#9107: Nested class name mangling can be wrong in case of double nesting
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Reporter: hivert | Owner: nthiery
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: categories | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Simon King | Merged in:
Dependencies: #12808 | Stopgaps:
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Changes (by {'newvalue': u'Simon King', 'oldvalue': ''}):
* status: new => needs_review
* author: => Simon King
Comment:
I think the attached patch solves the problem. I get:
{{{
sage: class Bla(UniqueRepresentation):
....: class Bla1(UniqueRepresentation):
....: class Bla11:
....: pass
....: class Bla2:
....: class Bla21:
....: pass
....:
sage: Bla.Bla1.Bla11
<class __main__.Bla.Bla1.Bla11 at 0x46e7808>
}}}
The change is in `modify_for_nested_pickle`, which is called recursively.
The idea is that the function should have an extra argument `first_run`,
that is True by default. If the extra argument is False, then it is
assumed that it is not applied for the first time.
Here: Since Bla.Bla1 is an instance of `NestedClassMetaclass`,
`modify_for_nested_pickle` is called on `Bla.Bla1.Bla11`, resulting in
`Bla.Bla1.Bla11.__name__=='Bla1.Bla11'`. However, since Bla is an instance
of `NestedClassMetaclass` as well, the function is applied to `Bla.Bla1`
and thus recursively to `Bla.Bla1.Bla11` another time.
Now, without my patch, in the second run, `modify_for_nested_pickle` would
be confused by the fact that `Bla.Bla1.__dict__` lists `Bla.Bla1.Bla11`
under the name `Bla11`, but `Bla11.__name__=='Bla1.Bla11'`. With my patch,
`modify_for_nested_pickle` expects exactly that naming scheme, and is thus
changing `Bla.Bla1.Bla11.__name__` into `"Bla.Bla1.Bla11"`.
Much !BlaBla, but I think it works...
'''__Potential problems__'''
{{{
sage: module = sys.modules['__main__']
sage: getattr(module, 'Bla1.Bla11')
<class __main__.Bla.Bla1.Bla11 at 0x46e7808>
sage: getattr(module, 'Bla.Bla1.Bla11')
<class __main__.Bla.Bla1.Bla11 at 0x46e7808>
}}}
Hence, Bla.Bla1.Bla11 is listed in the module under two different names.
If you think it is bad, then one could probably modify the function when
first_run is false, such that the name given in the first run is erased
from the module.
Moreover, the reviewer will likely find a speed regression, when
excessively creating nested unique representations. But that's hardly
realistic...
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9107#comment:3>
Sage <http://www.sagemath.org>
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