Remove and prevent inaccurate __eq__ implementations on datatype #6061
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
stuhood
changed the title
…y struct equality.
cosmicexplorer
approved these changes
Jul 3, 2018
| @@ -89,6 +94,9 @@ def __eq__(self, other): | |||
| return False | |||
| # Explicitly return super.__eq__'s value in case super returns NotImplemented | |||
| return super(DataType, self).__eq__(other) | |||
| # We define an attribute on the `cls` level definition of `__eq__` that will allow us to detect | |||
| # that it has been overridden. | |||
| __eq__._eq_override_canary = None | |||
There was a problem hiding this comment.
This is why I love dynamic languages!!!
|
Integration test failed on something that is clearly a network error... merging. |
illicitonion
reviewed
Jul 3, 2018
| @@ -60,6 +60,11 @@ def make_type_error(cls, msg, *args, **kwargs): | |||
| return TypeCheckError(cls.__name__, msg, *args, **kwargs) | |||
|
|
|||
| def __new__(cls, *args, **kwargs): | |||
| # TODO: Ideally we could execute this exactly once per `cls` but it should be a | |||
There was a problem hiding this comment.
Can't we just do this in the datatype constructor, changing return type(superclass_name, (DataType,), {}) to:
t = type(superclass_name, (DataType,), {})
if not hasattr(t.__eq__, '_eq_override_canary'):
raise ...
return t
?
There was a problem hiding this comment.
That would check super classes, but not subclasses, I think?
There was a problem hiding this comment.
Aah, we subclass these things? Got it :)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Problem
Overriding
__eq__ondatatypeviolates structural equality, and the assumptions that people have aboutdatatypeinstances. Moreover, it is very error prone in the presence of #6059, which will be using__eq__to determine whether objects have changed.Solution
Make it impossible to override
__eq__accidentally ondatatypeby attaching a canary to the__eq__method definition on the generated class. Remove a few__eq__implementations that violated structural equality and were thus causing issues in #6059.Result
datatypesbehave as expected more frequently, and bugs are avoided. There is no noticeable impact on performance in my testing (likely these were overridden back when every object ended up memoized, rather than justKeyinstances).