From 98fdc66d1a38892b907fd41178086ab1972eb270 Mon Sep 17 00:00:00 2001
From: Johannes Raggam <thetetet@gmail.com>
Date: Thu, 19 Feb 2026 21:38:41 +0100
Subject: [PATCH] Allow to create content with `index_html` id on the site
 root.

The portal root has a `index_html` method which prevented content with the id
`index_html` to be created and used as a default page.

Fixes: https://github.com/plone/Products.CMFPlone/issues/4278
---
 news/4278.bugfix.rst               |  8 +++++
 src/plone/base/tests/test_utils.py | 55 ++++++++++++++++++++++++++++++
 src/plone/base/utils.py            |  7 ++--
 3 files changed, 67 insertions(+), 3 deletions(-)
 create mode 100644 news/4278.bugfix.rst

diff --git a/news/4278.bugfix.rst b/news/4278.bugfix.rst
new file mode 100644
index 0000000..5869b19
--- /dev/null
+++ b/news/4278.bugfix.rst
@@ -0,0 +1,8 @@
+Allow to create content with `index_html` id on the site root.
+
+The portal root has a `index_html` method which prevented content with the id
+`index_html` to be created and used as a default page.
+
+Fixes: https://github.com/plone/Products.CMFPlone/issues/4278
+
+@thet
diff --git a/src/plone/base/tests/test_utils.py b/src/plone/base/tests/test_utils.py
index e9f8bac..6a5e0a5 100644
--- a/src/plone/base/tests/test_utils.py
+++ b/src/plone/base/tests/test_utils.py
@@ -217,3 +217,58 @@ def test_is_truthy(self):
         self.assertFalse(is_truthy("NO"))
         self.assertFalse(is_truthy("no"))
         self.assertFalse(is_truthy("foo"))
+
+    def test_check_for_collision(self):
+        from plone.base.utils import _check_for_collision
+
+        class Container(dict):
+            def __getattribute__(self, name):
+                if name in self:
+                    return self[name]
+                return object.__getattribute__(self, name)
+
+            def portal_type(self):
+                """Necessary to fulfill protocol."""
+
+            def index_html(self):
+                """Common attribute - content with id index_html should be
+                addable."""
+
+            def some_attr(self):
+                """Random attribute - content with id some_attr should not be
+                addable."""
+
+        container = Container()
+        container["test"] = Container()
+
+        # "test" is already taken
+        self.assertIn(
+            "There is already an item named",
+            _check_for_collision(container, "test"),
+        )
+
+        # "tiptop" is not yet taken
+        self.assertEqual(
+            _check_for_collision(container, "tiptop"),
+            None,
+        )
+
+        # "index_html" is not yet taken
+        self.assertEqual(
+            _check_for_collision(container, "index_html"),
+            None,
+        )
+
+        container["index_html"] = Container()
+
+        # `False` as "index_html" is now taken
+        self.assertIn(
+            "There is already an item named",
+            _check_for_collision(container, "index_html"),
+        )
+
+        # Content ids are not addable, if the id is an container attribute.
+        self.assertIn(
+            "is reserved",
+            _check_for_collision(container, "some_attr"),
+        )
diff --git a/src/plone/base/utils.py b/src/plone/base/utils.py
index 8a79d27..97a4cea 100644
--- a/src/plone/base/utils.py
+++ b/src/plone/base/utils.py
@@ -506,6 +506,10 @@ def _check_for_collision(contained_by, cid, **kwargs):
                 mapping={"name": cid},
             )
 
+    if cid == "index_html":
+        # always allow index_html
+        return
+
     # containers may have a field / attribute of the same name
     if base_hasattr(contained_by, cid):
         return _("${name} is reserved.", mapping={"name": cid})
@@ -533,9 +537,6 @@ def _check_for_collision(contained_by, cid, **kwargs):
     # However, we do want to allow overriding of *content* in the object's
     # parent path, including the portal root.
 
-    if cid == "index_html":
-        # always allow index_html
-        return
     portal = getSite()
     if portal and cid in portal.contentIds():
         # Fine to use the same id as a *content* item from the root.