12780 Provide a hook for compound form/formset validation in ModelAdmin

django/contrib/admin/options.py

@@ -1815,7 +1815,9 @@ def _changeform_view(self, request, object_id, form_url, extra_context):
                 new_object = self.save_form(request, form, change=not add)
             else:
                 new_object = form.instance
-            if all_valid(formsets) and form_validated:
+            all_formsets_valid = all_valid(formsets)
+            change_form_valid = self.is_change_form_valid(request, form, formsets, add)
+            if all_formsets_valid and form_validated and change_form_valid:
                 self.save_model(request, new_object, form, not add)
                 self.save_related(request, form, formsets, not add)
                 change_message = self.construct_change_message(
@@ -1903,6 +1905,13 @@ def _changeform_view(self, request, object_id, form_url, extra_context):
             request, context, add=add, change=not add, obj=obj, form_url=form_url
         )
 
+    def is_change_form_valid(self, request, form, formsets, add):
+        """
+        Hook for doing extra form validation. Return True if valid, False
+        otherwise. Called in response to a POST request.
+        """
+        return True
+
     def add_view(self, request, form_url="", extra_context=None):
         return self.changeform_view(request, None, form_url, extra_context)
 

docs/ref/contrib/admin/index.txt

@@ -2012,6 +2012,29 @@ templates used by the :class:`ModelAdmin` views:
         def get_changeform_initial_data(self, request):
             return {"name": "custom_initial_value"}
 
+.. method:: ModelAdmin.is_change_form_valid(request, form, formsets, add)
+
+    .. versionadded:: 5.0
+
+    A hook for customizing the validation of the change form as a whole.
+    By default, it return True.
+    You have access to the request, the form, the formsets and a boolean add.
+
+    This method should return a boolean value::
+
+        def is_change_form_valid(self, request, form, formsets, add):
+
+            has_special_name_in_form = form.cleaned_data["name"] == "Special name"
+            has_special_name_in_formset = any(
+                formset.cleaned_data["related_name"] == "Special name" for formset in formsets
+            )
+            if has_special_name_in_form and has_special_name_in_formset:
+                # add an error to the form to inform the user
+                form.add_error(None, 'Can not have "Special name" as a name and a related name')
+                return False
+            return True
+
+
 .. method:: ModelAdmin.get_deleted_objects(objs, request)
 
     A hook for customizing the deletion process of the :meth:`delete_view` and

docs/releases/5.0.txt

@@ -122,6 +122,9 @@ Minor features
   ``RelatedOnlyFieldListFilter`` admin filters now handle multi-valued query
   parameters.
 
+* The new :meth:`.ModelAdmin.is_change_form_valid` method provides
+  a hook for compound form/formset validation.
+
 :mod:`django.contrib.admindocs`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/admin_views/admin.py

@@ -1023,6 +1023,15 @@ class DependentChildInline(admin.TabularInline):
 class ParentWithDependentChildrenAdmin(admin.ModelAdmin):
     inlines = [DependentChildInline]
 
+    def is_change_form_valid(self, request, form, formsets, add):
+        if form.cleaned_data.get("family_name") == "Foo" and len(formsets) > 0:
+            form.add_error(
+                "family_name",
+                "The name 'Foo' with depends is not allowed is this test case.",
+            )
+            return False
+        return True
+
 
 # Tests for ticket 11277 ----------------------------------
 

tests/admin_views/tests.py

@@ -8234,6 +8234,40 @@ def test_change_view_form_and_formsets_run_validation(self):
             ],
         )
 
+    def test_change_view_whole_form_validation(self):
+        """
+        Issue #12780
+        Verifying that is_change_form_valid hook is called.
+        """
+        pwdc = ParentWithDependentChildren.objects.create(
+            some_required_info=6, family_name="Foo"
+        )
+        # The validation should fail because we're not allowing the name 'Foo' to have
+        # depends, asserting that is_change_form_valid is called and have access to
+        # the form and to formsets.
+
+        post_data = {
+            "family_name": "Foo",
+            "some_required_info": "4",
+            "dependentchild_set-TOTAL_FORMS": "1",
+            "dependentchild_set-INITIAL_FORMS": "0",
+            "dependentchild_set-MAX_NUM_FORMS": "1",
+            "dependentchild_set-0-id": "",
+            "dependentchild_set-0-parent": str(pwdc.id),
+            "dependentchild_set-0-family_name": "Foo",
+        }
+        response = self.client.post(
+            reverse(
+                "admin:admin_views_parentwithdependentchildren_change", args=(pwdc.id,)
+            ),
+            post_data,
+        )
+        self.assertFormError(
+            response.context["adminform"],
+            "family_name",
+            ["The name 'Foo' with depends is not allowed is this test case."],
+        )
+
     def test_check(self):
         "The view_on_site value is either a boolean or a callable"
         try: