The following snippet causes an exception to be raised in Marionette: retval = self.marionette.execute_script(""" return arguments[1]; """, script_args=['test', None]) assert retval is None Exception: Traceback (most recent call last): File "/mozilla/code/firefox/inbound/testing/marionette/client/marionette/marionette_test.py", line 268, in run testMethod() File "/mozilla/code/marionette-tests/greenlight/lib/tests/test_prefs.py", line 36, in test_get_pref """, script_args=['test', None]) File "/mozilla/code/firefox/inbound/testing/marionette/client/marionette/marionette.py", line 1282, in execute_script filename=os.path.basename(frame[0])) File "/mozilla/code/firefox/inbound/testing/marionette/client/marionette/decorators.py", line 36, in _ return func(*args, **kwargs) File "/mozilla/code/firefox/inbound/testing/marionette/client/marionette/marionette.py", line 634, in _send_message self._handle_error(response) File "/mozilla/code/firefox/inbound/testing/marionette/client/marionette/marionette.py", line 663, in _handle_error "Malformed packet, expected key 'error' to be a dict: %s" % response) MarionetteException: MarionetteException: Malformed packet, expected key 'error' to be a dict: {u'message': u'arg is null', u'error': u"error occurred while processing 'executeScript"} Instead None should become undefined in Javascript, and returned as None again.

I would expect None to map to null. I think this function just needs a null check: https://hg.mozilla.org/mozilla-central/file/7507dfe42c11/testing/marionette/marionette-elements.js#l384

Ah, you are right. null is indeed the better value here.

Actually, applyNamedArgs functionality doesn't look like it's used anywhere. :jgriffin, do you happen to know if this is used or what we should do with it?

applyNamedArgs is used to pass element references between calls on the Python side. So you can do something like: button = marionette.find_element('id', 'foo') print button >>> # some uuid marionette.execute_script("arguments[0].click();", script_args=button)

(In reply to Jonathan Griffin (:jgriffin) from comment #4) > applyNamedArgs is used to pass element references between calls on the > Python side. So you can do something like: > > button = marionette.find_element('id', 'foo') > print button > >>> # some uuid > marionette.execute_script("arguments[0].click();", script_args=button) ...and I realize that doesn't answer your question. I think we don't use applyNamedArgs any longer; we used to use it in some idiosyncratic B2G frameworks that don't exist any longer, as in: https://hg.mozilla.org/mozilla-central/annotate/e934a9d8be1f/testing/marionette/client/marionette/marionette_test.py#l165

/r/2205 - Bug 1118825 - Allow passing None as an argument to executeScript in chrome scope.;r=ato Pull down this commit: hg pull review -r 83cb0b0c1a631eccec9559d5fc8b088f279d24a0

/r/2205 - Bug 1118825 - Allow passing None as an argument to executeScript in chrome scope.;r=ato Pull down this commit: hg pull review -r 83cb0b0c1a631eccec9559d5fc8b088f279d24a0

https://reviewboard.mozilla.org/r/2203/#review1651 Ship It!

Works fine. Thanks!