Support recursion in custom objects

[jonapich]

I have this scenario trying to inspect some items from the boto package:

class test(object):
    def __init__(self):
        self.loop = self

a = test()
b = a

print DeepDiff(a, b)

--- cut ---
  File "E:\Projects\Repos\Cookbook\cookbooks-v8\stack-monitor\files\default\deepdiff.py", line 244, in __diffdict
    self.__diffit(t1[item], t2[item], parent=parent_text % (parent, item_str))
  File "E:\Projects\Repos\Cookbook\cookbooks-v8\stack-monitor\files\default\deepdiff.py", line 325, in __diffit
    self.__diffdict(t1, t2, parent, attributes_mode=True)
  File "E:\Projects\Repos\Cookbook\cookbooks-v8\stack-monitor\files\default\deepdiff.py", line 244, in __diffdict
    self.__diffit(t1[item], t2[item], parent=parent_text % (parent, item_str))
  File "E:\Projects\Repos\Cookbook\cookbooks-v8\stack-monitor\files\default\deepdiff.py", line 321, in __diffit
    elif isinstance(t1, Iterable):
  File "C:\Apps\Python\lib\abc.py", line 141, in __instancecheck__
    subtype in cls._abc_negative_cache):
  File "C:\Apps\Python\lib\_weakrefset.py", line 75, in __contains__
    return wr in self.data
RuntimeError: maximum recursion depth exceeded in cmp

[seperman]

What are you exactly trying to inspect in boto? I don't remember a self.loop in boto.
The test class you have made has a loop to itself so DeepDiff gets stuck in that loop since it tries to get to the bottom depth of your object,

[jonapich]

I have seen this sort of design multiple times - i know pytest has it as well. Of course there's no explicit "loop", that's for the bug's purpose; the point is that Python supports such circular references but DeepDiff doesn't.

The boto class I'm trying to compare is the ElasticLoadBalancer attributes. The "Health Check" attribute has an access point attribute that also lists the health checks, and that's where the loop may exist.

Take for instance any hierarchical object; most of them will have a link to parent. If you enter parent, and re-enter the same child from parent, you can also create this "loop". It's a common idiom.

You might want to check how the json library handles this case when serializing custom objects. I know it has a switch to enable/disable recursion protection.

[seperman]

Great point. I'm adding loop detection.

[seperman]

I just added recursion detection and added some tests. Please let me know if you again run into issues with boto. DeepDiff v0.5.5

[jonapich]

Bingo :) Thank you so much!