[2.1.x] Fixed #29414 -- Restored form inputs on admin inlines when the user doesn't have the change permission.

Regression in 825f0beda8.
Backport of ffb72a95bc from master

django/contrib/admin/helpers.py

@@ -244,9 +244,10 @@ class InlineAdminFormSet:
         self.has_view_permission = has_view_permission
 
     def __iter__(self):
-        readonly_fields_for_editing = self.readonly_fields
-        if not self.has_change_permission:
-            readonly_fields_for_editing += flatten_fieldsets(self.fieldsets)
+        if self.has_change_permission:
+            readonly_fields_for_editing = self.readonly_fields
+        else:
+            readonly_fields_for_editing = self.readonly_fields + flatten_fieldsets(self.fieldsets)
 
         for form, original in zip(self.formset.initial_forms, self.formset.get_queryset()):
             view_on_site_url = self.opts.get_view_on_site_url(original)

tests/admin_inlines/admin.py

@@ -7,9 +7,9 @@ from .models import (
     Consigliere, EditablePKBook, ExtraTerrestrial, Fashionista, Holder,
     Holder2, Holder3, Holder4, Inner, Inner2, Inner3, Inner4Stacked,
     Inner4Tabular, NonAutoPKBook, NonAutoPKBookChild, Novel,
-    ParentModelWithCustomPk, Poll, Profile, ProfileCollection, Question,
-    ReadOnlyInline, ShoppingWeakness, Sighting, SomeChildModel,
-    SomeParentModel, SottoCapo, Title, TitleCollection,
+    NovelReadonlyChapter, ParentModelWithCustomPk, Poll, Profile,
+    ProfileCollection, Question, ReadOnlyInline, ShoppingWeakness, Sighting,
+    SomeChildModel, SomeParentModel, SottoCapo, Title, TitleCollection,
 )
 
 site = admin.AdminSite(name="admin")
@@ -153,6 +153,17 @@ class NovelAdmin(admin.ModelAdmin):
     inlines = [ChapterInline]
 
 
+class ReadOnlyChapterInline(admin.TabularInline):
+    model = Chapter
+
+    def has_change_permission(self, request, obj=None):
+        return False
+
+
+class NovelReadonlyChapterAdmin(admin.ModelAdmin):
+    inlines = [ReadOnlyChapterInline]
+
+
 class ConsigliereInline(admin.TabularInline):
     model = Consigliere
 
@@ -231,6 +242,7 @@ site.register(Holder3, inlines=[InnerInline3])
 
 site.register(Poll, PollAdmin)
 site.register(Novel, NovelAdmin)
+site.register(NovelReadonlyChapter, NovelReadonlyChapterAdmin)
 site.register(Fashionista, inlines=[InlineWeakness])
 site.register(Holder4, Holder4Admin)
 site.register(Author, AuthorAdmin)

tests/admin_inlines/models.py

@@ -159,6 +159,12 @@ class Novel(models.Model):
     name = models.CharField(max_length=40)
 
 
+class NovelReadonlyChapter(Novel):
+
+    class Meta:
+        proxy = True
+
+
 class Chapter(models.Model):
     name = models.CharField(max_length=40)
     novel = models.ForeignKey(Novel, models.CASCADE)

tests/admin_inlines/tests.py

@@ -447,6 +447,16 @@ class TestInline(TestDataMixin, TestCase):
         self.assertTrue(response.context['inline_admin_formset'].opts.has_registered_model)
         self.assertNotContains(response, INLINE_CHANGELINK_HTML)
 
+    def test_noneditable_inline_has_field_inputs(self):
+        """Inlines without change permission shows field inputs on add form."""
+        response = self.client.get(reverse('admin:admin_inlines_novelreadonlychapter_add'))
+        self.assertContains(
+            response,
+            '<input type="text" name="chapter_set-0-name" '
+            'class="vTextField" maxlength="40" id="id_chapter_set-0-name">',
+            html=True
+        )
+
 
 @override_settings(ROOT_URLCONF='admin_inlines.urls')
 class TestInlineMedia(TestDataMixin, TestCase):