Improve error handling for `f s #`

[amccarth]

Summary

When there were too many arguments given for the frame select command, the error message wasn't particularly helpful and then lldb would try to select frame -1, which resulted in an additional confusing error message.

This happened when the user expects f s 1 to be a short form of frame select 1, but the f itself is an alias for frame select, so the s is extraneous.

The new output should make it easier for the user to understand what went wrong:

(lldb) f s 1
error: too many arguments; expect frame-index, saw 's'.

Command Options Usage:

frame select [-r <offset>] [<frame-index>]

     -r <offset> ( --relative <offset> )
          A relative frame index offset from the current frame index.

[emaste]

LGTM
Or if you want show the set of arguments - e.g. expected frame-index, got 's 1' That might clarify the "too many arguments."

[Eugene.Zelenko]

Committed in r256251. Please specify Differential revision in commit message.

packages/Python/lldbsuite/test/functionalities/abbreviation/TestCommonShortSpellings.py

def test_abbrevs2 (self):
 
         abbrevs = [
             ('br s', 'breakpoint set'),
             ('disp', '_regexp-display'),  # a.k.a., 'display'
             ('di', 'disassemble'),
             ('dis', 'disassemble'),
             ('ta st a', 'target stop-hook add'),
             ('fr v', 'frame variable'),
+            ('f 1', 'frame select 1'),
             ('ta st li', 'target stop-hook list'),
         ]
 
         for (short_val, long_val) in abbrevs:
             command_interpreter.ResolveCommand(short_val, result)
             self.assertTrue(result.Succeeded())
             self.assertEqual(long_val, result.GetOutput())

source/Commands/CommandObjectFrame.cpp

DoExecute (Args& command, CommandReturnObject &result) override
                 frame_idx = thread->GetSelectedFrameIndex ();
                 if (frame_idx == UINT32_MAX)
                 {
                     frame_idx = 0;
                 }
             }
             else
             {
-                result.AppendError ("invalid arguments.\n");
+                result.AppendErrorWithFormat ("too many arguments; expected frame-index, saw '%s'.\n",
+                                              command.GetArgumentAtIndex(0));
                 m_options.GenerateOptionUsage (result.GetErrorStream(), this);
+                return false;
             }
         }
 
         bool success = thread->SetSelectedFrameByIndexNoisily (frame_idx, result.GetOutputStream());
         if (success)
         {
             m_exe_ctx.SetFrameSP(thread->GetSelectedFrame ());
             result.SetStatus (eReturnStatusSuccessFinishResult);