Fixed #27755 -- Added ModelAdmin.get_inlines() hook.

django/contrib/admin/options.py

@@ -327,6 +327,10 @@ class BaseModelAdmin(metaclass=forms.MediaDefiningClass):
             return self.fieldsets
         return [(None, {'fields': self.get_fields(request, obj)})]
 
+    def get_inlines(self, request, obj):
+        """Hook for specifying custom inlines."""
+        return self.inlines
+
     def get_ordering(self, request):
         """
         Hook for specifying field ordering.
@@ -582,7 +586,7 @@ class ModelAdmin(BaseModelAdmin):
 
     def get_inline_instances(self, request, obj=None):
         inline_instances = []
-        for inline_class in self.inlines:
+        for inline_class in self.get_inlines(request, obj):
             inline = inline_class(self.model, self.admin_site)
             if request:
                 if not (inline.has_view_or_change_permission(request, obj) or

docs/ref/contrib/admin/index.txt

@@ -1627,6 +1627,16 @@ templates used by the :class:`ModelAdmin` views:
     instances of the classes defined in :attr:`inlines` or you might encounter
     a "Bad Request" error when adding related objects.
 
+.. method:: ModelAdmin.get_inlines(request, obj)
+
+    .. versionadded:: 3.0
+
+    The ``get_inlines`` method is given the ``HttpRequest`` and the
+    ``obj`` being edited (or ``None`` on an add form) and is expected to return
+    an iterable of inlines. You can override this method to dynamically add
+    inlines based on the request or model instance instead of specifying them
+    in :attr:`ModelAdmin.inlines`.
+
 .. method:: ModelAdmin.get_urls()
 
     The ``get_urls`` method on a ``ModelAdmin`` returns the URLs to be used for

docs/releases/3.0.txt

@@ -47,6 +47,10 @@ Minor features
 * Added support for the ``admin_order_field`` attribute on properties in
   :attr:`.ModelAdmin.list_display`.
 
+* The new :meth:`ModelAdmin.get_inlines()
+  <django.contrib.admin.ModelAdmin.get_inlines>` method allows specifying the
+  inlines based on the request or model instance.
+
 :mod:`django.contrib.admindocs`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/generic_inline_admin/tests.py

@@ -429,3 +429,29 @@ class GenericInlineModelAdminTest(SimpleTestCase):
         inlines = ma.get_inline_instances(request)
         for (formset, inline), other_inline in zip(ma.get_formsets_with_inlines(request), inlines):
             self.assertIsInstance(formset, other_inline.get_formset(request).__class__)
+
+    def test_get_inline_instances_override_get_inlines(self):
+        class MediaInline(GenericTabularInline):
+            model = Media
+
+        class AlternateInline(GenericTabularInline):
+            model = Media
+
+        class EpisodeAdmin(admin.ModelAdmin):
+            inlines = (AlternateInline, MediaInline)
+
+            def get_inlines(self, request, obj):
+                if hasattr(request, 'name'):
+                    if request.name == 'alternate':
+                        return self.inlines[:1]
+                    elif request.name == 'media':
+                        return self.inlines[1:2]
+                return []
+
+        ma = EpisodeAdmin(Episode, self.site)
+        self.assertEqual(ma.get_inlines(request, None), [])
+        self.assertEqual(ma.get_inline_instances(request), [])
+        for name, inline_class in (('alternate', AlternateInline), ('media', MediaInline)):
+            request.name = name
+            self.assertEqual(ma.get_inlines(request, None), (inline_class,)),
+            self.assertEqual(type(ma.get_inline_instances(request)[0]), inline_class)