Expression autocompletion with variables and symbols

[acoomans]

Summary

This adds autocompletion for the expression (and thus print and p) commands. Variables and symbols are suggested.

For example: let's assume we have a struct called my_struct. We break, then run:

(lldb) p my_ [TAB]

will autocomplete to:

(lldb) p my_struct

Now let's assume we run:

(lldb) p m [TAB]

we'll get suggestions from all corresponding symbols like this:

Available completions:
	mach_absolute_time
	mach_approximate_time
	mach_boottime_usec
	mach_continuous_approximate_time
	mach_continuous_time
	mach_error
[...]
More (Y/n/a):

[teemperor]

I think D48465 is doing the same thing (and more).

[acoomans]

@teemperor Nice. Looks like you're way ahead of me. I'll abandon this. Let me know if you want help with your code!

[teemperor]

@acoomans D48465 has landed, so feel free to file bugs for any completions that are not provided by this. Thanks!

source/Commands/CommandObjectExpression.h

public:
   };
 
   CommandObjectExpression(CommandInterpreter &interpreter);
 
   ~CommandObjectExpression() override;
 
   Options *GetOptions() override;
 
+  int HandleArgumentCompletion(CompletionRequest &request, OptionElementVector &opt_element_vector) override;
+
 protected:
   //------------------------------------------------------------------
   // IOHandler::Delegate functions
   //------------------------------------------------------------------
   void IOHandlerInputComplete(IOHandler &io_handler,
                               std::string &line) override;
 
   bool IOHandlerIsInputComplete(IOHandler &io_handler,
                                 StringList &lines) override;
 
   bool DoExecute(llvm::StringRef command, CommandReturnObject &result) override;
 
   bool EvaluateExpression(llvm::StringRef expr, Stream *output_stream,
                           Stream *error_stream,
                           CommandReturnObject *result = NULL);
 
   void GetMultilineExpression();
 
+    bool WantsRawCommandString() override { return false; }
+
   OptionGroupOptions m_option_group;
   OptionGroupFormat m_format_options;
   OptionGroupValueObjectDisplay m_varobj_options;
   OptionGroupBoolean m_repl_option;
   CommandOptions m_command_options;
   uint32_t m_expr_line_count;
   std::string m_expr_lines;       // Multi-line expression support
   std::string m_fixed_expression; // Holds the current expression's fixed text.
 };
 
 } // namespace lldb_private
 
 #endif // liblldb_CommandObjectExpression_h_

source/Commands/CommandObjectExpression.cpp

Examples:
   m_option_group.Append(&m_repl_option, LLDB_OPT_SET_ALL, LLDB_OPT_SET_3);
   m_option_group.Finalize();
 }
 
 CommandObjectExpression::~CommandObjectExpression() = default;
 
 Options *CommandObjectExpression::GetOptions() { return &m_option_group; }
 
+int CommandObjectExpression::HandleArgumentCompletion(CompletionRequest &request,
+                                                      OptionElementVector &opt_element_vector)   {
+  CommandCompletions::InvokeCommonCompletionCallbacks(
+          GetCommandInterpreter(),
+          CommandCompletions::eVariablePathCompletion | CommandCompletions::eSymbolCompletion,
+          request,
+          nullptr);
+  return request.GetNumberOfMatches();
+}
+
 static lldb_private::Status
 CanBeUsedForElementCountPrinting(ValueObject &valobj) {
   CompilerType type(valobj.GetCompilerType());
   CompilerType pointee;
   if (!type.IsPointerType(&pointee))
     return Status("as it does not refer to a pointer");
   if (pointee.IsVoidType())
     return Status("as it refers to a pointer to void");