Fix formatting and analysis warnings

packages/in_app_purchase/in_app_purchase_platform_interface/lib/in_app_purchase_platform_interface.dart

@@ -2,5 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+export 'src/errors/errors.dart';
 export 'src/in_app_purchase_platform.dart';
 export 'src/types/types.dart';

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/errors/errors.dart

@@ -0,0 +1 @@
+export 'purchase_exception.dart';

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/errors/purchase_exception.dart

@@ -1,9 +1,11 @@
-import 'package:flutter/services.dart';
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
 
 /// Thrown to indicate that a purchase could not be finished successfully.
-/// 
+///
 /// The exception should be implemented per platform. Each platform implementation
-/// should override the [shouldRetry] property and return the correct value 
+/// should override the [shouldRetry] property and return the correct value
 /// according to the platform specific error codes.
 abstract class PurchaseException implements Exception {
   /// Creates a [PurchaseException] with the specified error [code] and optional
@@ -13,15 +15,15 @@ abstract class PurchaseException implements Exception {
     this.message,
   });
 
-  /// The error code indicating 
+  /// The error code indicating
   final String code;
 
   /// An human readible error message, possibly null.
   final String? message;
 
   /// Indicates if the action should be retried or not.
-  /// 
-  /// Implementing classes should override this property and make sure the 
+  ///
+  /// Implementing classes should override this property and make sure the
   /// correct value is returned based on the [code] value.
   bool get shouldRetry;
 }

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/noop_in_app_purchase.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:in_app_purchase_platform_interface/src/types/purchase_details.dart';
-
 import 'in_app_purchase_platform.dart';
 
-class NoopInAppPurchase extends InAppPurchasePlatform { }
+class NoopInAppPurchase extends InAppPurchasePlatform {}