Block Bindings: Fix back-compat layer

backport-changelog/6.9/9469.md

@@ -1,3 +1,4 @@
 https://github.com/WordPress/wordpress-develop/pull/9469
 
 * https://github.com/WordPress/gutenberg/pull/71389
+* https://github.com/WordPress/gutenberg/pull/71691

lib/compat/wordpress-6.9/block-bindings.php

@@ -36,26 +36,39 @@ function gutenberg_block_bindings_render_block( $block_content, $block, $instanc
 		return $block_content;
 	}
 
-	$attributes = $instance->parsed_block['attrs'];
 	// Process the block bindings and get attributes updated with the values from the sources.
 	$computed_attributes = gutenberg_process_block_bindings( $instance );
 	if ( empty( $computed_attributes ) ) {
 		return $block_content;
 	}
 
-	// Merge the computed attributes with the original attributes.
-	$instance->attributes = array_merge( $attributes, $computed_attributes );
+	/*
+	 * Merge the computed attributes with the original attributes.
+	 *
+	 * Note that this is not a recursive merge, meaning that nested attributes --
+	 * such as block bindings metadata -- will be completely replaced.
+	 * This is desirable. At this point, Core has already processed any block
+	 * bindings that it supports. What remains to be processed are only the attributes
+	 * for which support was added later (through the `block_bindings_supported_attributes`
+	 * filter). To do so, we'll run `$instance->render()` once more
+	 * so the block can update its content based on those attributes.
+	 */
+	$instance->attributes = array_merge( $instance->attributes, $computed_attributes );
+
+	/*
+	 * If we're dealing with the Button block, we remove the bindings metadata
+	 * in order to avoid having it reprocessed, which would lead to Core
+	 * capitalizing the wrapper tag (e.g. <DIV>).
+	 */
+	if ( 'core/button' === $instance->name ) {
+		unset( $instance->parsed_block['attrs']['metadata']['bindings'] );
+	}
 
 	/**
-	 * This filter is called from WP_Block::render(), after the block content has
-	 * already been rendered. However, dynamic blocks expect their render() method
-	 * to receive block attributes to have their bound values. This means that we have
-	 * to re-render the block here.
-	 * To do so, we'll set a flag that this filter checks when invoked to avoid infinite
-	 * recursion. Furthermore, we can unset all of the block's bindings, as we know that
-	 * they have been processed by the time we reach this point.
+	 * This filter (`gutenberg_block_bindings_render_block`) is called from `WP_Block::render()`.
+	 * To avoid infinite recursion, we set a flag that this filter checks when invoked which tells
+	 * it to exit early.
 	 */
-	unset( $instance->parsed_block['attrs']['metadata']['bindings'] );
 	$inside_block_bindings_render = true;
 	$block_content                = $instance->render();
 	$inside_block_bindings_render = false;

phpunit/block-bindings-test.php

@@ -45,6 +45,14 @@ function ( $supported_attributes ) {
 				return $supported_attributes;
 			}
 		);
+
+		add_filter(
+			'block_bindings_supported_attributes_core/image',
+			function ( $supported_attributes ) {
+				$supported_attributes[] = 'caption';
+				return $supported_attributes;
+			}
+		);
 	}
 
 	/**
@@ -259,11 +267,19 @@ public function test_passing_uses_context_to_source() {
 	 * Tests if the block content is updated with the value returned by the source
 	 * for the Image block in the placeholder state.
 	 *
+	 * Furthermore tests if the caption attribute, for which support is added via the
+	 * `block_bindings_supported_attributes_core/image` filter, is correctly processed.
+	 *
 	 * @covers ::register_block_bindings_source
 	 */
 	public function test_update_block_with_value_from_source_image_placeholder() {
-		$get_value_callback = function () {
-			return 'https://example.com/image.jpg';
+		$get_value_callback = function ( $source_args, $block_instance, $attribute_name ) {
+			if ( 'url' === $attribute_name ) {
+				return 'https://example.com/image.jpg';
+			}
+			if ( 'caption' === $attribute_name ) {
+				return 'Example Image';
+			}
 		};
 
 		register_block_bindings_source(
@@ -275,8 +291,8 @@ public function test_update_block_with_value_from_source_image_placeholder() {
 		);
 
 		$block_content = <<<HTML
-<!-- wp:image {"metadata":{"bindings":{"url":{"source":"test/source"}}}} -->
-<figure class="wp-block-image"><img alt=""/></figure>
+<!-- wp:image {"metadata":{"bindings":{"url":{"source":"test/source"},"caption":{"source":"test/source"}}}} -->
+<figure class="wp-block-image"><img alt=""/><figcaption class="wp-element-caption"></figcaption></figure>
 <!-- /wp:image -->
 HTML;
 		$parsed_blocks = parse_blocks( $block_content );
@@ -289,7 +305,12 @@ public function test_update_block_with_value_from_source_image_placeholder() {
 			"The 'url' attribute should be updated with the value returned by the source."
 		);
 		$this->assertSame(
-			'<figure class="wp-block-image"><img src="https://example.com/image.jpg" alt=""/></figure>',
+			'Example Image',
+			$block->attributes['caption'],
+			"The 'caption' attribute should be updated with the value returned by the source."
+		);
+		$this->assertSame(
+			'<figure class="wp-block-image"><img src="https://example.com/image.jpg" alt=""/><figcaption class="wp-element-caption">Example Image</figcaption></figure>',
 			trim( $result ),
 			'The block content should be updated with the value returned by the source.'
 		);