Make CustomerExpandableField inherit ExpandableObjectField

Author: yurii-prykhodko-solid

lib/src/expanded/subscription_expanded.dart

@@ -23,23 +23,19 @@ class SubscriptionExpanded {
   ) {
     List<Discount>? discounts;
     if (expand.contains(SubscriptionExpandableField.discounts)) {
-      discounts = DiscountsExpandableField().extract(json);
+      discounts = const DiscountsExpandableField().extract(json);
     }
 
     InvoiceExpanded? latestInvoice;
     if (expand.contains(SubscriptionExpandableField.latestInvoice)) {
-      latestInvoice = LatestInvoiceExpandedExpandableField(
+      latestInvoice = const LatestInvoiceExpandedExpandableField(
         expand: {InvoiceExpandableField.paymentIntent},
       ).extract(json);
     }
 
     Customer? customer;
     if (expand.contains(SubscriptionExpandableField.customer)) {
-      const customerExpander = CustomerExpandableField();
-      customer = customerExpander.extract(json);
-
-      /// A shim so that Subscription gets parsed correctly
-      json[customerExpander.field] = customer.id;
+      customer = const CustomerExpandableField().extract(json);
     }
 
     return SubscriptionExpanded(

lib/src/utils/expandable_fields/customer_expandable_field.dart

@@ -1,12 +1,16 @@
 import 'package:stripe/messages.dart';
-import 'package:stripe/src/utils/expandable_field.dart';
+import 'package:stripe/src/utils/expandable_object_field.dart';
 
-class CustomerExpandableField extends ExpandableField<Customer> {
+class CustomerExpandableField extends ExpandableObjectField<Customer> {
   @override
   String get field => 'customer';
 
   const CustomerExpandableField();
 
   @override
-  Customer extract(Map<String, dynamic> json) => Customer.fromJson(json[field]);
+  Customer parse(Map<String, dynamic> object) =>
+      Customer.fromJson(object[field]);
+
+  @override
+  String replacement(Customer parsedValue) => parsedValue.id;
 }