[SQLObject] RelatedJoin bug

[Edmund L. <el...@in...>]

I've found a couple of bugs in RelatedJoin...

1. If you're going to explicitly define a class for the mapping table, 
you cannot use .createTable() to create tables on either side of the 
join. This is because the RelatedJoin declaration forces SQLObject to 
try to create the mapping (intermediate) table again, and this causes an 
exception.


2. When the mapping table table is used to map two or more many:many 
relationships, the presence of null values in the mapping table causes 
an exception. Example test case:

Schema
------
create table cat (
     id     serial,
     name   text
);

create table dog(
     id     serial,
     name   text
);

create table person(
     id     serial,
     name   text
);

create table owner_map(
     id         serial,
     person_id  integer,
     cat_id     integer,
     dog_id     integer
);


Classes
-------
class Dog(SQLObject):
     _columns = [
         StringCol("name")]
     _joins = [
         RelatedJoin("Person",
             intermediateTable = "owner_map",
             joinColumn = "dog_id",
             otherColumn = "person_id")]

class Cat(SQLObject):
     _columns = [
         StringCol("name")]
     _joins = [
         RelatedJoin("Person",
             intermediateTable = "owner_map",
             joinColumn = "cat_id",
             otherColumn = "person_id")]

class Person(SQLObject):
     _columns = [
         StringCol("name")]
     _joins = [
         RelatedJoin("Dog",
             intermediateTable = "owner_map",
             joinColumn = "person_id",
             otherColumn = "dog_id"),
         RelatedJoin("Cat",
             intermediateTable = "owner_map",
             joinColumn = "person_id",
             otherColumn = "cat_id")]

class OwnerMap(SQLObject):
     _columns = [
         IntCol("personId"),
         IntCol("dogId", foreignKey="Dog"),
         IntCol("catId", foreignKey="Cat")]


How to raise the exception:
 >>> d = Dog.new(name="Snoopy")
 >>> c = Cat.new(name="Garfield")
 >>> p = Person.new(name="John")
 >>> p.addDog(d)
 >>> p.dogs
[<Dog 2 name='Snoopy'>]
 >>> p.cats
[Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "/usr/lib/python2.2/site-packages/SQLObject/SQLObject.py", line 
925, in __repr__
     return '<%s %i %s>' \
AttributeError: 'Cat' object has no attribute 'id'
 >>>

What's happening (I think) is that the query that SQLObject uses to find 
the right row in the mapping table is assuming that either no row is 
found, or that if a row is found, then a not null value for cat_id will 
exist. So the null/None value for cat_id in owner_map causes an exception.

I'd fix it, but I don't understand SQLObject well enough to do so. Sorry...


...Edmund.