try with role: content in block attributes

packages/block-editor/src/components/block-switcher/pattern-transformations-menu.js

@@ -5,7 +5,10 @@ import { __ } from '@wordpress/i18n';
 import { useState, useMemo } from '@wordpress/element';
 import { useInstanceId } from '@wordpress/compose';
 import { chevronRight } from '@wordpress/icons';
-import { cloneBlock, getBlockTransforms } from '@wordpress/blocks';
+import {
+	cloneBlock,
+	__experimentalGetBlockAttributesNamesByRole as getBlockAttributesNamesByRole,
+} from '@wordpress/blocks';
 import {
 	MenuGroup,
 	MenuItem,
@@ -105,19 +108,17 @@ function PatternTransformationsMenu( {
 							transformedBlocksSet
 						);
 						if ( ! match ) return;
-						// Found a match, so get the `retainAttributes` from
-						// block type's transforms to retain these and keep
-						// everything else from the pattern's block.
-						// If `retainAttributes` are not set, update the match
-						// with all the selected block's attributes.
-						const retainAttributes = getBlockTransforms(
-							'to',
-							block.name
-						).find( ( { type } ) => type === 'pattern' )
-							?.retainAttributes;
+						// Found a match, so find and retain block attributes
+						// with `content` role. Everything else comes from the
+						// pattern's block. If no `content` attributes found,
+						// update the match with all the selected block's attributes.
+						const contentAttributes = getBlockAttributesNamesByRole(
+							block.name,
+							'content'
+						);
 						let retainedBlockAttributes = block.attributes;
-						if ( retainAttributes?.length ) {
-							retainedBlockAttributes = retainAttributes.reduce(
+						if ( contentAttributes?.length ) {
+							retainedBlockAttributes = contentAttributes.reduce(
 								( _accumulator, attribute ) => {
 									if ( block.attributes[ attribute ] )
 										_accumulator[ attribute ] =

packages/block-library/src/heading/block.json

@@ -10,7 +10,8 @@
 			"type": "string",
 			"source": "html",
 			"selector": "h1,h2,h3,h4,h5,h6",
-			"default": ""
+			"default": "",
+			"role": "content"
 		},
 		"level": {
 			"type": "number",

packages/block-library/src/heading/transforms.js

@@ -91,7 +91,6 @@ const transforms = {
 					} )
 				),
 		},
-		{ type: 'pattern', retainAttributes: [ 'content' ] },
 	],
 };
 

packages/block-library/src/paragraph/block.json

@@ -10,7 +10,8 @@
 			"type": "string",
 			"source": "html",
 			"selector": "p",
-			"default": ""
+			"default": "",
+			"role": "content"
 		},
 		"dropCap": {
 			"type": "boolean",

packages/block-library/src/paragraph/transforms.js

@@ -37,7 +37,6 @@ const transforms = {
 			},
 		},
 	],
-	to: [ { type: 'pattern', retainAttributes: [ 'content' ] } ],
 };
 
 export default transforms;

packages/blocks/src/api/index.js

@@ -141,6 +141,7 @@ export {
 	getBlockLabel as __experimentalGetBlockLabel,
 	getAccessibleBlockLabel as __experimentalGetAccessibleBlockLabel,
 	__experimentalSanitizeBlockAttributes,
+	__experimentalGetBlockAttributesNamesByRole,
 } from './utils';
 
 // Templates are, in a general sense, a basic collection of block nodes with any

packages/blocks/src/api/utils.js

@@ -275,3 +275,24 @@ export function __experimentalSanitizeBlockAttributes( name, attributes ) {
 		{}
 	);
 }
+
+/**
+ * I created this wrapper to hide the complexity for the consumer..
+ *
+ * @param {*} name
+ * @param {*} role
+ */
+// TODO jsdoc
+// TODO tests
+export function __experimentalGetBlockAttributesNamesByRole( name, role ) {
+	const attributes = getBlockType( name )?.attributes;
+	if ( ! attributes ) return;
+	if ( ! role ) return Object.keys( attributes );
+	return Object.entries( attributes ).reduce(
+		( accumulator, [ attributeName, schema ] ) => {
+			if ( schema?.role === role ) accumulator.push( attributeName );
+			return accumulator;
+		},
+		[]
+	);
+}