Fixed #18263 -- Corrrected handling of hidden fields in tabular admin inlines.

Thanks hvdklauw for the report and patch.

django/contrib/admin/templates/admin/edit_inline/tabular.html

@@ -35,7 +35,7 @@
           {% for fieldset in inline_admin_form %}
             {% for line in fieldset %}
               {% for field in line %}
-                {% if field.is_hidden %} {{ field.field }} {% endif %}
+                {% if field.field.is_hidden %} {{ field.field }} {% endif %}
               {% endfor %}
             {% endfor %}
           {% endfor %}
@@ -44,6 +44,7 @@
         {% for fieldset in inline_admin_form %}
           {% for line in fieldset %}
             {% for field in line %}
+              {% if not field.field.is_hidden %}
               <td{% if field.field.name %} class="field-{{ field.field.name }}"{% endif %}>
               {% if field.is_readonly %}
                   <p>{{ field.contents|linebreaksbr }}</p>
@@ -52,6 +53,7 @@
                   {{ field.field }}
               {% endif %}
               </td>
+              {% endif %}
             {% endfor %}
           {% endfor %}
         {% endfor %}

tests/admin_inlines/admin.py

@@ -165,6 +165,22 @@ class BinaryTreeAdmin(admin.TabularInline):
 class SightingInline(admin.TabularInline):
     model = Sighting
 
+# admin and form for #18263
+class SomeChildModelForm(forms.ModelForm):
+
+    class Meta:
+        fields = '__all__'
+        model = SomeChildModel
+        widgets = {
+            'position': forms.HiddenInput,
+        }
+
+
+class SomeChildModelInline(admin.TabularInline):
+    model = SomeChildModel
+    form = SomeChildModelForm
+
+
 site.register(TitleCollection, inlines=[TitleInline])
 # Test bug #12561 and #12778
 # only ModelAdmin media
@@ -184,3 +200,4 @@ site.register(ProfileCollection, inlines=[ProfileInline])
 site.register(ParentModelWithCustomPk, inlines=[ChildModel1Inline, ChildModel2Inline])
 site.register(BinaryTree, inlines=[BinaryTreeAdmin])
 site.register(ExtraTerrestrial, inlines=[SightingInline])
+site.register(SomeParentModel, inlines=[SomeChildModelInline])

tests/admin_inlines/models.py

@@ -221,6 +221,17 @@ class Sighting(models.Model):
     et = models.ForeignKey(ExtraTerrestrial)
     place = models.CharField(max_length=100)
 
+
+# Models for #18263
+class SomeParentModel(models.Model):
+    name = models.CharField(max_length=1)
+
+
+class SomeChildModel(models.Model):
+    name = models.CharField(max_length=1)
+    position = models.PositiveIntegerField()
+    parent = models.ForeignKey(SomeParentModel)
+
 # Other models
 
 class ProfileCollection(models.Model):

tests/admin_inlines/tests.py

@@ -12,7 +12,8 @@ from .admin import InnerInline
 from .models import (Holder, Inner, Holder2, Inner2, Holder3, Inner3, Person,
     OutfitItem, Fashionista, Teacher, Parent, Child, Author, Book, Profile,
     ProfileCollection, ParentModelWithCustomPk, ChildModel1, ChildModel2,
-    Sighting, Novel, Chapter, FootNote, BinaryTree)
+    Sighting, Novel, Chapter, FootNote, BinaryTree, SomeParentModel,
+    SomeChildModel)
 
 
 @override_settings(PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',))
@@ -126,6 +127,16 @@ class TestInline(TestCase):
         response = self.client.get('/admin/admin_inlines/capofamiglia/add/')
         self.assertContains(response, '<img src="/static/admin/img/icon-unknown.gif" class="help help-tooltip" width="10" height="10" alt="(Help text for ReadOnlyInline)" title="Help text for ReadOnlyInline" />', 1)
 
+    def test_inline_hidden_field_no_column(self):
+        """#18263 -- Make sure hidden fields don't get a column in tabular inlines"""
+        parent = SomeParentModel.objects.create(name='a')
+        SomeChildModel.objects.create(name='b', position='0', parent=parent)
+        SomeChildModel.objects.create(name='c', position='1', parent=parent)
+        response = self.client.get('/admin/admin_inlines/someparentmodel/%s/' % parent.pk)
+        self.assertNotContains(response, '<td class="field-position">')
+        self.assertContains(response, (
+            '<input id="id_somechildmodel_set-1-position" '
+            'name="somechildmodel_set-1-position" type="hidden" value="1" />'))
 
     def test_non_related_name_inline(self):
         """