642987 - PyXPCOM should allow callabales to be used as [function] interfaces

Status: RESOLVED FIXED

(Other Applications Graveyard :: PyXPCOM, defect)

Description

[Mook (work)]

Attachment: support [function]

See attached patch.  Interfaces marked as [function] (such as nsIDOMEventListener) can be implemented in JavaScript as functions; this patch does the equivalent for Python.

Not quite sure the patch is good enough as-is, particularly since I have yet to figure out how unit testing works in this area of code.

Comment 1

[Todd Whiteman]

Any ideas for a test case on this? As I'm still not sure how callables are meant to be used.

Comment 2

[Mook (work)]

  called = False

  def observe(subject, topic, data):
    called = True

  sip = components.classes["@mozilla.org/supports-interface-pointer;1"]\
                  .createInstance(components.interfaces\
                                            .nsISupportsInterfacePointer)
  sip.data = observe
  sip.data.QueryInterface(components.interferfaces.nsIObserver)\
          .observe(None, "topic", None)
  assert(called)

Basically, it makes it possible to pass in Python functions in places where things like nsIObserver (and other XPCOM interfaces marked as [function]) are expected.  (In this case, of course, actually hooking it up to nsIObserverService or something would be the typical use case)

Comment 3

[Todd Whiteman]

This needs a isfunction check - because I could also have a class that implements __call__, then if I was using a class instance in this case it would trigger the __call__ method, instead of the class instance method.

Comment 4

[Mook (work)]

Comment on attachment 520309 [details] [diff] [review]
support [function]

Hrm. This got checked in in https://hg.mozilla.org/pyxpcom/rev/f4a3b01293f5 for some reason.  Poked around more, fixed up in https://hg.mozilla.org/pyxpcom/rev/67a18ad95aab in cases where we have:

  class Foo(object):
    _com_interfaces_ = [components.interfaces.nsIObserver]
    def observe(self, s, t, d):
      print("observe")
    def __call__(self, *args):
      print "should not call me")
  sip.data = Foo()
  sip.data.QueryInterface(components.interfaces.nsIObserver).observe(None, "", "")

(It would previously prefer __call__ when *calling* things that are not getters/setters; it now only uses it if the named method doesn't exist.)