Heading block attribute type issue

[metaphorcreations]

The Heading block is still using rich-text as the type for the content attribute and I am seeing the following warning:

Notice: Function rest_validate_value_from_schema was called incorrectly. The "type" schema keyword for content can only be one of the built-in types: array, object, string, number, integer, boolean, and null.

[mai21]

@metaphorcreations Thanks for reporting the issue. Can you please provide reproducible steps?

Note: Using ​https://wordpress.org/plugins/test-reports/ can help to add the needed info. Thanks

[metaphorcreations]

@mai21 I have a custom plugin that works with Gravity Forms and uses blocks to design email templates. This error occurs When a form is submitted and the blocks are rendered for the notifications. I haven't run into the issue when just using blocks on pages/posts, etc... So, it's quite a few steps to replicate.

But, I do know that many core blocks that WordPress loads from the wp-includes/blocks/blocks-json.php file contain "rich-text" types, which is causing the issue for my plugin.

Is there a reason why core block attributes are still using the "rich-text" type when it's not supported anymore?

The type field MUST be one of the following:

null
boolean
object
array
string
integer
number (same as integer)

[metaphorcreations]

@mai21 I created a short video showing the issue: ​https://www.loom.com/share/90390cf3151e40e6b20f67018955ea48?sid=6e592b3e-3eaf-411c-b387-d58e41fb34a3

[Mamaduka]

Hi, @metaphorcreations

Can you create an issue on the Gutenberg repo with reproduction steps? Link: ​https://github.com/WordPress/gutenberg/issues/new

The rich-text is a valid block attribute type.

[andfinally]

We are getting this issue in unit tests for RSS feeds. I believe this problem appeared after the WordPress 6.8 update.

When we include the markup of an image block in a test post, example below, the test fails, and we get the notice:

Notice: Function rest_validate_value_from_schema was called <strong>incorrectly</strong>. The "type" schema keyword for caption can only be one of the built-in types: array, object, string, number, integer, boolean, and null. Please see <a href="https://developer.wordpress.org/advanced-administration/debug/debug-wordpress/">Debugging in WordPress</a> for more information. (This message was added in version 5.5.0.) in /tmp/wordpress/wp-includes/functions.php on line 6114

<!-- wp:image {"url":"http://example.org/wp-content/uploads/2022/03/55038451-0-image-a-2_1646636766274.jpg?quality=90\u0026strip=all","caption":"Lorem ipsum","id":10853156,"sizeSlug":"full","linkDestination":"none"} -->

It looks like the following call stack is being run:

\do_blocks
-> \render_block
-> \WP_Block::render
-> \WP_Block::__get
-> \WP_Block_Type::prepare_attributes_for_render
-> \rest_validate_value_from_schema

When rest_validate_value_from_schema gets to the caption, the parameters are:

Value: Lorem ipsum
Schema: Array
(
    [type] => rich-text
    [source] => rich-text
    [selector] => figcaption
    [role] => content
)

This is validating the post content against the data types defined in the block.json file for the core/image block. There, rich-text is an acceptable type, as @Mamaduka says. But rest_validate_value_from_schema expects string, and complains.

To me, this doesn't look like a Gutenberg bug but an issue in the PHP.

It does seem weird that we validate block attributes against the types expected in a REST schema – the context is different. But apparently \WP_Block_Type::prepare_attributes_for_render has been calling rest_validate_value_from_schema since before WP 5.6.

[andfinally]

The rich-text type was added to the core image block.json in commit ​https://github.com/WordPress/WordPress/commit/1de40f71be71a2ae45fb615e06a2279b8ad363a0, which brought in Gutenberg 16.7 RC2. A bunch of other blocks also now have rich-text as the data type for attributes like caption.

The docs don't list rich-text as an allowed data type for block attributes: ​https://developer.wordpress.org/block-editor/reference-guides/block-api/block-attributes/#type-validation. rest_validate_value_from_schema follows this list. It validates attributes against this array.

$allowed_types = array( 'array', 'object', 'string', 'number', 'integer', 'boolean', 'null' );

The caption attribute of images is now rich-text, so blocks with this attribute fail the validation.

Maybe we need to stop using rest_validate_value_from_schema for non-REST contexts, or add a filter hook to it which allows developers to adjust the allowed types when needed.

[andfinally]

I have created ​https://github.com/WordPress/gutenberg/issues/72180 for this. It seems like an issue between WordPress and Gutenberg. Gutenberg has defined data types for image captions which WordPress block rendering doesn't expect.

Trac ticket: https://core.trac.wordpress.org/ticket/61406

Normalize rich-text block attribute type to string in WP_Block_Type::set_props()

Block attributes with type: "rich-text" (used in block.json for the editor) are not valid JSON Schema types. When WP_Block_Type::prepare_attributes_for_render() calls rest_validate_value_from_schema(), the unrecognised rich-text type triggers a _doing_it_wrong() notice:

The "type" schema keyword for content can only be one of the built-in types: array, object, string, number, integer, boolean, and null.

This affects all core blocks that define attributes as rich-text: paragraph, heading, list-item, image (caption), embed (caption), quote, pullquote, verse, code, preformatted, table, gallery, button, file, video, audio, details, and accordion-heading.

Changes in this PR:

1. src/wp-includes/class-wp-block-type.php — In set_props(), normalise rich-text to string at block registration time. This runs once (not per-render) and occurs before the register_block_type_args filter, so plugins can still override if needed.
2. tests/phpunit/tests/blocks/wpBlockType.php — Added a richtext attribute case to test_prepare_attributes() to verify that rich-text typed attributes pass validation without triggering _doing_it_wrong.

Related: Gutenberg issue ​https://github.com/WordPress/gutenberg/issues/72180

Maps rich-text block attribute schemas to string only for render-time REST validation, so WP_Block_Type::prepare_attributes_for_render() can validate those attributes without mutating registered block metadata.

This keeps non-string rich-text values rejected through the existing string validation path and preserves the registered rich-text schema after validation.

## Use of AI Tools

AI assistance: Yes
Tool(s): OpenAI Codex
Model(s): GPT-5
Used for: Implementing the patch, adding focused PHPUnit coverage, running validation commands, and preparing this PR.