Update block_template_part to expand shortcodes in template parts

Add set of typical actions run on `the_content` to the `block_template_part` function.
This replicate the behavior of the template part block's render method.

src/wp-includes/block-template-utils.php

@@ -1200,7 +1200,20 @@ function block_template_part( $part ) {
 	if ( ! $template_part || empty( $template_part->content ) ) {
 		return;
 	}
-	echo do_blocks( $template_part->content );
+
+	// Run through the actions that are typically taken on the_content.
+	$content = do_blocks( $template_part->content );
+	$content = wptexturize( $content );
+	$content = convert_smilies( $content );
+	$content = shortcode_unautop( $content );
+	$content = wp_filter_content_tags( $content );
+	$content = do_shortcode( $content );
+
+	// Handle embeds for block template parts.
+	global $wp_embed;
+	$content = $wp_embed->autoembed( $content );
+
+	echo $content;
 }
 
 /**

tests/phpunit/data/themedir1/block-theme/parts/template-part-shortcode.html

@@ -0,0 +1,7 @@
+<!-- wp:group {"tagName":"header","layout":{"type":"flex","flexWrap":"wrap"}} -->
+<header id="masthead" class="wp-block-group">
+	<!-- wp:shortcode -->
+	[test_shortcode]
+	<!-- /wp:shortcode -->
+</header>
+<!--  /wp:group -->

tests/phpunit/tests/block-template-utils.php

@@ -10,6 +10,8 @@ class Tests_Block_Template_Utils extends WP_UnitTestCase {
 
 	const TEST_THEME = 'block-theme';
 
+	const TEST_SHORTCODE = 'test_shortcode';
+
 	private static $template_post;
 	private static $template_part_post;
 
@@ -340,4 +342,26 @@ public function test_wp_generate_block_templates_export_file() {
 		}
 		$this->assertTrue( $has_html_files, 'contains at least one html file' );
 	}
+
+	/**
+	 * Should expand shortcodes in block template part.
+	 *
+	 * @ticket 56780
+	 * @covers ::block_template_part
+	 */
+	public function test_block_template_part_render_shortcode() {
+		add_shortcode( self::TEST_SHORTCODE, array( $this, 'render_test_shortcode' ) );
+
+		ob_start();
+		block_template_part( 'template-part-shortcode' );
+		$generated_content = ob_get_clean();
+
+		remove_shortcode( self::TEST_SHORTCODE );
+
+		$this->assertStringContainsString( 'test_shortcode_rendered', $generated_content );
+	}
+
+	public function render_test_shortcode() {
+		return 'test_shortcode_rendered';
+	}
 }