REST API: Include `block_version` on Post `content` object.

The `block_version` denotes which version of Blocks the `post_content` contains. Introduces new `block_version()` function for versioning Blocks.

Merges [43770] from the 5.0 branch to trunk.

Props danielbachhuber, birgire.
Fixes #43887.

Built from https://develop.svn.wordpress.org/trunk@44127


git-svn-id: http://core.svn.wordpress.org/trunk@43957 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/blocks.php

@@ -262,3 +262,17 @@ function _recurse_do_blocks( $blocks, $all_blocks ) {
 
 	return $rendered_content;
 }
+
+/**
+ * Returns the current version of the block format that the content string is using.
+ *
+ * If the string doesn't contain blocks, it returns 0.
+ *
+ * @since 5.0.0
+ *
+ * @param string $content Content to test.
+ * @return int The block format version.
+ */
+function block_version( $content ) {
+	return has_blocks( $content ) ? 1 : 0;
+}

wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -1525,6 +1525,7 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 				/** This filter is documented in wp-includes/post-template.php */
 				'rendered'      => post_password_required( $post ) ? '' : apply_filters( 'the_content', $post->post_content ),
 				'protected'     => (bool) $post->post_password,
+				'block_version' => block_version( $post->post_content ),
 			);
 		}
 
@@ -2073,6 +2074,12 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 								'context'     => array( 'view', 'edit' ),
 								'readonly'    => true,
 							),
+							'block_version' => array(
+								'description' => __( 'Version of the content block format used by the object.' ),
+								'type'        => 'integer',
+								'context'     => array( 'edit' ),
+								'readonly'    => true,
+							),
 							'protected'     => array(
 								'description' => __( 'Whether the content is protected with a password.' ),
 								'type'        => 'boolean',

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44126';
+$wp_version = '5.1-alpha-44127';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.