form.save() fails silently - how to debug?

[Derek]

I'd appreciate some help with the following problem, under Django 1.4

When running with the models, forms and view as described below, the data from the form is *not* saved into the model.

However, when using the test code (shown at the end) in a shell environment, the data *is* saved as expected.

How can I tell why the form data is not saved in the view?  It appears to "fail silently" (i.e. no errors reported) - but adding print statements into the code reveal that the correct data is available just before the .save() function.  Is there a preferred approach for debugging this type of situation?

Thanks

Derek

# models

class ClientFile(Model):

    id = AutoField(primary_key=True)

    description = CharField(unique=True, max_length=255)

    file = FileField(upload_to='client', storage=CLIENT_STORAGE)

class ClientData(Model):

    id = AutoField(primary_key=True)

    clientfile = ForeignKey(ClientFile)

    #http://code.google.com/p/django-geo/source/browse/trunk/fields.py?r=13#49

    data_set = DictionaryField(blank=True, null=True)

# forms

class ClientDataForm(ModelForm):

    class Meta:

        abstract = True

        model = ClientData

        widgets = {

            'data_set': HiddenInput(),

            'clientfile': HiddenInput()

        }

class ClientDataFormLayout(ClientDataForm):

    label = CharField(max_length=255)

    top_left = CharField(max_length=255)

    bottom_right = CharField(max_length=255)

    def __init__(self, *args, **kwargs):

        super(ClientDataForm, self).__init__(*args, **kwargs)

    class Meta(ClientDataForm.Meta):

        pass

    def clean(self):

        cleaned = self.cleaned_data

        # copy for alteration

        cleaned_data = copy.deepcopy(self.cleaned_data)

        del cleaned_data['data_set']

        del cleaned_data['clientfile']

        cleaned['data_set'] = cleaned_data

        return cleaned

# view

    client_dataform_layout = ClientDataFormLayout()

    client = get_object_or_404(ClientFile, pk=1)

    initial = {'clientfile': client}

    if request.method == 'POST':

        formset = client_dataform_layout(request.POST, instance=client)

        if formset.is_valid():

            results = formset.save(commit=False)

            form_data = formset.cleaned_data  #  test only

            formset.save()

    else:

        formset = client_dataform_layout(instance=client, initial=initial)

    return render_to_response("clients/client_data.html",

                              locals(),

                              RequestContext(request))

# test code

formset = ClientDataFormLayout(data {'clientfile': 1, 'data_set': '',

                                     'top_left': 'AA', 'bottom_right': 'ZZ',

                                     'label': 'foobar'})

print formset.is_valid()

results = formset.save(commit=False)

formset.save()

cd = ClientData.objects.get(clientfile__pk=1)

print cd.data_set

[Karl Sutt]

I think

results = formset.save(commit=False)
formset.save()

should be

results = formset.save(commit=False)
results.save() 

Tervitades/Regards

Karl Sutt

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[Derek]

Thank you for the suggestion, but unfortunately that too does not work. 

I really need to find a way to get at the source of the problem; I would think an error message should be generated but none shows up...

On Thursday, July 26, 2012 9:47:00 AM UTC+2, Karl Sutt wrote:

I think

results = formset.save(commit=False)
formset.save()

should be

results = formset.save(commit=False)
results.save() 

Tervitades/Regards

Karl Sutt

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[Jirka Vejrazka]

> Thank you for the suggestion, but unfortunately that too does not work.
>
> I really need to find a way to get at the source of the problem; I would
> think an error message should be generated but none shows up...

Are you doing some magic in model's save() by any chance?

Jirka

[Jirka Vejrazka]

Sorry, I should have read your code before answering.

I'm struggling to understand what you do in your clean() method. Are
you sure you're returning the right set of data?

Jirka

[Derek]

The clean() method basically stores the non-model field data in the model's dictionary field.  If this method was faulty, then it would also cause problems in the test code.  As I said, when I print the data to console it looks OK.  I am still trying to find how and where the save() method indicates errors...?

[Karen Tracey]

On Fri, Jul 27, 2012 at 3:25 AM, Derek <game...@gmail.com> wrote:

The clean() method basically stores the non-model field data in the model's dictionary field.  If this method was faulty, then it would also cause problems in the test code.  As I said, when I print the data to console it looks OK.  I am still trying to find how and where the save() method indicates errors...?

Model save() would indicate an error by raising an exception, see:

https://github.com/django/django/blob/master/django/db/models/base.py#L444

I would attack the problem you are seeing by tracing through what's actually happening using pdb.

Karen
--
http://tracey.org/kmt/

[Derek]

Thanks Karen

I am not quite sure what you mean by "Model save() would indicate an error" - I am making a call to the form.save(), which in turn, I assume, should result in the data being saved to the model (although nothing gets saved in my case)?  No error is being raised that I can see.  

I have not used pdb before; I will need to look into how that works and how might help me.

On Friday, 27 July 2012 14:00:37 UTC+2, Karen Tracey wrote:

[Dan Gentry]

I too am a little confused by the clean() method and the data_set field.  It seems that the data_set would contain a copy of the ID value for a change operation, and be None for an add.  What purpose does that serve?

Perhaps comment the clean() method just to see if the other fields can be saved.

Also, I concur with Karl's suggestion to use results.save()

Good luck!

[Derek]

Just to follow up...

I have tried using pdb - but stepping into the Django code goes through hundreds of lines of records and, to be honest, its not clear at all what I should be looking for or where I would expect to see errors...  If there is any guidance in this respect, I would be happy to hear it.

As per Dan's suggestion, I have also tried stripping out all the non-model fields from the form, along with all the "funny" clean code (I now just have a straightforward return of the cleaned data). Again, no success: the cleaned data looks OK (in the print statement) but it is simply not saved.

[Derek]

Finally (!) a  solution. 

Turns out the problem is in line 53 of the code I originally posted:
    formset = client_dataform_layout(request.POST, instance=client)
when I omit the ", instance=client" part, then all works as expected...

I do need to understand the reason why that was causing a "silent fail", but at least I can make progress now.

Thanks to all who made suggestions.