diff -r c7c34916027a -r 177826044cd9 wp/wp-includes/blocks/tag-cloud.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/blocks/tag-cloud.php	Mon Oct 14 18:28:13 2019 +0200
@@ -0,0 +1,71 @@
+<?php
+/**
+ * Server-side rendering of the `core/tag-cloud` block.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Renders the `core/tag-cloud` block on server.
+ *
+ * @param array $attributes The block attributes.
+ *
+ * @return string Returns the tag cloud for selected taxonomy.
+ */
+function render_block_core_tag_cloud( $attributes ) {
+	$class = isset( $attributes['align'] ) ?
+		"wp-block-tag-cloud align{$attributes['align']}" :
+		'wp-block-tag-cloud';
+
+	if ( isset( $attributes['className'] ) ) {
+		$class .= ' ' . $attributes['className'];
+	}
+
+	$args = array(
+		'echo'       => false,
+		'taxonomy'   => $attributes['taxonomy'],
+		'show_count' => $attributes['showTagCounts'],
+	);
+
+	$tag_cloud = wp_tag_cloud( $args );
+
+	if ( ! $tag_cloud ) {
+		$tag_cloud = esc_html( __( 'No terms to show.' ) );
+	}
+
+	return sprintf(
+		'<p class="%1$s">%2$s</p>',
+		esc_attr( $class ),
+		$tag_cloud
+	);
+}
+
+/**
+ * Registers the `core/tag-cloud` block on server.
+ */
+function register_block_core_tag_cloud() {
+	register_block_type(
+		'core/tag-cloud',
+		array(
+			'attributes'      => array(
+				'taxonomy'      => array(
+					'type'    => 'string',
+					'default' => 'post_tag',
+				),
+				'className'     => array(
+					'type' => 'string',
+				),
+				'showTagCounts' => array(
+					'type'    => 'boolean',
+					'default' => false,
+				),
+				'align'         => array(
+					'type' => 'string',
+				),
+			),
+			'render_callback' => 'render_block_core_tag_cloud',
+		)
+	);
+}
+
+add_action( 'init', 'register_block_core_tag_cloud' );