[Zope-dev] Bug in ExternalMethods?
Hi Tim,
> Here's a small demonstration of the bug:
>
> --test.py--
> def test(self, a_string, an_int, a_named_arg=1):
> """bug provoking?"""
> template = """a_string = %s; type(a_string) -> %s\n
> an_int = %s; type(an_int) -> %s\n
> a_named_arg = %s; type(a_named_arg) -> %s"""
> return template % (a_string, type(a_string), an_int, type(an_int),
> a_named_arg, type(a_named_arg))
>
External methods need no "self" (and normally should have no "self") as
first parameter, as they are not methods of some objects, I thought.
But Zope seems to do some magic here.
>
> --Script (Python)--
> return container.test('tim', 10, a_named_arg=(1,1))
> return container.test('tim', 10, (1,1))
>
>
Indeed the first call should be illegal, as one passes only two
non-keyword arguments, but the function has three arguments without
default values. If I try to call the function from the python
command line in an equivalent way as done here by the script, I get an
TypeError: test() takes at least 3 non-keyword arguments (2 given).
But Zope seems to mangle in the container/context into the "self" argument,
if the following two conditions hold:
1. the first argument is named "self".
(If the first argument is named "foo", it does not work.)
2. there are to less arguments to make a "normal" function call
Condition 2. is true for the first call, but not for the second one.
Here enough arguments are provided to make a plaing function call
with the arguments:
self='tim', a_string=10, an_int=(1,1), a_named_arg=(1,1),
as defined by the caller or the default values.
Thus I guess it is not a bug, but a feature. There is actually an
example for this usage in the Zope Book (with the image thumbnails), but
at least I failed to recognise the magic "self" mumble.
Cheers,
Clemens
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Re: [Zope-dev] Bug in ExternalMethods?
Tim Hicks writes:
> I think I've found a bug in ExternalMethod, but I don't know if it's
> already been fixed or not.
>
> Basically, the call signature of ExternalMethods seems to get mixed up
> sometimes. I'm running Zope 2.5.1 on Linux.
>
> Here's a small demonstration of the bug:
>
> --test.py--
> def test(self, a_string, an_int, a_named_arg=1):
> """bug provoking?"""
> template = """a_string = %s; type(a_string) -> %s\n
> an_int = %s; type(an_int) -> %s\n
> a_named_arg = %s; type(a_named_arg) -> %s"""
> return template % (a_string, type(a_string), an_int, type(an_int),
> a_named_arg, type(a_named_arg))
>
>
> --Script (Python)--
> return container.test('tim', 10, a_named_arg=(1,1))
> return container.test('tim', 10, (1,1))
>
>
> You can see the dodgy behaviour by switching between the two test() calls
> in the Script (Python).
This is not a bug but a documented "feature".
The automatic "self" passing magic only happens when you
call the method with one positional argument less than required.
(This does not apply to ZPublisher which uses a different way.)
Your External Method has 3 required and one optional argument.
In your first case, you pass 2 required positional arguments
and give the optional a different value. As one required positional
argument is missing, "self" is passed in automatically.
In your second case, you pass 3 required positional arguments.
"self" is not passed in automatically passed in automatically.
Some say magic is bad
Pass your self explicitly!
Dieter
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[Zope-dev] Bug in ExternalMethods?
I think I've found a bug in ExternalMethod, but I don't know if it's
already been fixed or not.
Basically, the call signature of ExternalMethods seems to get mixed up
sometimes. I'm running Zope 2.5.1 on Linux.
Here's a small demonstration of the bug:
--test.py--
def test(self, a_string, an_int, a_named_arg=1):
"""bug provoking?"""
template = """a_string = %s; type(a_string) -> %s\n
an_int = %s; type(an_int) -> %s\n
a_named_arg = %s; type(a_named_arg) -> %s"""
return template % (a_string, type(a_string), an_int, type(an_int),
a_named_arg, type(a_named_arg))
--Script (Python)--
return container.test('tim', 10, a_named_arg=(1,1))
return container.test('tim', 10, (1,1))
You can see the dodgy behaviour by switching between the two test() calls
in the Script (Python).
tim
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