[Sqlalchemy-tickets] [sqlalchemy] #2943: @validates on inherited subclasses

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

#2943: @validates on inherited subclasses
--------------------+------------------------------------
 Reporter:  zzzeek  |           Owner:  zzzeek
     Type:  defect  |          Status:  new
 Priority:  high    |       Milestone:  0.9.3
Component:  orm     |        Severity:  major - 1-3 hours
 Keywords:          |  Progress State:  in queue
--------------------+------------------------------------
 {{{
 #!python
 from sqlalchemy import *
 from sqlalchemy.orm import *
 from sqlalchemy.ext.declarative import declarative_base

 Base = declarative_base()

 class A(Base):
     __tablename__ = 'a'

     id = Column(Integer, primary_key=True)
     data = Column(String)

     @validates('data')
     def validate(self, key, value):
         return "yup A " + value


 class B(A):
     @validates('data')
     def validate(self, key, value):
         return "yup B " + value

 for obj in (A(), B()):
     obj.data = "value"
     print(obj.data)

 }}}

 so here's a patch that makes the second one print "yup A yup B value",
 e.g. runs both validators:

 {{{
 #!diff
 diff --git a/lib/sqlalchemy/orm/strategies.py
 b/lib/sqlalchemy/orm/strategies.py
 index 2c18e81..fb8e0aa 100644
 --- a/lib/sqlalchemy/orm/strategies.py
 +++ b/lib/sqlalchemy/orm/strategies.py
 @@ -38,26 +38,21 @@ def _register_attribute(strategy, mapper, useobject,

      attribute_ext = list(util.to_list(prop.extension, default=[]))

 -    listen_hooks = []
 +    pre_validate_hooks = []
 +    post_validate_hooks = []

      if useobject and prop.single_parent:
 -        listen_hooks.append(single_parent_validator)
 +        pre_validate_hooks.append(single_parent_validator)

 -    if prop.key in prop.parent.validators:
 -        fn, opts = prop.parent.validators[prop.key]
 -        listen_hooks.append(
 -            lambda desc, prop: orm_util._validator_events(desc,
 -                                prop.key, fn, **opts)
 -            )

      if useobject:
 -        listen_hooks.append(unitofwork.track_cascade_events)
 +        post_validate_hooks.append(unitofwork.track_cascade_events)

      # need to assemble backref listeners
      # after the singleparentvalidator, mapper validator
      backref = kw.pop('backref', None)
      if backref:
 -        listen_hooks.append(
 +        post_validate_hooks.append(
              lambda desc, prop: attributes.backref_listeners(desc,
                                  backref,
                                  uselist)
 @@ -85,7 +80,15 @@ def _register_attribute(strategy, mapper, useobject,
                  **kw
                  )

 -            for hook in listen_hooks:
 +            for hook in pre_validate_hooks:
 +                hook(desc, prop)
 +
 +            for super_m in m.iterate_to_root():
 +                if prop.key in super_m.validators:
 +                    fn, opts = super_m.validators[prop.key]
 +                    orm_util._validator_events(desc, prop.key, fn,
 **opts)
 +
 +            for hook in post_validate_hooks:
                  hook(desc, prop)

  @properties.ColumnProperty.strategy_for(instrument=False, deferred=False)
 }}}

 but is that what we want?  or should B's validator replace A's?

 if the latter then we just do this:

 {{{
 #!python
             for super_m in m.iterate_to_root():
                 if prop.key in super_m.validators:
                     fn, opts = super_m.validators[prop.key]
                     orm_util._validator_events(desc, prop.key, fn, **opts)
                     break   # just the one
 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2943>
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