feat: add support for resolving Template Part blocks

.changeset/silver-cups-explode.md

@@ -0,0 +1,5 @@
+---
+"@wpengine/wp-graphql-content-blocks": minor
+---
+
+feat: add support for resolving Template Part blocks

includes/Data/ContentBlocksResolver.php

@@ -148,7 +148,7 @@ private static function handle_do_block( array $block ): ?array {
 		$block['clientId'] = uniqid();
 
 		// @todo apply more hydrations.
-
+		$block = self::populate_template_part_inner_blocks( $block );
 		$block = self::populate_reusable_blocks( $block );
 
 		$block = self::populate_pattern_inner_blocks( $block );
@@ -183,6 +183,36 @@ private static function is_block_empty( array $block ): bool {
 		return empty( trim( $stripped ?? '' ) );
 	}
 
+	/**
+	 * Populates the innerBlocks of a template part block with the blocks from the template part.
+	 *
+	 * @param array<string,mixed> $block The block to populate.
+	 *
+	 * @return array<string,mixed> The populated block.
+	 */
+	private static function populate_template_part_inner_blocks( array $block ): array {
+		// Bail if not WP 5.8 or later.
+		if ( ! function_exists( 'get_block_templates' ) ) {
+			return $block;
+		}
+
+		if ( 'core/template-part' !== $block['blockName'] || ! isset( $block['attrs']['slug'] ) ) {
+			return $block;
+		}
+
+		$matching_templates = get_block_templates( [ 'slug__in' => [ $block['attrs']['slug'] ] ], 'wp_template_part' );
+
+		$template_blocks = ! empty( $matching_templates[0]->content ) ? self::parse_blocks( $matching_templates[0]->content ) : null;
+
+		if ( empty( $template_blocks ) ) {
+			return $block;
+		}
+
+		$block['innerBlocks'] = $template_blocks;
+
+		return $block;
+	}
+
 	/**
 	 * Populates reusable blocks with the blocks from the reusable ref ID.
 	 *

tests/unit/ContentBlocksResolverTest.php

@@ -413,4 +413,58 @@ public function test_resolve_content_blocks_resolves_pattern_inner_blocks() {
 		// Cleanup: Unregistering the pattern.
 		unregister_block_pattern( $pattern_name );
 	}
+
+	/**
+	 * Tests that template part inner blocks are resolved correctly.
+	 */
+	public function test_resolve_content_blocks_resolves_template_part_inner_blocks() {
+		// Skip if template part functionality is not supported
+		if ( ! function_exists( 'get_block_templates' ) ) {
+			$this->markTestSkipped( 'Template part functionality not supported in this WordPress version.' );
+		}
+
+		// Mock the get_block_templates function to control the output.
+		$mock_template = (object) [
+			'content' => '<!-- wp:paragraph /--><!-- wp:heading /-->',
+		];
+
+		add_filter(
+			'get_block_templates',
+			function () use ( $mock_template ) {
+				return [ $mock_template ];
+			}
+		);
+
+		// Update post content to include template part block
+		$post_content = '
+			<!-- wp:template-part {"slug":"test-template-part"} /-->
+		';
+
+		wp_update_post(
+			[
+				'ID'           => $this->post_id,
+				'post_content' => $post_content,
+			]
+		);
+
+		$post_model = new Post( get_post( $this->post_id ) );
+
+		// Resolve blocks as nested
+		$resolved_blocks = $this->instance->resolve_content_blocks( $post_model, [ 'flat' => false ] );
+
+		// Assertions
+		$this->assertCount( 1, $resolved_blocks, 'There should be only one top-level block (template-part).' );
+		$this->assertEquals( 'core/template-part', $resolved_blocks[0]['blockName'] );
+		$this->assertCount( 2, $resolved_blocks[0]['innerBlocks'], 'There should be two inner blocks in the template part.' );
+		$this->assertEquals( 'core/paragraph', $resolved_blocks[0]['innerBlocks'][0]['blockName'] );
+		$this->assertEquals( 'core/heading', $resolved_blocks[0]['innerBlocks'][1]['blockName'] );
+
+		// Resolve blocks as flat
+		$resolved_flat_blocks = $this->instance->resolve_content_blocks( $post_model, [ 'flat' => true ] );
+
+		$this->assertCount( 3, $resolved_flat_blocks, 'There should be three blocks when flattened.' );
+		$this->assertEquals( 'core/template-part', $resolved_flat_blocks[0]['blockName'] );
+		$this->assertEquals( 'core/paragraph', $resolved_flat_blocks[1]['blockName'] );
+		$this->assertEquals( 'core/heading', $resolved_flat_blocks[2]['blockName'] );
+	}
 }