
 
   ~CommandObjectProcessConnect() override = default;
 
@@ -1068,7 +1058,10 @@ public:
                             "process load <filename> [<filename> ...]",
                             eCommandRequiresProcess | eCommandTryTargetAPILock |
                                 eCommandProcessMustBeLaunched |
-                                eCommandProcessMustBePaused) {}
+                                eCommandProcessMustBePaused) {
+    CommandArgumentData file_arg{eArgTypePath, eArgRepeatPlus};
+    m_arguments.push_back({file_arg});
+  }
 
   ~CommandObjectProcessLoad() override = default;
 
@@ -1143,7 +1136,10 @@ public:
             "returned by a previous call to \"process load\".",
             "process unload <index>",
             eCommandRequiresProcess | eCommandTryTargetAPILock |
-                eCommandProcessMustBeLaunched | eCommandProcessMustBePaused) {}
+                eCommandProcessMustBeLaunched | eCommandProcessMustBePaused) {
+    CommandArgumentData load_idx_arg{eArgTypeUnsignedInteger, eArgRepeatPlain};
+    m_arguments.push_back({load_idx_arg});
+  }
 
   ~CommandObjectProcessUnload() override = default;
 
@@ -1291,18 +1287,13 @@ protected:
       return false;
     }
 
-    if (command.GetArgumentCount() == 0) {
-      bool clear_thread_plans = true;
-      Status error(process->Halt(clear_thread_plans));
-      if (error.Success()) {
-        result.SetStatus(eReturnStatusSuccessFinishResult);
-      } else {
-        result.AppendErrorWithFormat("Failed to halt process: %s\n",
-                                     error.AsCString());
-      }
+    bool clear_thread_plans = true;
+    Status error(process->Halt(clear_thread_plans));
+    if (error.Success()) {
+      result.SetStatus(eReturnStatusSuccessFinishResult);
     } else {
-      result.AppendErrorWithFormat("'%s' takes no arguments:\nUsage: %s\n",
-                                   m_cmd_name.c_str(), m_cmd_syntax.c_str());
+      result.AppendErrorWithFormat("Failed to halt process: %s\n",
+                                   error.AsCString());
     }
     return result.Succeeded();
   }
@@ -1330,17 +1321,12 @@ protected:
       return false;
     }
 
-    if (command.GetArgumentCount() == 0) {
-      Status error(process->Destroy(true));
-      if (error.Success()) {
-        result.SetStatus(eReturnStatusSuccessFinishResult);
-      } else {
-        result.AppendErrorWithFormat("Failed to kill process: %s\n",
-                                     error.AsCString());
-      }
+    Status error(process->Destroy(true));
+    if (error.Success()) {
+      result.SetStatus(eReturnStatusSuccessFinishResult);
     } else {
-      result.AppendErrorWithFormat("'%s' takes no arguments:\nUsage: %s\n",
-                                   m_cmd_name.c_str(), m_cmd_syntax.c_str());
+      result.AppendErrorWithFormat("Failed to kill process: %s\n",
+                                   error.AsCString());
     }
     return result.Succeeded();
   }
@@ -1372,7 +1358,10 @@ public:
             "appropriate file type.",
             "process save-core [-s corefile-style -p plugin-name] FILE",
             eCommandRequiresProcess | eCommandTryTargetAPILock |
-                eCommandProcessMustBeLaunched) {}
+                eCommandProcessMustBeLaunched) {
+    CommandArgumentData file_arg{eArgTypePath, eArgRepeatPlain};
+    m_arguments.push_back({file_arg});
+  }
 
   ~CommandObjectProcessSaveCore() override = default;
 
@@ -1519,11 +1508,6 @@ protected:
     Stream &strm = result.GetOutputStream();
     result.SetStatus(eReturnStatusSuccessFinishNoResult);
 
-    if (command.GetArgumentCount()) {
-      result.AppendError("'process status' takes no arguments");
-      return result.Succeeded();
-    }
-
     // No need to check "process" for validity as eCommandRequiresProcess
     // ensures it is valid
     Process *process = m_exe_ctx.GetProcessPtr();
diff --git a/lldb/source/Commands/CommandObjectQuit.cpp b/lldb/source/Commands/CommandObjectQuit.cpp
index c6e2e21..650cfca 100644
--- a/lldb/source/Commands/CommandObjectQuit.cpp
+++ b/lldb/source/Commands/CommandObjectQuit.cpp
@@ -20,7 +20,10 @@ using namespace lldb_private;
 
 CommandObjectQuit::CommandObjectQuit(CommandInterpreter &interpreter)
     : CommandObjectParsed(interpreter, "quit", "Quit the LLDB debugger.",
-                          "quit [exit-code]") {}
+                          "quit [exit-code]") {
+  CommandArgumentData exit_code_arg{eArgTypeUnsignedInteger, eArgRepeatPlain};
+  m_arguments.push_back({exit_code_arg});
+}
 
 CommandObjectQuit::~CommandObjectQuit() = default;
 
diff --git a/lldb/source/Commands/CommandObjectReproducer.cpp b/lldb/source/Commands/CommandObjectReproducer.cpp
index 31ed02f..8d12dec 100644
--- a/lldb/source/Commands/CommandObjectReproducer.cpp
+++ b/lldb/source/Commands/CommandObjectReproducer.cpp
@@ -182,12 +182,6 @@ public:
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (!command.empty()) {
-      result.AppendErrorWithFormat("'%s' takes no arguments",
-                                   m_cmd_name.c_str());
-      return false;
-    }
-
     auto &r = Reproducer::Instance();
     if (auto generator = r.GetGenerator()) {
       generator->Keep();
@@ -260,12 +254,6 @@ public:
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (!command.empty()) {
-      result.AppendErrorWithFormat("'%s' takes no arguments",
-                                   m_cmd_name.c_str());
-      return false;
-    }
-
     auto &r = Reproducer::Instance();
 
     if (!r.IsCapturing()) {
@@ -309,12 +297,6 @@ public:
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (!command.empty()) {
-      result.AppendErrorWithFormat("'%s' takes no arguments",
-                                   m_cmd_name.c_str());
-      return false;
-    }
-
     auto &r = Reproducer::Instance();
     if (r.IsCapturing()) {
       result.GetOutputStream() << "Reproducer is in capture mode.\n";
@@ -394,12 +376,6 @@ public:
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (!command.empty()) {
-      result.AppendErrorWithFormat("'%s' takes no arguments",
-                                   m_cmd_name.c_str());
-      return false;
-    }
-
     llvm::Optional<Loader> loader_storage;
     Loader *loader =
         GetLoaderFromPathOrCurrent(loader_storage, result, m_options.file);
diff --git a/lldb/source/Commands/CommandObjectSource.cpp b/lldb/source/Commands/CommandObjectSource.cpp
index 67286c2..f879818 100644
--- a/lldb/source/Commands/CommandObjectSource.cpp
+++ b/lldb/source/Commands/CommandObjectSource.cpp
@@ -538,14 +538,6 @@ protected:
   }
 
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    const size_t argc = command.GetArgumentCount();
-
-    if (argc != 0) {
-      result.AppendErrorWithFormat("'%s' takes no arguments, only flags.\n",
-                                   GetCommandName().str().c_str());
-      return false;
-    }
-
     Target *target = m_exe_ctx.GetTargetPtr();
     if (target == nullptr) {
       target = GetDebugger().GetSelectedTarget().get();
@@ -924,14 +916,6 @@ protected:
   }
 
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    const size_t argc = command.GetArgumentCount();
-
-    if (argc != 0) {
-      result.AppendErrorWithFormat("'%s' takes no arguments, only flags.\n",
-                                   GetCommandName().str().c_str());
-      return false;
-    }
-
     Target *target = m_exe_ctx.GetTargetPtr();
 
     if (!m_options.symbol_name.empty()) {
diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index 23ebbdb..2b71f1b 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -487,18 +487,14 @@ public:
 
 protected:
   bool DoExecute(Args &args, CommandReturnObject &result) override {
-    if (args.GetArgumentCount() == 0) {
-      Stream &strm = result.GetOutputStream();
+    Stream &strm = result.GetOutputStream();
 
-      bool show_stopped_process_status = false;
-      if (DumpTargetList(GetDebugger().GetTargetList(),
-                         show_stopped_process_status, strm) == 0) {
-        strm.PutCString("No targets.\n");
-      }
-      result.SetStatus(eReturnStatusSuccessFinishResult);
-    } else {
-      result.AppendError("the 'target list' command takes no arguments\n");
+    bool show_stopped_process_status = false;
+    if (DumpTargetList(GetDebugger().GetTargetList(),
+                       show_stopped_process_status, strm) == 0) {
+      strm.PutCString("No targets.\n");
     }
+    result.SetStatus(eReturnStatusSuccessFinishResult);
     return result.Succeeded();
   }
 };
@@ -511,6 +507,8 @@ public:
       : CommandObjectParsed(
             interpreter, "target select",
             "Select a target as the current target by target index.", nullptr) {
+    CommandArgumentData target_arg{eArgTypeTargetID, eArgRepeatPlain};
+    m_arguments.push_back({target_arg});
   }
 
   ~CommandObjectTargetSelect() override = default;
@@ -575,6 +573,8 @@ public:
     m_option_group.Append(&m_all_option, LLDB_OPT_SET_ALL, LLDB_OPT_SET_1);
     m_option_group.Append(&m_cleanup_option, LLDB_OPT_SET_ALL, LLDB_OPT_SET_1);
     m_option_group.Finalize();
+    CommandArgumentData target_arg{eArgTypeTargetID, eArgRepeatStar};
+    m_arguments.push_back({target_arg});
   }
 
   ~CommandObjectTargetDelete() override = default;
@@ -1230,10 +1230,6 @@ public:
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
     Target *target = &GetSelectedTarget();
-    if (command.GetArgumentCount() != 0) {
-      result.AppendError("list takes no arguments\n");
-      return result.Succeeded();
-    }
 
     target->GetImageSearchPathList().Dump(&result.GetOutputStream());
     result.SetStatus(eReturnStatusSuccessFinishResult);
@@ -2454,6 +2450,8 @@ public:
                           LLDB_OPT_SET_1);
     m_option_group.Append(&m_symbol_file, LLDB_OPT_SET_ALL, LLDB_OPT_SET_1);
     m_option_group.Finalize();
+    CommandArgumentData module_arg{eArgTypePath, eArgRepeatStar};
+    m_arguments.push_back({module_arg});
   }
 
   ~CommandObjectTargetModulesAdd() override = default;
@@ -4019,6 +4017,8 @@ public:
     m_option_group.Append(&m_current_stack_option, LLDB_OPT_SET_2,
                           LLDB_OPT_SET_2);
     m_option_group.Finalize();
+    CommandArgumentData module_arg{eArgTypeShlibName, eArgRepeatPlain};
+    m_arguments.push_back({module_arg});
   }
 
   ~CommandObjectTargetSymbolsAdd() override = default;
@@ -4867,7 +4867,10 @@ public:
   CommandObjectTargetStopHookDelete(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "target stop-hook delete",
                             "Delete a stop-hook.",
-                            "target stop-hook delete [<idx>]") {}
+                            "target stop-hook delete [<idx>]") {
+    CommandArgumentData hook_arg{eArgTypeStopHookID, eArgRepeatStar};
+    m_arguments.push_back({hook_arg});
+  }
 
   ~CommandObjectTargetStopHookDelete() override = default;
 
@@ -4921,6 +4924,8 @@ public:
                                            bool enable, const char *name,
                                            const char *help, const char *syntax)
       : CommandObjectParsed(interpreter, name, help, syntax), m_enable(enable) {
+    CommandArgumentData hook_arg{eArgTypeStopHookID, eArgRepeatStar};
+    m_arguments.push_back({hook_arg});
   }
 
   ~CommandObjectTargetStopHookEnableDisable() override = default;
@@ -4976,8 +4981,7 @@ class CommandObjectTargetStopHookList : public CommandObjectParsed {
 public:
   CommandObjectTargetStopHookList(CommandInterpreter &interpreter)
       : CommandObjectParsed(interpreter, "target stop-hook list",
-                            "List all stop-hooks.",
-                            "target stop-hook list [<type>]") {}
+                            "List all stop-hooks.", "target stop-hook list") {}
 
   ~CommandObjectTargetStopHookList() override = default;
 
@@ -5049,11 +5053,6 @@ public:
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
-    if (!command.empty()) {
-      result.AppendError("target dump typesystem doesn't take arguments.");
-      return result.Succeeded();
-    }
-
     // Go over every scratch TypeSystem and dump to the command output.
     for (TypeSystem *ts : GetSelectedTarget().GetScratchTypeSystems())
       ts->Dump(result.GetOutputStream().AsRawOstream());
diff --git a/lldb/source/Commands/CommandObjectThreadUtil.cpp b/lldb/source/Commands/CommandObjectThreadUtil.cpp
index d330da7..cac1bef 100644
--- a/lldb/source/Commands/CommandObjectThreadUtil.cpp
+++ b/lldb/source/Commands/CommandObjectThreadUtil.cpp
@@ -19,7 +19,11 @@ using namespace llvm;
 CommandObjectIterateOverThreads::CommandObjectIterateOverThreads(
     CommandInterpreter &interpreter, const char *name, const char *help,
     const char *syntax, uint32_t flags)
-    : CommandObjectParsed(interpreter, name, help, syntax, flags) {}
+    : CommandObjectParsed(interpreter, name, help, syntax, flags) {
+  // These commands all take thread ID's as arguments.
+  CommandArgumentData thread_arg{eArgTypeThreadIndex, eArgRepeatStar};
+  m_arguments.push_back({thread_arg});
+}
 
 bool CommandObjectIterateOverThreads::DoExecute(Args &command,
                                                 CommandReturnObject &result) {
diff --git a/lldb/source/Commands/CommandObjectTrace.cpp b/lldb/source/Commands/CommandObjectTrace.cpp
index 2fa68f1..17aded9 100644
--- a/lldb/source/Commands/CommandObjectTrace.cpp
+++ b/lldb/source/Commands/CommandObjectTrace.cpp
@@ -75,7 +75,10 @@ public:
       : CommandObjectParsed(
             interpreter, "trace load",
             "Load a post-mortem processor trace session from a trace bundle.",
-            "trace load") {}
+            "trace load") {
+    CommandArgumentData session_file_arg{eArgTypePath, eArgRepeatPlain};
+    m_arguments.push_back({session_file_arg});
+  }
 
   ~CommandObjectTraceLoad() override = default;
 
@@ -223,7 +226,10 @@ public:
       : CommandObjectParsed(interpreter, "trace schema",
                             "Show the schema of the given trace plugin.",
                             "trace schema <plug-in>. Use the plug-in name "
-                            "\"all\" to see all schemas.\n") {}
+                            "\"all\" to see all schemas.\n") {
+    CommandArgumentData plugin_arg{eArgTypeNone, eArgRepeatPlain};
+    m_arguments.push_back({plugin_arg});
+  }
 
   ~CommandObjectTraceSchema() override = default;
 
diff --git a/lldb/source/Commands/CommandObjectType.cpp b/lldb/source/Commands/CommandObjectType.cpp
index b79c19b..3ad3571 100644
--- a/lldb/source/Commands/CommandObjectType.cpp
+++ b/lldb/source/Commands/CommandObjectType.cpp
@@ -914,7 +914,10 @@ public:
                                   uint32_t formatter_kind_mask,
                                   const char *name, const char *help)
       : CommandObjectParsed(interpreter, name, help, nullptr),
-        m_formatter_kind_mask(formatter_kind_mask) {}
+        m_formatter_kind_mask(formatter_kind_mask) {
+    CommandArgumentData category_arg{eArgTypeName, eArgRepeatOptional};
+    m_arguments.push_back({category_arg});
+  }
 
   ~CommandObjectTypeFormatterClear() override = default;
 
diff --git a/lldb/source/Commands/CommandObjectVersion.cpp b/lldb/source/Commands/CommandObjectVersion.cpp
index e15faba..9b3c9e6 100644
--- a/lldb/source/Commands/CommandObjectVersion.cpp
+++ b/lldb/source/Commands/CommandObjectVersion.cpp
@@ -23,11 +23,7 @@ CommandObjectVersion::CommandObjectVersion(CommandInterpreter &interpreter)
 CommandObjectVersion::~CommandObjectVersion() = default;
 
 bool CommandObjectVersion::DoExecute(Args &args, CommandReturnObject &result) {
-  if (args.GetArgumentCount() == 0) {
-    result.AppendMessageWithFormat("%s\n", lldb_private::GetVersion());
-    result.SetStatus(eReturnStatusSuccessFinishResult);
-  } else {
-    result.AppendError("the version command takes no arguments.");
-  }
+  result.AppendMessageWithFormat("%s\n", lldb_private::GetVersion());
+  result.SetStatus(eReturnStatusSuccessFinishResult);
   return true;
 }