only call layouts that are callable in uzful.layout.build

layout/util.lua

@@ -7,6 +7,7 @@
 local util = {}
 
 local tag = require("awful.tag")
+local uzful = { util = require("uzful.util") }
 
 
 --- Builds a layout from a table tree
@@ -16,17 +17,16 @@ local tag = require("awful.tag")
 -- @param tree the table describing the layout (can be recursive)
 -- @return a layout or the result of the given function or just the input
 function util.build(tree)
+    if not tree then return end
     if type(tree) == "function" then
         return tree()
     end
-    if tree.layout then
+    if uzful.util.iscallable(tree.layout) then
         local value = nil
         local layout = tree.layout()
         for i=1,#tree do
-            if tree[i] then
-                value = util.build(tree[i])
-                if value then layout:add(value) end
-            end
+            value = util.build(tree[i])
+            if value then layout:add(value) end
         end
         for key, value in pairs(tree) do
             if type(key) == "string" and layout["set_" .. key] then

util.lua

@@ -312,5 +312,13 @@ function util.lineswrap(s, n)
     return table.concat(lines, "\n")
 end
 
+function util.iscallable(object)
+    if not object then return false end
+    if type(object) == 'function' then return true end
+    local metatable = getmetatable(object)
+    if metatable and metatable.__call then return true end
+    return false
+end
+
 
 return util