Autoreload Enum Error

[alexmarder]

I'm getting a weird error when trying to use autoreload and Enums. I have an Enum class defined in a file as:

class MyEnum(Enum):
    A = 'A'
    B = 'B'

Using %autoreload 2, if I try to add C = 'C' to MyEnum, or remove an existing definition, I get the following error:

[autoreload of updates_type failed: Traceback (most recent call last):
  File "/home/amarder/anaconda3/lib/python3.5/site-packages/IPython/extensions/autoreload.py", line 247, in check
    superreload(m, reload, self.old_objects)
RecursionError: maximum recursion depth exceeded
]

Sometimes it is a different error:

[autoreload of updates_type failed: Traceback (most recent call last):
  File "/home/amarder/anaconda3/lib/python3.5/site-packages/IPython/extensions/autoreload.py", line 247, in check
    superreload(m, reload, self.old_objects)
AttributeError: __abstractmethods__
]

I'm running the code on Debian Linux, using Anaconda with python 3.5.

[takluyver]

autoreload is a bit black magic, so it's not a big surprise when it breaks.

I'd guess that the recursion error is because enum values have a reference back to their class (e.g. MyEnum.A.__objclass__, so there's an infinite chain of attributes that it's trying to replace: MyEnum.A.__objclass__.A.__objclass__.<etc>

[alexmarder]

If that's true, is there a way to mark a class as having been already reloaded so autoreload does not try again?

[takluyver]

Not at present. Actually, I now think my guess was wrong; MyEnum.A is not a type, so it should be updated like that. You can see the code updating a class object here:

ipython/IPython/extensions/autoreload.py

Line 276 in e834116

def update_class(old, new):

[Carreau]

seem like in update_class the two references old_obj and new_obj can be the same (I'm going to guess that's the point of enums, where instances are shared.
So continue if they are the same should be enough.

[Carreau]

also we should bump the number of stacks shown to something like 10-ish (or make it configurable) to be able to debug things like that better.