[core.app] Use `equal' to compare configurations.

src/core/app.lua

@@ -42,6 +42,22 @@ function configure (new_config)
    configuration = new_config
 end
 
+-- Returns true if x and y are structurally similar (isomorphic).
+function equal (x, y)
+   if type(x) ~= type(y) then return false end
+   if type(x) == 'table' then
+      for k, v in pairs(x) do
+         if not equal(v, y[k]) then return false end
+      end
+      for k, _ in pairs(x) do
+         if y[k] == nil then return false end
+      end
+      return true
+   else
+      return x == y
+   end
+end
+
 -- Return the configuration actions needed to migrate from old config to new.
 -- The return value is a table:
 --   app_name -> stop | start | keep | restart | reconfig
@@ -52,8 +68,8 @@ function compute_config_actions (old, new)
       local action = nil
       if not old.apps[appname]                then action = 'start'
       elseif old.apps[appname].class ~= class then action = 'restart'
-      elseif (type(old.apps[appname].arg) == "string" and
-	   old.apps[appname].arg ~= arg)      then action = 'reconfig'
+      elseif not equal(old.apps[appname].arg, arg)
+                                              then action = 'reconfig'
       else                                         action = 'keep'  end
       actions[appname] = action
    end