[lldb] Tab completion for `frame select`

[MrHate]

Summary

Provided the tab completion for command frame select.

[MrHate]

Removed one redundant newline in TestCompletion.py.

[teemperor]

LGTM

lldb/source/Commands/CommandObjectFrame.cpp

CommandObjectFrameSelect(CommandInterpreter &interpreter)
     arg.push_back(index_arg);
 
     // Push the data for the first argument into the m_arguments vector.
     m_arguments.push_back(arg);
   }
 
   ~CommandObjectFrameSelect() override = default;
 
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
+    if (!m_exe_ctx.HasProcessScope() || request.GetCursorIndex() != 0)
+      return;
+
+    lldb::ThreadSP thread_sp = m_exe_ctx.GetThreadSP();
+    const uint32_t frame_num = thread_sp->GetStackFrameCount();
+    for (uint32_t i = 0; i < frame_num; ++i) {
+      lldb::StackFrameSP frame_sp = thread_sp->GetStackFrameAtIndex(i);
+      StreamString strm;
+      frame_sp->Dump(&strm, false, true);
+      request.TryCompleteCurrentArg(std::to_string(i), strm.GetString());
+    }
+  }
+
   Options *GetOptions() override { return &m_options; }
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
     // No need to check "thread" for validity as eCommandRequiresThread ensures
     // it is valid
     Thread *thread = m_exe_ctx.GetThreadPtr();
 

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

def test_completion_description_command_options(self):
             ["--on-catch", "Set the breakpoint on exception catcH."],
             ["--on-throw", "Set the breakpoint on exception throW."]
         ])
 
         # Unknown long option.
         self.check_completion_with_desc("breakpoint set --Z", [
         ])
 
+    def test_frame_select(self):
+        self.build()
+        self.main_source_spec = lldb.SBFileSpec("main.cpp")
+        lldbutil.run_to_source_breakpoint(self, '// Break here', self.main_source_spec)
+
+        self.complete_from_to('frame select ', ['0'])
+
+
     @expectedFailureAll(oslist=["windows"], bugnumber="llvm.org/pr24489")
     def test_symbol_name(self):
         self.build()
         self.dbg.CreateTarget(self.getBuildArtifact("a.out"))
         self.complete_from_to('breakpoint set -n Fo',
                               'breakpoint set -n Foo::Bar(int,\\ int)',
                               turn_off_re_match=True)
         # No completion for Qu because the candidate is