From 8f3007a5893ca933773aa11c2acd52db61068aac Mon Sep 17 00:00:00 2001
From: Eugene Morozov <jmv@emorozov.net>
Date: Fri, 13 Jan 2023 14:55:13 +0200
Subject: [PATCH] Fixes exception when there are signals connected to abstract
 models.

---
 .../management/commands/list_signals.py       | 21 ++++++++++++++++---
 .../management/commands/test_list_signals.py  | 17 ++++++++++++---
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/django_extensions/management/commands/list_signals.py b/django_extensions/management/commands/list_signals.py
index c41aa6f14..ba6193b79 100644
--- a/django_extensions/management/commands/list_signals.py
+++ b/django_extensions/management/commands/list_signals.py
@@ -7,8 +7,8 @@
 import weakref
 from collections import defaultdict
 
-from django.apps import apps
 from django.core.management.base import BaseCommand
+from django.db.models import Model
 from django.db.models.signals import (
     ModelSignal, pre_init, post_init, pre_save, post_save, pre_delete,
     post_delete, m2m_changed, pre_migrate, post_migrate
@@ -31,12 +31,27 @@
 }
 
 
+def get_all_models() -> set[Model]:
+    """
+    Returns set of all models defined in all apps.
+
+    This implementation is required because apps.get_models() is an internal API and
+    doesn't return abstract models.
+    """
+    result = set()
+    generation = {Model}
+    while generation:
+        generation = {sc for c in generation for sc in c.__subclasses__()}
+        result.update(generation)
+
+    return result
+
+
 class Command(BaseCommand):
     help = 'List all signals by model and signal type'
 
     def handle(self, *args, **options):
-        all_models = apps.get_models(include_auto_created=True, include_swapped=True)
-        model_lookup = {id(m): m for m in all_models}
+        model_lookup = {id(m): m for m in get_all_models()}
 
         signals = [obj for obj in gc.get_objects() if isinstance(obj, ModelSignal)]
         models = defaultdict(lambda: defaultdict(list))
diff --git a/tests/management/commands/test_list_signals.py b/tests/management/commands/test_list_signals.py
index 82ac9c4cd..a616855a4 100644
--- a/tests/management/commands/test_list_signals.py
+++ b/tests/management/commands/test_list_signals.py
@@ -1,10 +1,16 @@
-# -*- coding: utf-8 -*-
 import re
 from io import StringIO
 
+from django.db.models.signals import post_delete
 from django.test import TestCase
 from django.core.management import call_command
 
+from tests.testapp.models import AbstractInheritanceTestModelParent
+
+
+def delete_dummy_handler(sender, instance, **kwargs):
+    pass
+
 
 class ListSignalsTests(TestCase):
     """Tests for list_signals command."""
@@ -12,16 +18,21 @@ class ListSignalsTests(TestCase):
     def setUp(self):
         self.out = StringIO()
 
+        post_delete.connect(delete_dummy_handler, sender=AbstractInheritanceTestModelParent)
+
     def test_should_print_all_signals(self):
-        expected_result = '''django.contrib.sites.models.Site (site)
+        expected_result = """django.contrib.sites.models.Site (site)
     pre_delete
         django.contrib.sites.models.clear_site_cache #
     pre_save
         django.contrib.sites.models.clear_site_cache #
+tests.testapp.models.AbstractInheritanceTestModelParent (abstract inheritance test model parent)
+    post_delete
+        tests.management.commands.test_list_signals.delete_dummy_handler #
 tests.testapp.models.HasOwnerModel (has owner model)
     pre_save
         tests.testapp.models.dummy_handler #
-'''
+"""
 
         call_command('list_signals', stdout=self.out)