Records with notnull foreign keys currently return false for isValid() when an unpersisted relation is set.

See attached test for examples.

Suggested (imperfect) fix:

I made the following change in Doctrine_Table::validateField(). Change:

if ($value === self::$_null) {
    $value = null;
} else if ($value instanceof Doctrine_Record) {
    $value = $value->getIncremented();
}

To:

if ($value === self::$_null) {
    $value = null;
} else if ($value instanceof Doctrine_Record && $value->exists()) {
    $value = $value->getIncremented();
} else if ($value instanceof Doctrine_Record) {
    foreach($this->getRelations() as $relation) {
        if($fieldName == $relation->getLocalFieldName() && get_class($value) == $relation->getClass()) {
            return $errorStack;
        }
    }
}

Basically, if $value is a Doctrine_Record object, only grab the primary key if it exists. Otherwise, just make sure it's the right class. I realize this is far from perfect, but I think it's preferable to the current behavior.