interface: Don't mutate user options

This patch fixes cases where the 'opts' table passed by the user is
modified, making the external table unable to be reused in some
cases.

This was causing problems e.g. when dealing with properties, as the
user was having a predefined dbus options table, as the "interface"
key was changed internally to 'org.freedesktop.DBus.Properties'
without being changed back on return.

Author: Rafael Gago

init.lua

@@ -17,6 +17,22 @@ else
     dbus.exit = dbus.raw.exit
 end
 
+local function optscopy(opts)
+    if type(opts) ~= "table" then return nil end
+    return {
+        args = opts.args,
+        bus = opts.bus,
+        callback = opts.callback,
+        destination = opts.destination,
+        handler = opts.handler,
+        interface = opts.interface,
+        origin = opts.origin,
+        path = opts.path,
+        sender = opts.sender,
+        type = opts.type,
+    }
+end
+
 function dbus.signal_handler(signal, ...)
     signal.events = ((dbus.signals[signal.bus] or {})[signal.interface] or {}).events
     if not signal.events then return end
@@ -58,7 +74,7 @@ function dbus.on(name, callback, opts)
     elseif callback and type(callback) ~= 'function' then
         callback, opts = nil, callback
     end
-    opts = opts or {}
+    local opts = optscopy(opts) or {}
     opts.type = opts.type or "signal"
     opts.bus = opts.bus or "session"
     callback = callback or opts.callback
@@ -115,7 +131,7 @@ end
 
 
 function dbus.off(name, callback, opts)
-    opts = opts or {}
+    local opts = optscopy(opts) or {}
     opts.type = opts.type or "signal"
     opts.bus = opts.bus or "session"
     local signal = (dbus.signals[opts.bus] or {})[opts.interface]
@@ -156,7 +172,7 @@ function dbus.call(name, callback, opts)
     if callback and type(callback) ~= 'function' then
         callback, opts = nil, callback
     end
-    opts = opts or {}
+    local opts = optscopy(opts) or {}
     opts.type = opts.type or "method_call"
     opts.bus = opts.bus or "session"
     callback = callback or opts.callback
@@ -179,9 +195,8 @@ function dbus.call(name, callback, opts)
     return serial
 end
 
-
 function dbus.property.get(name, callback, opts)
-    opts = opts or {}
+    local opts = optscopy(opts) or {}
     opts.args = {'s', opts.interface, 's', name} -- actual arguments to Get
     opts.interface = 'org.freedesktop.DBus.Properties'
     callback = callback or opts.callback
@@ -190,7 +205,7 @@ end
 
 
 function dbus.property.set(name, value, opts)
-    opts = opts or {}
+    local opts = optscopy(opts) or {}
     opts.args = {'s', opts.interface, 's', name, 'v', value} -- actual arguments to Get
     opts.interface = 'org.freedesktop.DBus.Properties'
     return dbus.call('Set', opts)