Fix fatal error in Multi-Currency Compatibility (#4819)

* Fix fatal error by removing type hinting and returning early if expected type is not found.

* Add changelog.

changelog/fix-4818-multi-currency-compatibility-fatal

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Fix fatal error with call to MultiCurrency/Compatibility::convert_order_prices method.

includes/multi-currency/Compatibility.php

@@ -157,16 +157,16 @@ public function attach_order_modifier( $arg ) {
 	 *
 	 * @param WC_Order[]|WC_Order_Refund[] $results The results returned by the orders query.
 	 *
-	 * @return array
+	 * @return array|object of WC_Order objects
 	 */
-	public function convert_order_prices( $results ): array {
+	public function convert_order_prices( $results ) {
 		$backtrace_calls = [
 			'Automattic\WooCommerce\Admin\Notes\NewSalesRecord::sum_sales_for_date',
 			'Automattic\WooCommerce\Admin\Notes\NewSalesRecord::possibly_add_note',
 		];
 
-		// If the call we're expecting isn't in the backtrace, then just do nothing and return the results.
-		if ( ! $this->utils->is_call_in_backtrace( $backtrace_calls ) ) {
+		// If the results are not an array, or if the call we're expecting isn't in the backtrace, then just do nothing and return the results.
+		if ( ! is_array( $results ) || ! $this->utils->is_call_in_backtrace( $backtrace_calls ) ) {
 			return $results;
 		}
 

tests/unit/multi-currency/test-class-compatibility.php

@@ -190,4 +190,15 @@ public function test_filter_woocommerce_order_query() {
 		$order = wc_get_order( $result->get_id() );
 		$this->assertEquals( 1000, $order->get_total() );
 	}
+
+	public function test_filter_woocommerce_order_query_with_object_not_array() {
+		$order = wc_create_order();
+		$order->set_total( 1000 );
+		$order->set_currency( 'GBP' );
+
+		// Turn the order array into an object to confirm the object is returned as is.
+		$expected = (object) [ $order ];
+
+		$this->assertEquals( $expected, $this->compatibility->convert_order_prices( $expected, [] ) );
+	}
 }