[ZODB-Dev] Inconsistent use of ConflictError

[Tino Wildenhain]

*nod*

I like the idea to clean up these things.

(not dependant, but related are the many string exceptions
 in the zope core)

Regards
Tino

--On Donnerstag, 16. August 2001 13:48 -0500 "John D. Heintz" <jheintz@isogen.com> wrote:

> Hear, hear!!
>
> John
>
>
> On Thursday 16 August 2001 13:31, Greg Ward wrote:
>> This doesn't bother me much anymore now that we're not seeing
>> ConflictError in practice (thanks to Connection.sync()), but it still
>> bugs me that ZODB is inconsistent in how it uses ConflictError.
>>
>> In particular, ConflictError appears to be raised in no fewer than 6
>> different ways throughout the ZODB/ZEO code (ignoring trivial
>> differences like "raise ConflictError" vs. "raise
>> POSException.ConflictError"):
>>
>>   raise ConflictError, `oid`
>>
>>   raise ConflictError(`oid`, `object.__class__`)
>>
>>   raise ConflictError, "transaction already invalidated"
>>
>>   raise POSException.ConflictError
>>
>>   raise POSException.ConflictError, (serial, oserial)
>>
>>   raise POSException.ConflictError(
>>                         'serial number mismatch (was: %s, has: %s)' %
>>                         (utils.U64(oserial), utils.U64(serial)))
>>
>> Do a recursive grep for "raise.*ConflictError" in StandaloneZODB to see
>> for yourself.
>>
>> This inconsistency makes it pretty much impossible to do anything with
>> the exception value; from an API point of view, all of the above might
>> as well be a bare "raise ConflictError".
>>
>> Proposal:
>>   * give ConflictError an actual interface, ie. some attributes,
>>     a constructor with keyword arguments, and a __str__() to format
>>     the error meaningfully
>>   * fix all occurences of "raise ConflictError" to conform to
>>     the new interface
>>
>> Here's a strawman class definition:
>>
>>   class ConflictError(TransactionError):
>>       """
>>
>>       Instance attributes:
>>         oid : string
>>           the OID (8-byte packed string) of the object in conflict
>>         klass_name : string
>>           the fully-qualified name of that object's class
>>         message : string
>>           a human-readable explanation of the error
>>         serials : (???, ???)
>>           pair of mystery objects -- I have no idea what these are,
>>           I'm just including them because bsddb3Storage/*.py want
>>           to provide this info
>>
>>       """
>>
>>       def __init__(self, message=None,
>>                    oid=None, klass_name=None, serials=None):
>>           # message would default to something like
>>           # "database conflict error"
>>
>>       def __str__ (self):
>>           return self.message  # with some or all of oid, klass_name, and
>>                                # serials pasted on in a meaningful way
>>
>> Hmmm, the ConflictError docstring should mention that conflicts can
>> occur on read as well.
>>
>> Thoughts?
>>
>>         Greg
>
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>
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