'optgroups' error displaying ManyToMany field as checkboxes

[yellowlabrat]

First time poster, so let me know if this is not the appropriate place for this. :) I've posted on Django Forum and was directed to file an issue here.

I’m attempting to display records from a Many-to-Many field relationship in a ModelForm.

When I load my page/template in the browser, I see the following error:

File "...path here.../lib/python3.9/site-packages/django/template/base.py", line 569, in find_filter
    raise TemplateSyntaxError("Invalid filter: '%s'" % filter_name)
django.template.exceptions.TemplateSyntaxError: Invalid filter: 'optgroups'

treatment_goal field in models.py
treatment_goal = models.ManyToManyField(MyObjective)

MyObjective in models.py (obviously pared down for simplicity)

class MyObjective(TheBaseClass):
    client = models.ForeignKey(Client, on_delete=models.CASCADE)
    objective = models.CharField(max_length=300, default='')

    def __str__(self):
        return str(self.objective)

form in forms.py

class MyForm(ModelForm):
	class Meta:
		model = MyModel
		widgets = {
			'treatment_goal': widgets.CheckboxSelectMultiple
		}

	def __init__(self, *args, **kwargs):
		super().__init__(*args, **kwargs)
		self.helper = FormHelper()
		self.helper.layout = Layout(
			Fieldset('',
				'treatment_goal',
                        )
                )

If I don’t use the widgets.CheckboxSelectMultiple code, it renders the field as a Multi-Select field and works fine. But the moment I add the CheckboxSelectMultiple code, it gives the error.

The widgets.CheckboxSelectMultiple code is working fine in another location on forms.py for a field that looks like this in models.py:
communication_prefs = MultiSelectField(choices=CommunicationPref.choices, blank=True, default='')

If it helps, CommunicationPref.choices looks like this in models.py:

class CommunicationPref(models.TextChoices):
    PHONE = 'Phone', _('Phone')
    TEXT = 'Text', _('Text')
    EMAIL = 'Email', _('Email')

Again, that is an example of where it is working.

Ultimately, I think the error is indicating that the template being used by crispy-bootstrap5 (radio_checkbox_select.html) does not like the values that are coming back from the ManyToMany field, possibly? The values coming back from the ManyToMany field are a short sentences (strings) as shown in MyObjective code above.

This is the radio_checkbox_select.html file being called:
https://github.com/django-crispy-forms/crispy-bootstrap5/blob/main/crispy_bootstrap5/templates/bootstrap5/layout/radio_checkbox_select.html

Hope that helps explain the issue!

[smithdc1]

The widgets.CheckboxSelectMultiple code is working fine in another location on forms.py for a field that looks like this in models.py:
communication_prefs = MultiSelectField(choices=CommunicationPref.choices, blank=True, default='')

It seems to me that this MultiSelectField is the issue. As far as I'm aware this isn't a widget that comes with Django. I'm afraid that crispy-forms can't support custom widget (be it in 3rd party packages or from code in user-land).

A custom template for this field would be my recommendation here.

	def __init__(self, *args, **kwargs):
		super().__init__(*args, **kwargs)
		self.helper = FormHelper()
		self.helper.layout = Layout(
			Fieldset('',
				Field('treatment_goal', template="....") # Use Field and provide template name. 
                        )
                )

[yellowlabrat]

Ah, you are so correct and I didn't think of that back when I posted this! I was so deep into the new project I had forgotten that the MultiSelectField was not official Django.
It comes from this package: https://pypi.org/project/django-multiselectfield/
Thank you for the solution and that makes total sense.