[lldb] Fix completion of 'settings set' values

[kastiglione]

Summary

Some time ago, a refactor (1153dc960) broke completion for assigning settings
values (settings set). This was most annoying for enum settings, where you'd
have to get the valid enum names separately.

This restores the logic in the post-refactor completion function, as well as
adding a test to catch future regressions.

[DavidSpickett]

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

409

settings

410

Could you add to the comment why this one was chosen in particular? Something like:

Checks that we can complete a setting that has enum values.

Since there is a settings set test above but clearly that wasn't enough coverage.

[DavidSpickett]

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

409

And these comments are rather redundant but it's the local style so it's fine to stick with it.

[kastiglione]

Rename test and change the docstring to be meaningful.

[kastiglione]

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

410

done, I also renamed the test to describe why not what.

[kastiglione]

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

410

correction: to describe what, not how.

[DavidSpickett]

LGTM, thanks for the fix!

lldb/source/Commands/CommandObjectSettings.cpp

if (request.GetCursorIndex() == setting_var_idx) {
       return;
     }
     arg = request.GetParsedLine().GetArgumentAtIndex(request.GetCursorIndex());
 
     if (!arg)
       return;
 
     // Complete option name
-    if (arg[0] != '-')
+    if (arg[0] == '-')
       return;
 
     // Complete setting value
     const char *setting_var_name =
         request.GetParsedLine().GetArgumentAtIndex(setting_var_idx);
     Status error;
     lldb::OptionValueSP value_sp(GetDebugger().GetPropertyValue(
         &m_exe_ctx, setting_var_name, false, error));

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

class CommandLineCompletionTestCase(TestBase):
 
     def test_settings_set_target_process_thread_dot(self):
         """Test that 'settings set target.process.thread.' completes to [
         'target.process.thread.step-avoid-regexp', 'target.process.thread.trace-thread']."""
         self.complete_from_to('settings set target.process.thread.',
                               ['target.process.thread.step-avoid-regexp',
                                'target.process.thread.trace-thread'])
 
+    def test_settings_set_can_complete_setting_enum_values(self):
+        """Checks that we can complete the values of an enum setting."""
+        self.complete_from_to('settings set stop-disassembly-display ',
+                              ['never', 'always', 'no-debuginfo', 'no-source'])
+
     def test_thread_plan_discard(self):
         self.build()
         (_, _, thread, _) = lldbutil.run_to_source_breakpoint(self,
                                           'ptr_foo', lldb.SBFileSpec("main.cpp"))
         self.assertTrue(thread)
         self.complete_from_to('thread plan discard ', 'thread plan discard ')
 
         source_path = os.path.join(self.getSourceDir(), "thread_plan_script.py")