Media: Optionally return attachment id from `media_sideload_image()`.

Introduces option to `$return` parameter to return the attachment id created after a successful image sideload.

Props slbmeh, kawauso, alexkingorg, SergeyBiryukov, georgestephanis, DrewAPicture, nacin, trepmal, mattheu, kraftbj, whyisjake, dotancohen, MrGregWaugh, danielbachhuber.
Fixes #19629.
Built from https://develop.svn.wordpress.org/trunk@40597


git-svn-id: http://core.svn.wordpress.org/trunk@40467 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/media.php

@@ -852,11 +852,12 @@ function wp_media_upload_handler() {
  *
  * @since 2.6.0
  * @since 4.2.0 Introduced the `$return` parameter.
+ * @since 4.8.0 Introduced the 'id' option within the `$return` parameter.
  *
  * @param string $file    The URL of the image to download.
  * @param int    $post_id The post ID the media is to be associated with.
  * @param string $desc    Optional. Description of the image.
- * @param string $return  Optional. Accepts 'html' (image tag html) or 'src' (URL). Default 'html'.
+ * @param string $return  Optional. Accepts 'html' (image tag html) or 'src' (URL), or 'id' (attachment ID). Default 'html'.
  * @return string|WP_Error Populated HTML img tag on success, WP_Error object otherwise.
  */
 function media_sideload_image( $file, $post_id, $desc = null, $return = 'html' ) {
@@ -886,6 +887,9 @@ function media_sideload_image( $file, $post_id, $desc = null, $return = 'html' )
 		if ( is_wp_error( $id ) ) {
 			@unlink( $file_array['tmp_name'] );
 			return $id;
+		// If attachment id was requested, return it early.
+		} elseif ( $return === 'id' ) {
+			return $id;
 		}
 
 		$src = wp_get_attachment_url( $id );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-alpha-40596';
+$wp_version = '4.8-alpha-40597';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.