Added list_signals command.

Author: emorozov

django_extensions/management/commands/list_signals.py

@@ -0,0 +1,71 @@
+# -*- coding: utf-8 -*-
+# Based on https://gist.github.com/voldmar/1264102
+# and https://gist.github.com/runekaagaard/2eecf0a8367959dc634b7866694daf2c
+
+import gc
+import inspect
+import ctypes
+import weakref
+from collections import defaultdict
+
+from django.core.management.base import BaseCommand
+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
+)
+from django.utils.encoding import force_str
+
+
+MSG = '{module}.{name} #{line}'
+
+SIGNAL_NAMES = {
+    pre_init: 'pre_init',
+    post_init: 'post_init',
+    pre_save: 'pre_save',
+    post_save: 'post_save',
+    pre_delete: 'pre_delete',
+    post_delete: 'post_delete',
+    m2m_changed: 'm2m_changed',
+    pre_migrate: 'pre_migrate',
+    post_migrate: 'post_migrate',
+}
+
+
+class Command(BaseCommand):
+    help = 'List all signals by model and signal type'
+
+    def handle(self, *args, **options):
+        signals = [obj for obj in gc.get_objects() if isinstance(obj, ModelSignal)]
+        models = defaultdict(lambda: defaultdict(list))
+
+        for signal in signals:
+            signal_name = SIGNAL_NAMES.get(signal, 'unknown')
+            for receiver in signal.receivers:
+                lookup, receiver = receiver
+                if isinstance(receiver, weakref.ReferenceType):
+                    receiver = receiver()
+                if receiver is None:
+                    continue
+                receiver_id, sender_id = lookup
+
+                model = ctypes.cast(sender_id, ctypes.py_object).value
+                if model:
+                    models[model][signal_name].append(MSG.format(
+                        name=receiver.__name__,
+                        module=receiver.__module__,
+                        line=inspect.getsourcelines(receiver)[1],
+                        path=inspect.getsourcefile(receiver))
+                    )
+
+        output = []
+        for key in sorted(models.keys(), key=str):
+            verbose_name = force_str(key._meta.verbose_name)
+            output.append('{}.{} ({})'.format(
+                key.__module__, key.__name__, verbose_name))
+            for signal_name in sorted(models[key].keys()):
+                lines = models[key][signal_name]
+                output.append('    {}'.format(signal_name))
+                for line in lines:
+                    output.append('        {}'.format(line))
+
+        return '\n'.join(output)

docs/list_signals.rst

@@ -0,0 +1,15 @@
+list_signals
+============
+
+:synopsis: Lists all signals defined in the project grouped by model and
+           signal type
+
+
+Example Usage
+-------------
+
+With *django-extensions* installed you can review all defined handlers using
+*list_signals* command::
+
+  # As above but non-interactive
+  $ ./manage.py list_signals

tests/management/commands/test_list_signals.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+import re
+from io import StringIO
+
+from django.test import TestCase
+from django.core.management import call_command
+
+
+class ListSignalsTests(TestCase):
+    """Tests for list_signals command."""
+
+    def setUp(self):
+        self.out = StringIO()
+
+    def test_should_print_all_signals(self):
+        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.HasOwnerModel (has owner model)
+    pre_save
+        tests.testapp.models.dummy_handler #
+'''
+
+        call_command('list_signals', stdout=self.out)
+
+        # Strip line numbers to make the test less brittle
+        out = re.sub(r'(?<=#)\d+', '', self.out.getvalue(), re.M)
+        self.assertIn(expected_result, out)

tests/testapp/models.py

@@ -3,6 +3,7 @@
 
 from django.db import models
 from django.contrib.auth import get_user_model
+from django.db.models.signals import pre_save
 
 from django_extensions.db.fields import AutoSlugField, ModificationDateTimeField, RandomCharField, ShortUUIDField
 from django_extensions.db.fields.json import JSONField
@@ -492,3 +493,10 @@ def has_defaults(self, one=1, two='Two', true=True, false=False, none=None):
 
     class Meta:
         app_label = 'django_extensions'
+
+
+def dummy_handler(sender, instance, **kwargs):
+    pass
+
+
+pre_save.connect(dummy_handler, sender=HasOwnerModel)