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filter is not described

render_block_data filter-hook . WP 5.1.0

Filters the block being rendered in render_block(), before it's processed.

Usage

add_filter( 'render_block_data', 'filter_function_name_837', 10, 2 );
function filter_function_name_837( $block, $source_block ){
	// filter...

	return $block;
}
$block(array)
The block being rendered.
$source_block(array)
An un-modified copy of $block, as it appeared in the source content.

Where the hook is called

render_block()
render_block_data
wp-includes/blocks.php 201
$block = apply_filters( 'render_block_data', $block, $source_block );

Where the hook is used (in WP core)

Does not used.