Footnotes: disable for synced patterns and prevent duplication for pa…

…ges in site editor (#53003)

* Initial commit:
- Prevent footnote creation withing core/block
- Only insert a footnote if one isn't found in the entity block list

* Try grabbing controlled blocks from parent post content block

* Cache `selectedClientId`
Get hasParentCoreBlocks using separate useSelect call.

* Rename hasParentCoreBlocks to isBlockWithinPattern
Add comments

* Removing while loop since we're already fetching the post content parent in the `getBlockParentsByBlockName` call above

* Reinstating while loop because it can deal with nested blocks

---------

Co-authored-by: Andrew Serong <14988353+andrewserong@users.noreply.github.com>

packages/block-library/src/footnotes/format.js

@@ -26,6 +26,10 @@ import { unlock } from '../lock-unlock';
 const { usesContextKey } = unlock( privateApis );
 
 export const formatName = 'core/footnote';
+
+const POST_CONTENT_BLOCK_NAME = 'core/post-content';
+const SYNCED_PATTERN_BLOCK_NAME = 'core/block';
+
 export const format = {
 	title: __( 'Footnote' ),
 	tagName: 'sup',
@@ -44,13 +48,30 @@ export const format = {
 		const registry = useRegistry();
 		const {
 			getSelectedBlockClientId,
+			getBlocks,
 			getBlockRootClientId,
 			getBlockName,
-			getBlocks,
+			getBlockParentsByBlockName,
 		} = useSelect( blockEditorStore );
 		const footnotesBlockType = useSelect( ( select ) =>
 			select( blocksStore ).getBlockType( name )
 		);
+		/*
+		 * This useSelect exists because we need to use its return value
+		 * outside the event callback.
+		 */
+		const isBlockWithinPattern = useSelect( ( select ) => {
+			const {
+				getBlockParentsByBlockName: _getBlockParentsByBlockName,
+				getSelectedBlockClientId: _getSelectedBlockClientId,
+			} = select( blockEditorStore );
+			const parentCoreBlocks = _getBlockParentsByBlockName(
+				_getSelectedBlockClientId(),
+				SYNCED_PATTERN_BLOCK_NAME
+			);
+			return parentCoreBlocks && parentCoreBlocks.length > 0;
+		}, [] );
+
 		const { selectionChange, insertBlock } =
 			useDispatch( blockEditorStore );
 
@@ -62,6 +83,11 @@ export const format = {
 			return null;
 		}
 
+		// Checks if the selected block lives within a pattern.
+		if ( isBlockWithinPattern ) {
+			return null;
+		}
+
 		function onClick() {
 			registry.batch( () => {
 				let id;
@@ -86,10 +112,27 @@ export const format = {
 					onChange( newValue );
 				}
 
+				const selectedClientId = getSelectedBlockClientId();
+
+				/*
+				 * Attempts to find a common parent post content block.
+				 * This allows for locating blocks within a page edited in the site editor.
+				 */
+				const parentPostContent = getBlockParentsByBlockName(
+					selectedClientId,
+					POST_CONTENT_BLOCK_NAME
+				);
+
+				// When called with a post content block, getBlocks will return
+				// the block with controlled inner blocks included.
+				const blocks = parentPostContent.length
+					? getBlocks( parentPostContent[ 0 ] )
+					: getBlocks();
+
 				// BFS search to find the first footnote block.
 				let fnBlock = null;
 				{
-					const queue = [ ...getBlocks() ];
+					const queue = [ ...blocks ];
 					while ( queue.length ) {
 						const block = queue.shift();
 						if ( block.name === name ) {
@@ -104,12 +147,11 @@ export const format = {
 				// When there is no footnotes block in the post, create one and
 				// insert it at the bottom.
 				if ( ! fnBlock ) {
-					const clientId = getSelectedBlockClientId();
-					let rootClientId = getBlockRootClientId( clientId );
+					let rootClientId = getBlockRootClientId( selectedClientId );
 
 					while (
 						rootClientId &&
-						getBlockName( rootClientId ) !== 'core/post-content'
+						getBlockName( rootClientId ) !== POST_CONTENT_BLOCK_NAME
 					) {
 						rootClientId = getBlockRootClientId( rootClientId );
 					}