If stock changes between page load and editing, reject stock changes

Fixes #15818

includes/admin/meta-boxes/class-wc-meta-box-product-data.php

@@ -310,6 +310,17 @@ class WC_Meta_Box_Product_Data {
 		$classname    = WC_Product_Factory::get_product_classname( $post_id, $product_type ? $product_type : 'simple' );
 		$product      = new $classname( $post_id );
 		$attributes   = self::prepare_attributes();
+		$stock        = null;
+
+		// Handle stock changes.
+		if ( isset( $_POST['_stock'] ) ) {
+			if ( isset( $_POST['_original_stock'] ) && wc_stock_amount( $product->get_stock_quantity( 'edit' ) ) !== wc_stock_amount( $_POST['_original_stock'] ) ) {
+				WC_Admin_Meta_Boxes::add_error( sprintf( __( 'The stock has not been updated because the value has changed since editing. Product %d has %d units in stock.', 'woocommerce' ), $product->get_id(), $product->get_stock_quantity( 'edit' ) ) );
+			} else {
+				$stock = wc_stock_amount( $_POST['_stock'] );
+			}
+		}
+
 		$errors       = $product->set_props( array(
 			'sku'                => isset( $_POST['_sku'] ) ? wc_clean( $_POST['_sku'] ) : null,
 			'purchase_note'      => wp_kses_post( stripslashes( $_POST['_purchase_note'] ) ),
@@ -334,7 +345,7 @@ class WC_Meta_Box_Product_Data {
 			'manage_stock'       => ! empty( $_POST['_manage_stock'] ),
 			'backorders'         => isset( $_POST['_backorders'] ) ? wc_clean( $_POST['_backorders'] ) : null,
 			'stock_status'       => wc_clean( $_POST['_stock_status'] ),
-			'stock_quantity'     => isset( $_POST['_stock'] ) ? wc_stock_amount( $_POST['_stock'] ) : null,
+			'stock_quantity'     => $stock,
 			'download_limit'     => '' === $_POST['_download_limit'] ? '' : absint( $_POST['_download_limit'] ),
 			'download_expiry'    => '' === $_POST['_download_expiry'] ? '' : absint( $_POST['_download_expiry'] ),
 			'downloads'          => self::prepare_downloads(
@@ -391,6 +402,17 @@ class WC_Meta_Box_Product_Data {
 				}
 				$variation_id = absint( $_POST['variable_post_id'][ $i ] );
 				$variation    = new WC_Product_Variation( $variation_id );
+				$stock        = null;
+
+				// Handle stock changes.
+				if ( isset( $_POST['variable_stock'], $_POST['variable_stock'][ $i ] ) ) {
+					if ( isset( $_POST['variable_original_stock'], $_POST['variable_original_stock'][ $i ] ) && wc_stock_amount( $variation->get_stock_quantity( 'edit' ) ) !== wc_stock_amount( $_POST['variable_original_stock'][ $i ] ) ) {
+						WC_Admin_Meta_Boxes::add_error( sprintf( __( 'The stock has not been updated because the value has changed since editing. Product %d has %d units in stock.', 'woocommerce' ), $variation->get_id(), $variation->get_stock_quantity( 'edit' ) ) );
+					} else {
+						$stock = wc_stock_amount( $_POST['variable_stock'][ $i ] );
+					}
+				}
+
 				$errors       = $variation->set_props( array(
 					'status'            => isset( $_POST['variable_enabled'][ $i ] ) ? 'publish' : 'private',
 					'menu_order'        => wc_clean( $_POST['variation_menu_order'][ $i ] ),
@@ -409,7 +431,7 @@ class WC_Meta_Box_Product_Data {
 						isset( $_POST['_wc_variation_file_hashes'][ $variation_id ] ) ? $_POST['_wc_variation_file_hashes'][ $variation_id ] : array()
 					),
 					'manage_stock'      => isset( $_POST['variable_manage_stock'][ $i ] ),
-					'stock_quantity'    => isset( $_POST['variable_stock'], $_POST['variable_stock'][ $i ] ) ? wc_clean( $_POST['variable_stock'][ $i ] ) : null,
+					'stock_quantity'    => $stock,
 					'backorders'        => isset( $_POST['variable_backorders'], $_POST['variable_backorders'][ $i ] ) ? wc_clean( $_POST['variable_backorders'][ $i ] ) : null,
 					'stock_status'      => wc_clean( $_POST['variable_stock_status'][ $i ] ),
 					'image_id'          => wc_clean( $_POST['upload_image_id'][ $i ] ),

includes/admin/meta-boxes/views/html-product-data-inventory.php

@@ -35,7 +35,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 
 				woocommerce_wp_text_input( array(
 					'id'                => '_stock',
-					'value'             => $product_object->get_stock_quantity( 'edit' ),
+					'value'             => wc_stock_amount( $product_object->get_stock_quantity( 'edit' ) ),
 					'label'             => __( 'Stock quantity', 'woocommerce' ),
 					'desc_tip'          => true,
 					'description'       => __( 'Stock quantity. If this is a variable product this value will be used to control stock for all variations, unless you define stock at variation level.', 'woocommerce' ),
@@ -46,6 +46,8 @@ if ( ! defined( 'ABSPATH' ) ) {
 					'data_type'         => 'stock',
 				) );
 
+				echo '<input type="hidden" name="_original_stock" value="' . esc_attr( wc_stock_amount( $product_object->get_stock_quantity( 'edit' ) ) ) . '" />';
+
 				woocommerce_wp_select( array(
 					'id'          => '_backorders',
 					'value'       => $product_object->get_backorders( 'edit' ),

includes/admin/meta-boxes/views/html-variation-admin.php

@@ -158,7 +158,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 						woocommerce_wp_text_input( array(
 							'id'                => "variable_stock{$loop}",
 							'name'              => "variable_stock[{$loop}]",
-							'value'             => $variation_object->get_stock_quantity( 'edit' ),
+							'value'             => wc_stock_amount( $variation_object->get_stock_quantity( 'edit' ) ),
 							'label'             => __( 'Stock quantity', 'woocommerce' ),
 							'desc_tip'          => true,
 							'description'       => __( "Enter a quantity to enable stock management at variation level, or leave blank to use the parent product's options.", 'woocommerce' ),
@@ -170,6 +170,8 @@ if ( ! defined( 'ABSPATH' ) ) {
 							'wrapper_class'     => 'form-row form-row-first',
 						) );
 
+						echo '<input type="hidden" name="variable_original_stock[' . $loop . ']" value="' . esc_attr( wc_stock_amount( $variation_object->get_stock_quantity( 'edit'  ) ) ) . '" />';
+
 						woocommerce_wp_select( array(
 							'id'            => "variable_backorders{$loop}",
 							'name'          => "variable_backorders[{$loop}]",