[Sqlalchemy-tickets] [sqlalchemy] #2744: Custom TypeDecorator can no longer convert boolean type to another type

[sqlalchemy <mi...@zz...>]

#2744: Custom TypeDecorator can no longer convert boolean type to another type
-------------------------+---------------------------------------
 Reporter:  vladimir-lu  |           Owner:  zzzeek
     Type:  defect       |          Status:  new
 Priority:  medium       |       Milestone:  0.8.xx
Component:  sql          |        Severity:  minor - half an hour
 Keywords:               |  Progress State:  awaiting triage
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 This is a 0.8.0 -> 0.8.1 regression. Basically, I have a custom type
 decorator like the following:

 {{{
 class BitIndicatorType(types.TypeDecorator):
     """
     Converts '0' and '1' bits to True/False values and vica-versa
     """

     impl = types.SmallInteger

     def process_bind_param(self, value, dialect):
         return 1 if value else 0

     def process_result_value(self, value, dialect):
         return True if value == 1 else False

     def copy(self):
         return BitIndicatorType()
 }}}

 This type in turn is used in ORM mapped objects and in queries - so for
 example if we have enabledInd = Column('enabled_ind', BitIndicatorType)
 and obj.enabledInd == True then I expect the SQL to be: {{{... where
 enabled_ind = 1...}}}

 However, due to
 https://github.com/zzzeek/sqlalchemy/commit/5884c2e7e5b46cee29b90aa3f7161e7380e3e2a5
 the explicit boolean check added in expression.py _const_expr, the true
 gets passed to the dialect directly before being passed through the type
 decorator.

 The expected behaviour is that the type decorator be checked even when the
 value is a boolean value.

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2744>
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