Fixed #35606, Refs #34045 -- Fixed rendering of ModelAdmin.action_checkbox for models with a __html__ method.

Thank you Claude Paroz for the report.

Regression in 85366fbca723c9b37d0ac9db1d44e3f1cb188db2.

2 files changed, 33 insertions, 0 deletions

diff --git a/tests/admin_changelist/models.py b/tests/admin_changelist/models.py
index 290a3ea4ec..78e65ab878 100644
--- a/tests/admin_changelist/models.py
+++ b/tests/admin_changelist/models.py
@@ -23,6 +23,12 @@ class GrandChild(models.Model):
     parent = models.ForeignKey(Child, models.SET_NULL, editable=False, null=True)
     name = models.CharField(max_length=30, blank=True)
 
+    def __str__(self):
+        return self.name
+
+    def __html__(self):
+        return f'<h2 class="main">{self.name}</h2>'
+
 
 class Genre(models.Model):
     name = models.CharField(max_length=20)
diff --git a/tests/admin_changelist/tests.py b/tests/admin_changelist/tests.py
index bf85cf038f..4d8845e11e 100644
--- a/tests/admin_changelist/tests.py
+++ b/tests/admin_changelist/tests.py
@@ -364,6 +364,33 @@ class ChangeListTests(TestCase):
             table_output,
         )
 
+    def test_action_checkbox_for_model_with_dunder_html(self):
+        grandchild = GrandChild.objects.create(name="name")
+        request = self._mocked_authenticated_request("/grandchild/", self.superuser)
+        m = GrandChildAdmin(GrandChild, custom_site)
+        cl = m.get_changelist_instance(request)
+        cl.formset = None
+        template = Template(
+            "{% load admin_list %}{% spaceless %}{% result_list cl %}{% endspaceless %}"
+        )
+        context = Context({"cl": cl, "opts": GrandChild._meta})
+        table_output = template.render(context)
+        link = reverse(
+            "admin:admin_changelist_grandchild_change", args=(grandchild.id,)
+        )
+        row_html = build_tbody_html(
+            grandchild,
+            link,
+            "name",
+            '<td class="field-parent__name">-</td>'
+            '<td class="field-parent__parent__name">-</td>',
+        )
+        self.assertNotEqual(
+            table_output.find(row_html),
+            -1,
+            "Failed to find expected row element: %s" % table_output,
+        )
+
     def test_result_list_editable_html(self):
         """
         Regression tests for #11791: Inclusion tag result_list generates a