Fixed #27991 -- Added obj arg to InlineModelAdmin.has_add_permission().

Thanks Vladimir Ivanov for the initial patch.

django/contrib/admin/checks.py

@@ -1,3 +1,4 @@
+import warnings
 from itertools import chain
 
 from django.apps import apps
@@ -13,6 +14,8 @@ from django.forms.models import (
     BaseModelForm, BaseModelFormSet, _get_foreign_key,
 )
 from django.template.engine import Engine
+from django.utils.deprecation import RemovedInDjango30Warning
+from django.utils.inspect import get_func_args
 
 
 def check_admin_app(app_configs, **kwargs):
@@ -884,6 +887,7 @@ class ModelAdminChecks(BaseModelAdminChecks):
 class InlineModelAdminChecks(BaseModelAdminChecks):
 
     def check(self, inline_obj, **kwargs):
+        self._check_has_add_permission(inline_obj)
         parent_model = inline_obj.parent_model
         return [
             *super().check(inline_obj),
@@ -968,6 +972,20 @@ class InlineModelAdminChecks(BaseModelAdminChecks):
         else:
             return []
 
+    def _check_has_add_permission(self, obj):
+        cls = obj.__class__
+        try:
+            func = cls.has_add_permission
+        except AttributeError:
+            pass
+        else:
+            args = get_func_args(func)
+            if 'obj' not in args:
+                warnings.warn(
+                    "Update %s.has_add_permission() to accept a positional "
+                    "`obj` argument." % cls.__name__, RemovedInDjango30Warning
+                )
+
 
 def must_be(type, option, obj, id):
     return [

django/contrib/admin/options.py

@@ -44,6 +44,7 @@ from django.urls import reverse
 from django.utils.decorators import method_decorator
 from django.utils.html import format_html
 from django.utils.http import urlencode
+from django.utils.inspect import get_func_args
 from django.utils.safestring import mark_safe
 from django.utils.text import capfirst, format_lazy, get_text_list
 from django.utils.translation import gettext as _, ngettext
@@ -559,12 +560,18 @@ class ModelAdmin(BaseModelAdmin):
         inline_instances = []
         for inline_class in self.inlines:
             inline = inline_class(self.model, self.admin_site)
+            # RemovedInDjango30Warning: obj will be a required argument.
+            args = get_func_args(inline.has_add_permission)
+            if 'obj' in args:
+                inline_has_add_permission = inline.has_add_permission(request, obj)
+            else:
+                inline_has_add_permission = inline.has_add_permission(request)
             if request:
-                if not (inline.has_add_permission(request) or
+                if not (inline_has_add_permission or
                         inline.has_change_permission(request, obj) or
                         inline.has_delete_permission(request, obj)):
                     continue
-                if not inline.has_add_permission(request):
+                if not inline_has_add_permission:
                     inline.max_num = 0
             inline_instances.append(inline)
 
@@ -2007,13 +2014,13 @@ class InlineModelAdmin(BaseModelAdmin):
             queryset = queryset.none()
         return queryset
 
-    def has_add_permission(self, request):
+    def has_add_permission(self, request, obj):
         if self.opts.auto_created:
             # We're checking the rights to an auto-created intermediate model,
             # which doesn't have its own individual permissions. The user needs
             # to have the change permission for the related model in order to
             # be able to do anything with the intermediate model.
-            return self.has_change_permission(request)
+            return self.has_change_permission(request, obj)
         return super().has_add_permission(request)
 
     def has_change_permission(self, request, obj=None):

docs/internals/deprecation.txt

@@ -41,6 +41,9 @@ details on these changes.
 
 * ``django.contrib.staticfiles.templatetags.static()`` will be removed.
 
+* The shim to allow ``InlineModelAdmin.has_add_permission()`` to be defined
+  without an ``obj`` argument will be removed.
+
 .. _deprecation-removed-in-2.1:
 
 2.1

docs/ref/contrib/admin/index.txt

@@ -2395,10 +2395,15 @@ The ``InlineModelAdmin`` class adds or customizes:
     inline forms. For example, this may be based on the model instance
     (passed as the keyword argument ``obj``).
 
-.. method:: InlineModelAdmin.has_add_permission(request)
+.. method:: InlineModelAdmin.has_add_permission(request, obj)
 
     Should return ``True`` if adding an inline object is permitted, ``False``
-    otherwise.
+    otherwise. ``obj`` is the parent object being edited or ``None`` when
+    adding a new parent.
+
+    .. versionchanged:: 2.1
+
+        The ``obj`` argument was added.
 
 .. method:: InlineModelAdmin.has_change_permission(request, obj=None)
 

docs/releases/2.1.txt

@@ -64,6 +64,9 @@ Minor features
   with ``change_list_object_tools.html`` and
   ``change_form_object_tools.html`` templates.
 
+* :meth:`.InlineModelAdmin.has_add_permission` is now passed the parent object
+  as the second positional argument, ``obj``.
+
 :mod:`django.contrib.admindocs`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -398,6 +401,10 @@ Miscellaneous
 * ``django.contrib.staticfiles.templatetags.static()`` is deprecated in favor
   of ``django.templatetags.static.static()``.
 
+* Support for :meth:`.InlineModelAdmin.has_add_permission` methods that don't
+  accept ``obj`` as the second positional argument will be removed in Django
+  3.0.
+
 .. _removed-features-2.1:
 
 Features removed in 2.1

tests/modeladmin/test_has_add_permission_obj_deprecation.py

@@ -0,0 +1,63 @@
+import warnings
+
+from django.contrib.admin.options import ModelAdmin, TabularInline
+from django.utils.deprecation import RemovedInDjango30Warning
+
+from .models import Band, Song
+from .test_checks import CheckTestCase
+
+
+class HasAddPermissionObjTests(CheckTestCase):
+    def test_model_admin_inherited_valid(self):
+        class BandAdmin(ModelAdmin):
+            pass
+
+        self.assertIsValid(BandAdmin, Band)
+
+    def test_model_admin_valid(self):
+        class BandAdmin(ModelAdmin):
+            def has_add_permission(self, request):
+                return super().has_add_permission(request)
+
+        self.assertIsValid(BandAdmin, Band)
+
+    def test_inline_admin_inherited_valid(self):
+        class SongInlineAdmin(TabularInline):
+            model = Song
+
+        class BandAdmin(ModelAdmin):
+            inlines = [SongInlineAdmin]
+
+        self.assertIsValid(BandAdmin, Band)
+
+    def test_inline_admin_valid(self):
+        class SongInlineAdmin(TabularInline):
+            model = Song
+
+            def has_add_permission(self, request, obj):
+                return super().has_add_permission(request, obj)
+
+        class BandAdmin(ModelAdmin):
+            inlines = [SongInlineAdmin]
+
+        self.assertIsValid(BandAdmin, Band)
+
+    def test_inline_admin_warning(self):
+        class SongInlineAdmin(TabularInline):
+            model = Song
+
+            def has_add_permission(self, request):
+                return super().has_add_permission(request)
+
+        class BandAdmin(ModelAdmin):
+            inlines = [SongInlineAdmin]
+
+        with warnings.catch_warnings(record=True) as recorded:
+            warnings.simplefilter('always')
+            self.assertIsValid(BandAdmin, Band)
+        self.assertEqual(len(recorded), 1)
+        self.assertIs(recorded[0].category, RemovedInDjango30Warning)
+        self.assertEqual(str(recorded[0].message), (
+            "Update SongInlineAdmin.has_add_permission() to accept a "
+            "positional `obj` argument."
+        ))

tests/modeladmin/tests.py

@@ -709,6 +709,25 @@ class ModelAdminPermissionTests(SimpleTestCase):
         request.user = self.MockDeleteUser()
         self.assertFalse(ma.has_add_permission(request))
 
+    def test_inline_has_add_permission_uses_obj(self):
+        class ConcertInline(TabularInline):
+            model = Concert
+
+            def has_add_permission(self, request, obj):
+                return bool(obj)
+
+        class BandAdmin(ModelAdmin):
+            inlines = [ConcertInline]
+
+        ma = BandAdmin(Band, AdminSite())
+        request = MockRequest()
+        request.user = self.MockAddUser()
+        self.assertEqual(ma.get_inline_instances(request), [])
+        band = Band(name='The Doors', bio='', sign_date=date(1965, 1, 1))
+        inline_instances = ma.get_inline_instances(request, band)
+        self.assertEqual(len(inline_instances), 1)
+        self.assertIsInstance(inline_instances[0], ConcertInline)
+
     def test_has_change_permission(self):
         """
         has_change_permission returns True for users who can edit objects and