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Make class Message unhashable #262

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Make class Message unhashable #262

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87f96a6
Add __hash__ to class Message to make it hashable in Python 3
ttanay Mar 3, 2019
0ace821
Make __hash__ implementation consistent with __eq__
ttanay Mar 11, 2019
ea930a3
Make __hash__ None for class Message
ttanay Mar 11, 2019
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4 changes: 4 additions & 0 deletions apitools/base/protorpclite/messages.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1058,6 +1058,10 @@ def __ne__(self, other):
"""
return not self.__eq__(other)

def __hash__(self):
"""Hash by __tags"""
return hash(self.__tags)
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Looking closer at this, self.__tags is a dictionary, which is unhashable. Looks like we have two options:

  • Keep the class unhashable.
  • Hash over contents of __tags or it's subset, if we can consider Message objects immutable, which we probably cannot.

Is there a reason to believe Message objects are immutable? If not, I think making them unhashable makes most sense.

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self.__tags is a dict! I missed that, sorry 🤦‍♂️

I think Message should be mutable. Therefore, it should be unhashable.
This class is hashable in Python 2. Making it unhashable would break compatibility in Python 3. But, that is also an option.

If we make it unhashable, we should add __hash__ = None to the class to keep the behaviour consistent in Python 2 as well.
OR
If we want to keep behaviour consistent in Python 3, while not breaking compatibility, we should add __hash__ = object.__hash__ to the class.

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There are good reasons why in Python 3 __hash__ is not implemented by default, in this light, I think the better way to keep compatibility would be to set __hash__ = None. This may require cascading changes for Py2 users of apitools. But same/similar changes would still be needed in downstream codebase to make relevant code Python3-compatible, so that may encourage users of apitools to fix their code sooner than later.

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@ttanay ttanay Mar 11, 2019 •
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I agree! I'll make that change :)



class FieldList(list):
"""List implementation that validates field values.
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