Can't add ManyToMany relations on a new Model

[ccazette]

... and probably HasMany relations neither looking at the code...

These lines (Core_Model line 353 - don't know why they have been added from the original Jelly) :

        // Set an empty value to NULL for deleting relationships
        if (($field instanceof Jelly_Field_HasMany OR $field instanceof Jelly_Field_ManyToMany) AND empty($value))
        {
            $value = NULL;
        }

Actually set a the manytomany field to NULL, so the field is reported as 'changed' with a NULL value. If you then try to add a new relation, then this line (942) in the _change() method will trigger an exception as it will run array_merge with a NULL parameter :

    if ($add)
    {
        $changes = array_unique(array_merge($current, $changes));
    }

[creatoro]

@ccazette: I'm not sure if I understand what did you do. Do you say first you've deleted the original relationships by setting the field to NULL, then you've added new relationships?

[ccazette]

@creatoro : Sorry if unclear, I realized some words are mistyped. I did nothing in particular. Just used add() on a ManyToMany field triggers an error if there are no relations beforehand. Say an article has many to many categories. If you load an article that has no categories yet and use add() to add some, it triggers an exception.

I explained why this error happens : line 353 in Core_Model sets the field value to NULL, so the status of the field is set to changed, so when running add(), you're merging an array with a NULL value.

Note that I am pretty sure this applies to Has Many relations too...

Let me know if still unclear...

[ccazette]

Also note that I've commented these lines in Core_Model, that fixed the error and hasn't done any harm so far...

//          if (($field instanceof Jelly_Field_HasMany OR $field instanceof Jelly_Field_ManyToMany) AND empty($value))
//          {
//              $value = NULL;
//          }

[ccazette]

Ok I went further in tracking this... Commenting the line above breaks the set() method behavior when trying to set an empty value in the relation : $model->set('relations', array());
Indeed, Has Many and Many To Many fields are not queried when the model is loaded so we have an empty array in $model->_original['relations'], even if there are some relations. When running the set() method, the $current_value is retrieved from _original (line 348) and compared with the $value we want to set. If they are the same, we don't set. So when setting model relations back to an empty array, the value is not set.
Definitely not easy to explain.
Anyway, I think I found the right way to fix this : in addition to commenting the lines in my above comment, we should add the following condition in the if statement just under it (line 361) :

// Ensure data is really changed
if ($value === $current_value
    AND ! ($field->supports(Jelly_Field::ADD_REMOVE) AND empty($value)))
{
        continue;
}

So we continue set() even if we have a has many or a many to many field and an empty value. That fixes everything for me.

[ccazette]

PS : I believe this bug is the same as #96, but this has to be confirmed

[vitch]

I've run into exactly the same problem. I implemented your suggested change on my fork (see vitch/kohana-jelly@c6a981f ) and it seems to work with no side effects. I'm not sure what the thinking behind the original code was so I don't know if this is the best fix or not but it works for me - thanks @ccazette!

To replicate the problem try this:

$model->set('field', '');
$model->add('field', 'other_model');

Where field is a ManyToMany and other_model is a model of the correct type to add to the field.

This might seem like weird code but is a distillation of my actual code. In my case the ->set('field', '') happens based on what a user has input in a form. My code then consults a third party API and based on that can add more items to the field before the model is saved.