[Block Attributes]: Add support for non-duplicable block attributes

docs/reference-guides/block-api/block-attributes.md

@@ -167,6 +167,23 @@ _Example_: Extract `src` and `alt` from each image element in the block's markup
 // }
 ```
 
+## Duplicable Attributes
+
+The `duplicable` key is used to indicate whether a block attribute should be copied when a block is duplicated. If an attribute sets the `duplicable` key to `false`, its value will not be copied, and it will instead fall back to the default value if one is supplied. If the key is not explicitly set, the attribute will be considered duplicable by default.
+
+The `duplicable` key should not be used for attributes that are extracted from block content using an [attribute source](#common-sources).
+
+_Example_: A `resourceId` attribute which should not be copied to duplicate blocks.
+
+```js
+{
+	resourceId: {
+		type: 'string',
+		duplicable: false
+	}
+}
+```
+
 ## Meta (deprecated)
 
 <div class="callout callout-alert">

packages/blocks/src/api/factory.js

@@ -115,7 +115,8 @@ export function __experimentalCloneSanitizedBlock(
 		{
 			...block.attributes,
 			...mergeAttributes,
-		}
+		},
+		{ shouldRemoveDuplicateAttributes: true }
 	);
 
 	return {

packages/blocks/src/api/test/factory.js

@@ -448,6 +448,34 @@ describe( 'block factory', () => {
 
 			expect( clonedBlock.attributes ).toEqual( {} );
 		} );
+
+		it( 'should not duplicate unique attributes, but fallback to available defaults', () => {
+			registerBlockType( 'core/test-block', {
+				...defaultBlockSettings,
+				attributes: {
+					nonDuplicableAttr: {
+						type: 'string',
+						duplicable: false,
+					},
+					nonDuplicableAttrWithDefault: {
+						type: 'string',
+						duplicable: false,
+						default: 'default-value',
+					},
+				},
+			} );
+
+			const block = createBlock( 'core/test-block', {
+				nonDuplicableAttr: 'unique-value',
+				nonDuplicableAttrWithDefault: 'unique-non-default-value',
+			} );
+
+			const clonedBlock = __experimentalCloneSanitizedBlock( block, {} );
+
+			expect( clonedBlock.attributes ).toEqual( {
+				nonDuplicableAttrWithDefault: 'default-value',
+			} );
+		} );
 	} );
 
 	describe( 'getPossibleBlockTransformations()', () => {

packages/blocks/src/api/test/utils.js

@@ -280,6 +280,59 @@ describe( 'sanitizeBlockAttributes', () => {
 		} );
 	} );
 
+	it( 'does not strip non-duplicable attributes by default', () => {
+		registerBlockType( 'core/test-block', {
+			attributes: {
+				nonDupicableAttr: {
+					type: 'string',
+					duplicable: false,
+				},
+			},
+			title: 'Test block',
+		} );
+
+		const attributes = __experimentalSanitizeBlockAttributes(
+			'core/test-block',
+			{
+				nonDupicableAttr: 'unique-value',
+			}
+		);
+
+		expect( attributes ).toEqual( {
+			nonDupicableAttr: 'unique-value',
+		} );
+	} );
+
+	it( 'removes non-duplicable attributes and falls back to defaults when shouleRemoveDuplicateAttributes is true', () => {
+		registerBlockType( 'core/test-block', {
+			attributes: {
+				nonDuplicableAttr: {
+					type: 'string',
+					duplicable: false,
+				},
+				nonDuplicableAttrWithDefault: {
+					type: 'string',
+					duplicable: false,
+					default: 'default-value',
+				},
+			},
+			title: 'Test block',
+		} );
+
+		const attributes = __experimentalSanitizeBlockAttributes(
+			'core/test-block',
+			{
+				nonDuplicableAttr: 'unique-value',
+				nonDuplicableAttrWithDefault: 'unique-non-default-value',
+			},
+			{ shouldRemoveDuplicateAttributes: true }
+		);
+
+		expect( attributes ).toEqual( {
+			nonDuplicableAttrWithDefault: 'default-value',
+		} );
+	} );
+
 	it( 'handles node and children sources as arrays', () => {
 		registerBlockType( 'core/test-block', {
 			attributes: {

packages/blocks/src/api/utils.js

@@ -237,11 +237,16 @@ export function getAccessibleBlockLabel(
  * Ensure attributes contains only values defined by block type, and merge
  * default values for missing attributes.
  *
- * @param {string} name       The block's name.
- * @param {Object} attributes The block's attributes.
+ * @param {string}  name                            The block's name.
+ * @param {Object}  attributes                      The block's attributes.
+ * @param {boolean} shouldRemoveDuplicateAttributes Whether to remove non-duplicable attributes.
  * @return {Object} The sanitized attributes.
  */
-export function __experimentalSanitizeBlockAttributes( name, attributes ) {
+export function __experimentalSanitizeBlockAttributes(
+	name,
+	attributes,
+	{ shouldRemoveDuplicateAttributes = false } = {}
+) {
 	// Get the type definition associated with a registered block.
 	const blockType = getBlockType( name );
 
@@ -255,7 +260,21 @@ export function __experimentalSanitizeBlockAttributes( name, attributes ) {
 			const value = attributes[ key ];
 
 			if ( undefined !== value ) {
-				accumulator[ key ] = value;
+				// Remove non-duplicable attributes and merge default values.
+				if ( shouldRemoveDuplicateAttributes ) {
+					// An attribute is duplicable by default if not specified in the schema.
+					const duplicable =
+						! schema.hasOwnProperty( 'duplicable' ) ||
+						schema.duplicable;
+
+					if ( duplicable ) {
+						accumulator[ key ] = value;
+					} else if ( schema.hasOwnProperty( 'default' ) ) {
+						accumulator[ key ] = schema.default;
+					}
+				} else {
+					accumulator[ key ] = value;
+				}
 			} else if ( schema.hasOwnProperty( 'default' ) ) {
 				accumulator[ key ] = schema.default;
 			}