Lua prompt improvements

From awesome

The default Lua prompt (Mod+F4) can be a bit awkward to use. These two hacks allow adding both auto-completion and better evaluation support.

[edit] Completion

(by espenhw)

This isn't very useful, maybe, but it's kinda cool that it is even possible!

Use this function as the completion_callback argument to awful.prompt.run.

function lua_completion (line, cur_pos, ncomp)
   -- Only complete at the end of the line, for now
   if cur_pos ~= #line + 1 then
      return line, cur_pos
   end

   -- We're really interested in the part following the last (, [, comma or space
   local lastsep = #line - (line:reverse():find('[[(, ]') or #line)
   local lastidentifier
   if lastsep ~= 0 then
      lastidentifier = line:sub(lastsep + 2)
   else
      lastidentifier = line
   end

   local environment = _G

   -- String up to last dot is our current environment
   local lastdot = #lastidentifier - (lastidentifier:reverse():find('.', 1, true) or #lastidentifier)
   if lastdot ~= 0 then
      -- We have an environment; for each component in it, descend into it
      for env in lastidentifier:sub(1, lastdot):gmatch('([^.]+)') do
         if not environment[env] then
            -- Oops, no such subenvironment, bail out
            return line, cur_pos
         end
         environment = environment[env]
      end
   end

   local tocomplete = lastidentifier:sub(lastdot + 1)
   if tocomplete:sub(1, 1) == '.' then
      tocomplete = tocomplete:sub(2)
   end

   local completions = {}
   for k, v in pairs(environment) do
      if type(k) == "string" and k:sub(1, #tocomplete) == tocomplete then
         table.insert(completions, k)
      end
   end

   if #completions == 0 then
      return line, cur_pos
   end
   
   while ncomp > #completions do
      ncomp = ncomp - #completions
   end

   local str = ""
   if lastdot + lastsep ~= 0 then
      str = line:sub(1, lastsep + lastdot + 1)
   end
   str = str .. completions[ncomp]
   cur_pos = #str + 1
   return str, cur_pos
end

[edit] Evaluation

(by MattJ)

This eval function improves the default awful.util.eval for the Lua prompt to show the result of an execution, either return value(s) or an error. It also executes the code in the same context as your rc.lua, meaning you can access widgets and variables created there.

To use, simply add this function to your rc.lua, above where the Lua prompt is created. Change awful.util.eval on the prompt line to usefuleval.

function usefuleval(s)
	local f, err = loadstring("return "..s);
	if not f then
		f, err = loadstring(s);
	end
	
	if f then
		setfenv(f, _G);
		local ret = { pcall(f) };
		if ret[1] then
			-- Ok
			table.remove(ret, 1)
			local highest_index = #ret;
			for k, v in pairs(ret) do
				if type(k) == "number" and k > highest_index then
					highest_index = k;
				end
				ret[k] = select(2, pcall(tostring, ret[k])) or "<no value>";
			end
			-- Fill in the gaps
			for i = 1, highest_index do
				if not ret[i] then
					ret[i] = "nil"
				end
			end
			if highest_index > 0 then
				mypromptbox[mouse.screen].text = awful.util.escape("Result"..(highest_index > 1 and "s" or "")..": "..tostring(table.concat(ret, ", ")));
			else
				mypromptbox[mouse.screen].text = "Result: Nothing";
			end
		else
			err = ret[2];
		end
	end
	if err then
		mypromptbox[mouse.screen].text = awful.util.escape("Error: "..tostring(err));
	end
end