REST API: Use wp_get_lastest_revision_id_and_total_count function i…

…n `WP_REST_Posts_Controller` class.

Add new function called `wp_get_lastest_revision_id_and_total_count`, that performs an optimized query to get the last revision and total and use it in `WP_REST_Posts_Controller` class. 

Props Spacedmonkey, timothyblynjacobs, furi3r, peterwilsoncc.
Fixes #55857.

git-svn-id: https://develop.svn.wordpress.org/trunk@53759 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -2024,17 +2024,16 @@ protected function prepare_links( $post ) {
 		}
 
 		if ( in_array( $post->post_type, array( 'post', 'page' ), true ) || post_type_supports( $post->post_type, 'revisions' ) ) {
-			$revisions       = wp_get_post_revisions( $post->ID, array( 'fields' => 'ids' ) );
-			$revisions_count = count( $revisions );
+			$revision        = wp_get_lastest_revision_id_and_total_count( $post->ID );
+			$revisions_count = ! is_wp_error( $revision ) ? $revision['count'] : 0;
 
 			$links['version-history'] = array(
 				'href'  => rest_url( trailingslashit( $base ) . $post->ID . '/revisions' ),
 				'count' => $revisions_count,
 			);
 
 			if ( $revisions_count > 0 ) {
-				$last_revision = array_shift( $revisions );
-
+				$last_revision                = $revision['revision'];
 				$links['predecessor-version'] = array(
 					'href' => rest_url( trailingslashit( $base ) . $post->ID . '/revisions/' . $last_revision ),
 					'id'   => $last_revision,

src/wp-includes/revision.php

@@ -527,6 +527,57 @@ function wp_get_post_revisions( $post = 0, $args = null ) {
 	return $revisions;
 }
 
+/**
+ * Get latest revision and count of revisions for a post.
+ *
+ * @since 6.1.0
+ *
+ * @param int|WP_Post|null $post Optional. Post ID or WP_Post object. Default is global $post.
+ * @return WP_Error|array {
+ *     Returns associative array with last revision and total count.
+ *
+ *     @type int $revision The last revision post id or 0 if non existing.
+ *     @type int $count The total count of revisions for $post_id.
+ * }
+ */
+function wp_get_lastest_revision_id_and_total_count( $post = null ) {
+	$post = get_post( $post );
+
+	if ( ! $post ) {
+		return new WP_Error( 'revision_error', __( 'Invalid post.' ) );
+	}
+
+	if ( ! wp_revisions_enabled( $post ) ) {
+		return new WP_Error( 'revision_error', __( 'Revisions not enabled.' ) );
+	}
+
+	$args = array(
+		'post_parent'         => $post->ID,
+		'fields'              => 'ids',
+		'post_type'           => 'revision',
+		'post_status'         => 'inherit',
+		'order'               => 'DESC',
+		'orderby'             => 'date ID',
+		'posts_per_page'      => 1,
+		'ignore_sticky_posts' => true,
+	);
+
+	$revision_query = new WP_Query();
+	$revisions      = $revision_query->query( $args );
+
+	if ( ! $revisions ) {
+		return array(
+			'revision' => 0,
+			'count'    => 0,
+		);
+	}
+
+	return array(
+		'revision' => $revisions[0],
+		'count'    => $revision_query->found_posts,
+	);
+}
+
 /**
  * Returns the url for viewing and potentially restoring revisions of a given post.
  *

tests/phpunit/tests/post/revisions.php

@@ -655,6 +655,57 @@ public function test_wp_save_post_revision_error() {
 		$this->assertWPError( $revision );
 	}
 
+	/**
+	 * Tests that wp_get_lastest_revision_id_and_total_count() returns last revision id and total count.
+	 *
+	 * @ticket 55857
+	 * @dataProvider data_wp_get_post_revisions_url
+	 */
+	public function test_wp_get_last_revision_id_and_total_count( $revisions ) {
+		$post_id = self::factory()->post->create();
+		for ( $i = 0; $i < $revisions; ++$i ) {
+			wp_update_post(
+				array(
+					'ID'         => $post_id,
+					'post_title' => 'Some Post',
+				)
+			);
+		}
+
+		$post_revisions     = wp_get_post_revisions( $post_id );
+		$last_post_revision = current( $post_revisions );
+		$revision           = wp_get_lastest_revision_id_and_total_count( $post_id );
+
+		$this->assertSame(
+			$last_post_revision->ID,
+			$revision['revision'],
+			'Failed asserting latest revision id.'
+		);
+
+		$this->assertSame(
+			count( $post_revisions ),
+			$revision['count'],
+			'Failed asserting total count of revision.'
+		);
+	}
+
+	/**
+	 * Tests that wp_get_lastest_revision_id_and_total_count() when no revisions.
+	 *
+	 * @ticket 55857
+	 */
+	public function test_wp_get_last_revision_id_and_total_count_no_revisions() {
+		$revision = wp_get_lastest_revision_id_and_total_count( null );
+		$this->assertWPError( $revision, 'Invalid Post, non existing revisions.' );
+		$this->assertSame( $revision->get_error_message(), 'Invalid post.' );
+
+		add_filter( 'wp_revisions_to_keep', '__return_zero' );
+		$post_id  = self::factory()->post->create();
+		$revision = wp_get_lastest_revision_id_and_total_count( $post_id );
+		$this->assertWPError( $revision, 'Revisions should be not enabled.' );
+		$this->assertSame( $revision->get_error_message(), 'Revisions not enabled.' );
+	}
+
 	/**
 	 * Tests that wp_get_post_revisions_url() returns the revisions URL.
 	 *

tests/phpunit/tests/rest-api/rest-posts-controller.php

@@ -121,7 +121,9 @@ public function wpSetUpBeforeRequest( $result, $server, $request ) {
 	}
 
 	public function save_posts_clauses( $orderby, $query ) {
-		array_push( $this->posts_clauses, $orderby );
+		if ( 'revision' !== $query->query_vars['post_type'] ) {
+			array_push( $this->posts_clauses, $orderby );
+		}
 		return $orderby;
 	}