From 879bde0401e0152fdbf6089cdfd92856eb3cd6e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fabian=20Ka=CC=88gy?= <mail@fabian-kaegy.de>
Date: Tue, 19 Oct 2021 13:19:23 +0200
Subject: [PATCH 1/2] add new filter called `blocks.cloneBlock` to modify
 behavior of cloning

---
 packages/blocks/src/api/factory.js | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/packages/blocks/src/api/factory.js b/packages/blocks/src/api/factory.js
index 4abd12a802f03f..83a23ac47986be 100644
--- a/packages/blocks/src/api/factory.js
+++ b/packages/blocks/src/api/factory.js
@@ -118,7 +118,14 @@ export function __experimentalCloneSanitizedBlock(
 		}
 	);
 
-	return {
+	/**
+	 * Filters the cloned block.
+	 * The entire new block object is passed and can be modified
+	 *
+	 * @param {string} blockType block type of the block being transformed.
+	 * @param {Object} block     cloned block object
+	 */
+	return applyFilters( 'blocks.cloneBlock', block.name, {
 		...block,
 		clientId,
 		attributes: sanitizedAttributes,
@@ -127,7 +134,7 @@ export function __experimentalCloneSanitizedBlock(
 			block.innerBlocks.map( ( innerBlock ) =>
 				__experimentalCloneSanitizedBlock( innerBlock )
 			),
-	};
+	} );
 }
 
 /**

From 25c3fb2c53f2d4f11d799cfa059242a6daa7b4d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fabian=20Ka=CC=88gy?= <mail@fabian-kaegy.de>
Date: Tue, 19 Oct 2021 13:21:40 +0200
Subject: [PATCH 2/2] use `blocks.cloneBlock` hook to make sure the anchor
 stays unique

---
 packages/block-editor/src/hooks/anchor.js | 41 +++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/packages/block-editor/src/hooks/anchor.js b/packages/block-editor/src/hooks/anchor.js
index bed166dceb8807..dc8e1396879d1b 100644
--- a/packages/block-editor/src/hooks/anchor.js
+++ b/packages/block-editor/src/hooks/anchor.js
@@ -153,7 +153,48 @@ export function addSaveProps( extraProps, blockType, attributes ) {
 	return extraProps;
 }
 
+/**
+ * Make sure the anchor continues to stay unique when the block is cloned
+ *
+ * @param {string} blockType type of the block
+ * @param {Object} block     cloned block object
+ * @return {Object} modified cloned block object
+ */
+export function cloneAttribute( blockType, block ) {
+	if (
+		hasBlockSupport( blockType, 'anchor' ) &&
+		has( block, 'attributes.anchor' )
+	) {
+		// check wether the anchor already ends with a `-${number}`
+		const index = block.attributes.anchor.lastIndexOf( '-' );
+		const result = block.attributes.anchor.substring( index + 1 );
+
+		// store the anchor without the `-${number}`
+		const shortendAnchor =
+			index > 0
+				? block.attributes.anchor.substring( 0, index )
+				: block.attributes.anchor;
+
+		// generate the suffix number
+		let suffix = 1;
+		if ( result ) {
+			const number = parseInt( result );
+
+			if ( number ) {
+				suffix = number + 1;
+			}
+		}
+
+		// add the suffix to the anchor
+		block.attributes.anchor = `${ shortendAnchor }-${ suffix }`;
+	}
+
+	// return the modified cloned block
+	return block;
+}
+
 addFilter( 'blocks.registerBlockType', 'core/anchor/attribute', addAttribute );
+addFilter( 'blocks.cloneBlock', 'core/anchor/clone', cloneAttribute );
 addFilter(
 	'editor.BlockEdit',
 	'core/editor/anchor/with-inspector-control',