Dynamic subscription

newsletter/admin.py

@@ -86,7 +86,9 @@ def admin_messages(self, obj):
     admin_messages.short_description = ''
 
     def admin_subscriptions(self, obj):
-        return self._admin_url(obj, Subscription, _("Subscriptions"))
+        link_text = _("Subscriptions") if not obj.subscription_generator_class \
+            else obj.subscription_generator_class.rsplit('.', 1)[-1]
+        return self._admin_url(obj, Subscription, link_text)
     admin_subscriptions.short_description = ''
 
     def admin_submissions(self, obj):

newsletter/migrations/0009_newsletter_subscription_generator_class.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.1.7 on 2021-03-27 03:29
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('newsletter', '0008_longer_subscription_name'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='newsletter',
+            name='subscription_generator_class',
+            field=models.CharField(blank=True, max_length=200, null=True),
+        ),
+    ]

newsletter/models.py

@@ -1,7 +1,9 @@
 import logging
 import os
 import time
+import importlib
 from datetime import datetime
+from abc import abstractmethod
 
 import django
 
@@ -44,6 +46,8 @@ class Newsletter(models.Model):
         max_length=200, verbose_name=_('sender'), help_text=_('Sender name')
     )
 
+    subscription_generator_class = models.CharField(max_length=200, blank=True, null=True)
+
     visible = models.BooleanField(
         default=True, verbose_name=_('visible'), db_index=True
     )
@@ -97,6 +101,17 @@ def get_templates(self, action):
 
         return subject_template, text_template, html_template
 
+    def get_subscription_generator(self):
+        if self.subscription_generator_class:
+            if "." not in self.subscription_generator_class:
+                raise ModuleNotFoundError("missing module for subscription generator class")
+            module_name, class_name = self.subscription_generator_class.rsplit(".", 1)
+            module = importlib.import_module(module_name)
+            self.subscription_generator = getattr(module, class_name)()
+            return self.subscription_generator
+        else:
+            return None
+
     def __str__(self):
         return self.title
 
@@ -135,6 +150,14 @@ def get_default(cls):
             return None
 
 
+def newsletter_presave(sender, instance, **kwargs):
+    if instance.subscription_generator_class:
+        instance.get_subscription_generator()
+
+
+models.signals.pre_save.connect(newsletter_presave, Newsletter)
+
+
 class Subscription(models.Model):
     user = models.ForeignKey(
         AUTH_USER_MODEL, blank=True, null=True, verbose_name=_('user'),
@@ -547,6 +570,21 @@ def get_default(cls):
             return None
 
 
+class SubscriptionGenerator:
+    """
+    Interface for subscription generators.
+    Users must implement the generate_subscriptions method.
+    """
+    @abstractmethod
+    def generate_subscriptions(self, submission):
+        """
+        :param submission: the submission for which we are generating the subscription list
+        :return: the list of Subscription objects.
+        They may just be in memory Subscription objects, no need to save them to the DB.
+        """
+        raise NotImplementedError()
+
+
 class Submission(models.Model):
     """
     Submission represents a particular Message as it is being submitted
@@ -574,11 +612,19 @@ def extra_headers(self):
         }
 
     def submit(self):
-        subscriptions = self.subscriptions.filter(subscribed=True)
+        subscriptions = list(self.subscriptions.filter(subscribed=True).all())
+
+        if self.newsletter.subscription_generator_class:
+            logger.info("Dynamically generating subscriptions")
+            subscribed_emails = {s.email for s in subscriptions}
+            unsubscribed_emails = {s.email for s in self.newsletter.subscription_set.filter(unsubscribed=True).all()}
+            dynamic_subscriptions = self.newsletter.get_subscription_generator().generate_subscriptions(self)
+            subscriptions += (s for s in dynamic_subscriptions
+                              if s.email not in subscribed_emails and s.email not in unsubscribed_emails)
 
         logger.info(
             gettext("Submitting %(submission)s to %(count)d people"),
-            {'submission': self, 'count': subscriptions.count()}
+            {'submission': self, 'count': len(subscriptions)}
         )
 
         assert self.publish_date < now(), \

tests/test_mailing.py

@@ -11,7 +11,7 @@
 from django.utils.timezone import now
 
 from newsletter.models import (
-    Newsletter, Subscription, Submission, Message, Article, get_default_sites, Attachment
+    Newsletter, Subscription, Submission, Message, Article, get_default_sites, Attachment, SubscriptionGenerator
 )
 from newsletter.utils import ACTIONS
 
@@ -172,6 +172,57 @@ def test_submission_unsubscribed_unactivated(self):
         self.assertEqual(list(subscriptions), [self.s2])
 
 
+class TestingSubscriptionGenerator(SubscriptionGenerator):
+    def generate_subscriptions(self, submission):
+        return [
+            Subscription(newsletter=submission.newsletter, name_field='name 2', email_field='[email protected]'),
+            Subscription(newsletter=submission.newsletter, name_field='name 3', email_field='[email protected]'),
+            Subscription(newsletter=submission.newsletter, name_field='name 4', email_field='[email protected]'),
+        ]
+
+
+class SubscriptionGeneratorTestCase(MailingTestCase):
+    def setUp(self):
+        super().setUp()
+        self.n.subscription_generator_class = 'tests.test_mailing.TestingSubscriptionGenerator'
+        self.n.save()
+        self.sub = Submission.from_message(self.m)
+        self.sub.save()
+
+    def test_subscription_generator(self):
+        """ Test the dynamic generation of subscriptors """
+        # Manually add some subscriptions, including an unsubscription
+        Subscription.objects.filter(newsletter=self.n).delete()
+        sub1 = Subscription.objects.create(name='name 1', email='[email protected]', newsletter=self.n, subscribed=True)
+        sub2 = Subscription.objects.create(name='name 2', email='[email protected]', newsletter=self.n, subscribed=True)
+        sub3 = Subscription.objects.create(name='name 3', email='[email protected]', newsletter=self.n, unsubscribed=True)
+        self.sub.subscriptions.add(sub1)
+        self.sub.subscriptions.add(sub2)
+        self.sub.subscriptions.add(sub3)
+
+        self.sub.submit()
+        Submission.submit_queue()
+        submission = Submission.objects.get(pk=self.sub.pk)
+        self.assertTrue(submission.sent)
+        self.assertEqual(len(mail.outbox), 3)
+
+    def test_nonexistent_generator_class(self):
+        """ Test failure when generator class does not exist """
+        try:
+            self.n.subscription_generator_class = 'nonexistent_module.SomeClass'
+            self.n.save()
+            self.fail('Should not reach this')
+        except ModuleNotFoundError:
+            pass
+
+        try:
+            self.n.subscription_generator_class = 'newsletter.models.NonexistentClass'
+            self.n.save()
+            self.fail('Should not reach this')
+        except AttributeError:
+            pass
+
+
 class SubmitSubmissionTestCase(MailingTestCase):
     def setUp(self):
         super().setUp()