awful.remote: Run code in a protected context (#2203)

This change makes errors messages show up in the replies, too.

Before (notice how the third command does not generate output):

$ awesome-client 'return 42' ; awesome-client 'sdfsdf' ; awesome-client 'error("foo")'
   double 42
   string "[string "sdfsdf"]:1: syntax error near <eof>"

After:

$ awesome-client 'return 42' ; awesome-client 'sdfsdf' ; awesome-client 'error("foo")'
   double 42
   string "[string "sdfsdf"]:1: syntax error near <eof>"
   string "Error during execution: [string "error("foo")"]:1: foo"

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/awful/remote.lua

@@ -20,8 +20,13 @@ if dbus then
     dbus.connect_signal("org.awesomewm.awful.Remote", function(data, code)
         if data.member == "Eval" then
             local f, e = load(code)
-            if f then
+            if not f then
-                local results = { f() }
+                return "s", e
+            end
+            local results = { pcall(f) }
+            if not table.remove(results, 1) then
+                return "s", "Error during execution: " .. results[1]
+            end
             local retvals = {}
             for _, v in ipairs(results) do
                 local t = type(v)
@@ -37,9 +42,6 @@ if dbus then
                 end
             end
             return unpack(retvals)
-            elseif e then
-                return "s", e
-            end
         end
     end)
 end