Manytomany widget- M2M fields appear blank in export via Admin export

I have the following models and M2M relationships:

class Market(models.Model):
    marketname = models.CharField(max_length=500)
    market_id = models.CharField(max_length=100, blank=True)

    def __str__(self):
        return self.marketname

class TeamMember(models.Model):
    firstname = models.CharField(max_length=100, default= "First Name")
    lastname = models.CharField(max_length=100, default= "Last Name")
    email = models.EmailField(max_length=254)

    def __str__(self):
        return self.email

class EmailReport(models.Model):
    name = models.CharField(max_length=1000)
    recipients = models.ManyToManyField('team.TeamMember', related_name="teamrecipients")
    frequency = models.CharField(max_length=1000, blank= True)
    markets = models.ManyToManyField('opportunities.Market', blank=True)
    def __str__(self):
        return self.name

The following is my admin.py for the EmailReport registration.

class EmailReportResource(resources.ModelResource):
    recipients = fields.Field(widget=ManyToManyWidget(TeamMember, field="email"))
    markets = fields.Field(widget=ManyToManyWidget(Market, field='marketname'))
    class Meta:
        model = EmailReport
        fields = ['id', 'name', 'recipients', 'markets']

class EmailReportAdmin(ImportExportModelAdmin):
    resource_class = EmailReportResource

admin.site.register(EmailReport, EmailReportAdmin)

I am able to export- and all char fields export normally- however, my M2M fields all appear blank.

Can anyone please point out my mistake?

Thank you so much!

[jackkinsella]

Same issue.

Update: I solved with the following code (I believe by adding attribute to Field)

class EventResource(models.ModelResource):
    tags = fields.Field(attribute="tags", widget=widgets.ManyToManyWidget(Tag, field='name'))
   ...
   
   class Meta:
             fields = (... 'tags__name')

[n8thanael]

I hope this helps someone dealing with the issue of M2M Fields appearing blank via Admin. I found that when I passed ‘field’ kwarg in the in the ManyToManyWidget(field=‘code’) it would work properly on the export portion (render() method) - but ‘field’ was defaulting to None when on the import. IDK why that was, but this is how I solved it. I created a customM2M widget class from ManyToManyWidget that first helped me diagnose the problem, and then made a new kwarg called ‘m2mField’ that I could pass ‘code’ in a second time - that would both make the export and import function correctly.

models.py

class TaxonomyTerm(StatusModel):
    code = models.CharField(
        primary_key=True,
        )
        
class AcademicPage(StatusModel):
    title = models.CharField()
    faculty_department = models.ManyToManyField(
        TaxonomyTerm,
        )

admin.py

from .custom_widgets import CustomM2M

class academicPageResource(resources.ModelResource):
    faculty_department = fields.Field(
        column_name='faculty_department',
        attribute='faculty_department',
        # Custom M2M was required here, because for some reason field='code'
        # wasn't being passed through to the normal import 'clean()' method
        # within the ManyToManyWidget() class - it did work on export or
        # 'render()' but didn't work at all on 'clean()' - it would revert to
        # "pk" which is normally correct, but my model specifies the primary
        # key as 'code'
        widget=CustomM2M(model=TaxonomyTerm, field='code', m2mField='code')
    )
    class Meta:
        fields = ('id','title')
        exclude = ('body_a','body_b','slug')
        model = AcademicPage

class Admin_academicpages(ImportExportModelAdmin):
    resource_class = academicPageResource

custom_widgets.py

from import_export.widgets import ManyToManyWidget

# this custom widget was built because the kwarg 'field' wasn't carrying in
# the 'code' needed to properly build out the model.object.filter(), it would
# default to 'pk' which wasn't the default primary key for my objects
class CustomM2M(ManyToManyWidget):
    def __init__(self, model, separator=None, field=None, *args, **kwargs):
        print(args)
        print(kwargs)
        if separator is None:
            separator = ','
        # IDKW, but field always comes in as None, even when set in admin.py
        if field is None:
            field = 'pk'
        self.model = model
        self.separator = separator
        self.field = field
        # added a new field that can carry the proper column name 'code' over
        self.m2mField = kwargs.get('m2mField', None)
        super(CustomM2M, self).__init__(model)

    # clean is the 'import' method that prepares the data received in a way
    # that will return well-formed django db - model.objects via filter()
    def clean(self, value, row=None, *args, **kwargs):
        if not value:
            return self.model.objects.none()
        if isinstance(value, (float, int)):
            ids = [int(value)]
        else:
            ids = value.split(self.separator)
            ids = filter(None, [i.strip() for i in ids])


        if self.m2mField is not None:
            id_field = '%s__in' % self.m2mField
            return self.model.objects.filter(**{id_field:ids})
        else 
            return self.model.objects.filter(**{
                '%s__in' % self.field: ids