[PEAK] Default value lost in binding.Obtain()

Alexey Smishlayev alexey at xtech2.lv
Sat Oct 31 15:02:20 EDT 2015

Sorry, I suppose I didn't see the big picture. Anyways, this one works 
as good. I can confirm that in my case (onSubprocessConnected = 
binding.Obtain("onSubprocessConnected", default=lambda connection: None) 
it didn't work before the patch (I define onSubprocessConnected in 
another class up the hierarchy tree).

Thank you for the help! I hope it goes well with the tests.

Best regards,

On 31/10/15 16:49, PJ Eby wrote:
> That's not a typo.  It's part of a strategy to work with multi-part
> names.  If the name is a path like 'foo/bar' and acquiring 'foo'
> fails, you should not end up with the 'bar' attribute of your default,
> which is what would happen with your version.  My version still has a
> bug, in that it doesn't work right with *single*-part names, because
> the for-loop doesn't execute in that case.  This code really needs
> proper tests, but there were apparently never any real tests for this
> functionality in the first place.  Most of PEAK's early code was
> developed before "test first" and "test-driven" were my standard
> practice.  :-(
> Anyway, here's a new version that should fix both issues.  I will have
> to see about adding some proper tests for this thing and back-testing
> to make sure they fail without the patch.
> On Sat, Oct 31, 2015 at 3:09 AM, Alexey Smishlayev <alexey at xtech2.lv> wrote:
>> It does except for a little typo, at line 60 of the patch it should read "ob
>> = acquireComponent(component, attr, default)", then it works good. Thank
>> you!
>> Best regards,
>> Alexey
>> On 30/10/15 20:59, PJ Eby wrote:
>>> Does this patch work for you?
>>> On Wed, Oct 28, 2015 at 8:45 AM, Alexey Smishlayev <alexey at xtech2.lv>
>>> wrote:
>>>> Hi!
>>>> How can I get an svn checkout to incorporate described changes and
>>>> propose
>>>> another patch? This is essential for our software and I'd like to see it
>>>> merged in upstream as soon as possible.
>>>> Best regards,
>>>> Alexey
>>>> On 30/09/15 01:53, PJ Eby wrote:
>>>>> Thanks for reporting the problem.  Unfortunately your patch will mask
>>>>> any other sort of name error, including one that happens indirectly as
>>>>> a side effect of the lookup.  I think the correct fix is going to be
>>>>> to change the nameNotFound() method of config.IConfigurationRoot to
>>>>> include a default (defaulting to NOT_GIVEN), and have
>>>>> acquireComponent() take a default and pass it along to nameNotFound().
>>>>> This would handle the case of a direct lookup failing by returning the
>>>>> default, but still raise an error for any other part of the process
>>>>> getting a naming error.
>>>>> On Tue, Sep 29, 2015 at 9:03 AM, Alexey Smishlayev <alexey at xtech2.lv>
>>>>> wrote:
>>>>>> Hello!
>>>>>> Today, fiddling with the binding.Obtain() I noticed that the default
>>>>>> value
>>>>>> gets lost.
>>>>>> In my application, I have a component tree and I want an attribute to
>>>>>> be
>>>>>> defined in any component in that tree, so I created binding:
>>>>>>>        callback = binding.Obtain("callbackFunction", default=lambda
>>>>>>> arg:
>>>>>>> None)
>>>>>> So, in case that no component defines a callbackFunction, the lambda
>>>>>> function would be used as a fallback.
>>>>>> Unfortunately, "default" option is ignored unless target name contains
>>>>>> slashes (e.g. "/callbackFunction", "./callBackFunction",
>>>>>> "../callbackFunction")
>>>>>> I went to the peak/binding/components.py trying to fix it and propose
>>>>>> the
>>>>>> attached patch.
>>>>>> The problem is that default value was not propagated to the
>>>>>> acquireComponent() call, so an exception occurred.
>>>>>> Best regards,
>>>>>> Alexey Smishlayev
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