From e4748e45de4fedc60cb428d91fa94d4cc24e410d Mon Sep 17 00:00:00 2001
From: Sage Abdullah <sage.abdullah@torchbox.com>
Date: Wed, 29 Jan 2025 15:21:32 +0000
Subject: [PATCH] Fix Block.is_previewable detection on blocks with non-None
unset default values
---
wagtail/blocks/base.py | 6 +++++-
wagtail/blocks/list_block.py | 3 ++-
wagtail/blocks/stream_block.py | 4 ++++
wagtail/blocks/struct_block.py | 4 ++++
wagtail/tests/test_blocks.py | 11 +++++++++++
5 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/wagtail/blocks/base.py b/wagtail/blocks/base.py
index e0128ba9af..c37d359a56 100644
--- a/wagtail/blocks/base.py
+++ b/wagtail/blocks/base.py
@@ -298,6 +298,10 @@ class Block(metaclass=BaseBlock):
return self.normalize(self.meta.preview_value)
return self.get_default()
+ @cached_property
+ def _has_default(self):
+ return getattr(self.meta, "default", None) is not None
+
@cached_property
def is_previewable(self):
# To prevent showing a broken preview if the block preview has not been
@@ -314,7 +318,7 @@ class Block(metaclass=BaseBlock):
)
has_preview_value = (
hasattr(self.meta, "preview_value")
- or getattr(self.meta, "default", None) is not None
+ or self._has_default
or self.__class__.get_preview_context is not Block.get_preview_context
or self.__class__.get_preview_value is not Block.get_preview_value
)
diff --git a/wagtail/blocks/list_block.py b/wagtail/blocks/list_block.py
index 3fcbdcff9e..c7505e387e 100644
--- a/wagtail/blocks/list_block.py
+++ b/wagtail/blocks/list_block.py
@@ -147,7 +147,8 @@ class ListBlock(Block):
else:
self.child_block = child_block
- if not hasattr(self.meta, "default"):
+ self._has_default = hasattr(self.meta, "default")
+ if not self._has_default:
# Default to a list consisting of one empty (i.e. default-valued) child item
self.meta.default = [self.child_block.get_default()]
diff --git a/wagtail/blocks/stream_block.py b/wagtail/blocks/stream_block.py
index a8ab0f7010..6c38789e83 100644
--- a/wagtail/blocks/stream_block.py
+++ b/wagtail/blocks/stream_block.py
@@ -460,6 +460,10 @@ class BaseStreamBlock(Block):
return errors
+ @cached_property
+ def _has_default(self):
+ return self.meta.default is not BaseStreamBlock._meta_class.default
+
class Meta:
# No icon specified here, because that depends on the purpose that the
# block is being used for. Feel encouraged to specify an icon in your
diff --git a/wagtail/blocks/struct_block.py b/wagtail/blocks/struct_block.py
index 05a717cb8c..a4e8f93d23 100644
--- a/wagtail/blocks/struct_block.py
+++ b/wagtail/blocks/struct_block.py
@@ -382,6 +382,10 @@ class BaseStructBlock(Block):
"prefix": prefix,
}
+ @cached_property
+ def _has_default(self):
+ return self.meta.default is not BaseStructBlock._meta_class.default
+
class Meta:
default = {}
form_classname = "struct-block"
diff --git a/wagtail/tests/test_blocks.py b/wagtail/tests/test_blocks.py
index 3ef4b6c556..6dc4ee0a5a 100644
--- a/wagtail/tests/test_blocks.py
+++ b/wagtail/tests/test_blocks.py
@@ -93,6 +93,11 @@ class TestBlock(SimpleTestCase):
"specific_template_and_custom_value": [
blocks.Block(preview_template="foo.html", preview_value="bar"),
],
+ "unset_default_not_none": [
+ blocks.ListBlock(blocks.Block()),
+ blocks.StreamBlock(),
+ blocks.StructBlock(),
+ ],
}
# Test without a global template override
@@ -109,6 +114,9 @@ class TestBlock(SimpleTestCase):
# Providing both a preview template and value also makes the block
# previewable, this is the same as providing a custom template only
("specific_template_and_custom_value", True),
+ # These blocks define their own unset default value that is not
+ # `None`, and that value should not make it previewable
+ ("unset_default_not_none", False),
]
for variant, is_previewable in cases:
with self.subTest(variant=variant, custom_global_template=False):
@@ -134,6 +142,9 @@ class TestBlock(SimpleTestCase):
("custom_value", True),
# Unchanged – providing both also makes the block previewable
("specific_template_and_custom_value", True),
+ # Unchanged – even after providing a global template override,
+ # these blocks should not be previewable
+ ("unset_default_not_none", False),
]
for variant, is_previewable in cases:
with self.subTest(variant=variant, custom_global_template=True):