Add a get_child_inlines() hook to inline admin classes

Co-authored-by: Jesús Leganés-Combarro 'piranna <piranna@gmail.com>
Co-authored-by: Brian Kohan <bckohan@gmail.com>

.gitignore

@@ -221,3 +221,4 @@ __marimo__/
 
 test1.db
 test2.db
+example/example.db

AUTHORS.md

@@ -36,6 +36,7 @@
 * Jacob Rief
 * James Murty
 * Jedediah Smith (proxy models support)
+* Jesús Leganés-Combarro (Auto-discover child models and inlines, #582)
 * John Furr
 * Jonas Haag
 * Jonas Obrist

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 v4.3.0 (202X-XX-XX)
 -------------------
 
+* Implemented `Include get_child_inlines() hook in stacked inline admin forms. <https://github.com/jazzband/django-polymorphic/pull/681>`_
 * Fixed `"multi-database support in inheritance accessors. <https://github.com/jazzband/django-polymorphic/pull/550>`_
 * Fixed `Caching in inheritance accessor functions <https://github.com/jazzband/django-polymorphic/pull/510>`_
 * Fixed `Foreign key resolves to parent class when using abstract models <https://github.com/jazzband/django-polymorphic/issues/437>`_

justfile

@@ -15,7 +15,7 @@ manage *COMMAND:
     import sys
     from django.core import management
     sys.path.append(os.getcwd())
-    os.environ["DJANGO_SETTINGS_MODULE"] = "polymorphic.tests.settings"
+    os.environ["DJANGO_SETTINGS_MODULE"] = "polymorphic.tests.debug"
     os.environ["SQLITE_DATABASES"] = "test1.db,test2.db"
     management.execute_from_command_line(sys.argv + "{{ COMMAND }}".split(" "))
 

src/polymorphic/admin/inlines.py

@@ -77,12 +77,22 @@ class PolymorphicInlineModelAdmin(InlineModelAdmin):
         for child_inline in self.child_inline_instances:
             self._child_inlines_lookup[child_inline.model] = child_inline
 
+    def get_child_inlines(self):
+        """
+        Return the derived inline classes which this admin should handle.
+
+        This should return an iterable of
+        :class:`~polymorphic.admin.inlines.PolymorphicInlineModelAdmin.Child classes,
+        to override :attr:`child_inlines.
+        """
+        return self.child_inlines or []
+
     def get_child_inline_instances(self):
         """
         :rtype List[PolymorphicInlineModelAdmin.Child]
         """
         instances = []
-        for ChildInlineType in self.child_inlines:
+        for ChildInlineType in self.get_child_inlines():
             instances.append(ChildInlineType(parent_inline=self))
         return instances
 

src/polymorphic/tests/admin.py

@@ -1,3 +1,4 @@
+from inspect import isclass
 from django.contrib.admin import register, ModelAdmin, site as admin_site
 from polymorphic.admin import (
     StackedPolymorphicInline,
@@ -35,20 +36,25 @@ class PlainAAdmin(ModelAdmin):
     search_fields = ["field1"]
 
 
-class InlineModelAChild(StackedPolymorphicInline.Child):
-    model = InlineModelA
-
-
-class InlineModelBChild(StackedPolymorphicInline.Child):
-    model = InlineModelB
-    autocomplete_fields = ["plain_a"]
-
-
 class Inline(StackedPolymorphicInline):
     model = InlineModelA
-    child_inlines = (InlineModelAChild, InlineModelBChild)
+
+    def get_child_inlines(self):
+        return [
+            child
+            for child in self.__class__.__dict__.values()
+            if isclass(child) and issubclass(child, StackedPolymorphicInline.Child)
+        ]
+
+    class InlineModelAChild(StackedPolymorphicInline.Child):
+        model = InlineModelA
+
+    class InlineModelBChild(StackedPolymorphicInline.Child):
+        model = InlineModelB
+        autocomplete_fields = ["plain_a"]
 
 
 @register(InlineParent)
 class InlineParentAdmin(PolymorphicInlineSupportMixin, ModelAdmin):
     inlines = (Inline,)
+    extra = 1

src/polymorphic/tests/debug.py

@@ -0,0 +1,3 @@
+from .settings import *
+
+DEBUG = True

src/polymorphic/tests/settings.py

@@ -101,6 +101,7 @@ INSTALLED_APPS = (
     "polymorphic",
     "polymorphic.tests",
 )
+
 MIDDLEWARE = (
     "django.middleware.common.CommonMiddleware",
     "django.contrib.sessions.middleware.SessionMiddleware",

src/polymorphic/tests/test_admin.py

@@ -93,6 +93,15 @@ class PolymorphicAdminTests(AdminTestCase):
         self.admin_post_delete(Model2A, d_obj.pk)
         pytest.raises(Model2A.DoesNotExist, (lambda: d_obj.refresh_from_db()))
 
+    def test_get_child_inlines(self):
+        from .admin import Inline
+
+        inline = Inline(parent_model=InlineParent, admin_site=admin.site)
+        child_inlines = inline.get_child_inlines()
+        self.assertEqual(len(child_inlines), 2)
+        self.assertEqual(child_inlines[0], Inline.InlineModelAChild)
+        self.assertEqual(child_inlines[1], Inline.InlineModelBChild)
+
     def test_admin_inlines(self):
         """
         Test the registration of inline models.
@@ -205,9 +214,6 @@ class _GenericAdminFormTest(StaticLiveServerTestCase):
 
     def setUp(self):
         """Create an admin user before running tests."""
-        self.admin_username = "admin"
-        self.admin_password = "password"
-
         self.page = self.browser.new_page()
         # Log in to the Django admin
         self.page.goto(f"{self.live_server_url}/admin/login/")