Null safety migration

example/lib/main.dart

@@ -18,7 +18,6 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> {
-
   final TextEditingController controller = new CreditCardMaskedTextController();
 
   @override
@@ -76,7 +75,8 @@ class _MyAppState extends State<MyApp> {
 
   void _getCustomer() async {
     try {
-      final customer = await CustomerSession.instance.retrieveCurrentCustomer();
+      final customer =
+          await CustomerSession.instance!.retrieveCurrentCustomer();
       print(customer);
     } catch (error) {
       print(error);
@@ -91,9 +91,9 @@ class _MyAppState extends State<MyApp> {
     StripeCard card = new StripeCard(
         number: '4242 4242 4242 4242', cvc: '713', expMonth: 5, expYear: 2019);
     card.name = 'Jhonny Bravo';
-    Stripe.instance.createCardToken(card).then((c) {
+    Stripe.instance!.createCardToken(card).then((c) {
       print(c);
-      return CustomerSession.instance.addCustomerSource(c.id);
+      return CustomerSession.instance!.addCustomerSource(c.id);
     }).then((source) {
       print(source);
     }).catchError((error) {
@@ -103,10 +103,11 @@ class _MyAppState extends State<MyApp> {
 
   void _changeDefaultCard() async {
     try {
-      final customer = await CustomerSession.instance.retrieveCurrentCustomer();
+      final customer =
+          await CustomerSession.instance!.retrieveCurrentCustomer();
       final card = customer.sources[1].asCard();
       final v =
-          await CustomerSession.instance.updateCustomerDefaultSource(card.id);
+          await CustomerSession.instance!.updateCustomerDefaultSource(card!.id);
       print(v);
     } catch (error) {
       print(error);
@@ -115,17 +116,18 @@ class _MyAppState extends State<MyApp> {
 
   void _deleteCard() async {
     try {
-      final customer = await CustomerSession.instance.retrieveCurrentCustomer();
-      String id;
+      final customer =
+          await CustomerSession.instance!.retrieveCurrentCustomer();
+      late String id;
       for (var c in customer.sources) {
-        StripeCard card = c.asCard();
+        StripeCard? card = c.asCard();
         if (card != null) {
           id = card.id;
           break;
         }
       }
 
-      final v = await CustomerSession.instance.deleteCustomerSource(id);
+      final v = await CustomerSession.instance!.deleteCustomerSource(id);
       print(v);
     } catch (error) {
       print(error);
@@ -153,7 +155,7 @@ class _MyAppState extends State<MyApp> {
   }
 
   Map<String, String> _getHeaders(
-      {String accessToken,
+      {required String accessToken,
       String acceptType = ContentTypeJson,
       String contentType = ContentTypeJson}) {
     final Map<String, String> headers = new Map<String, String>();
@@ -173,7 +175,7 @@ class _MyAppState extends State<MyApp> {
 class CardItem extends StatelessWidget {
   final StripeCard card;
 
-  const CardItem({Key key, this.card}) : super(key: key);
+  const CardItem({Key? key, required this.card}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

lib/card_utils.dart

@@ -12,27 +12,23 @@ const int MAX_LENGTH_COMMON = 19;
 // because Diners Club has one more space, but one less digit.
 const int MAX_LENGTH_AMEX_DINERS = 17;
 
-/**
- * Checks the input string to see whether or not it is a valid card number, possibly
- * with groupings separated by spaces or hyphens.
- *
- * @param cardNumber a String that may or may not represent a valid card number
- * @return {@code true} if and only if the input value is a valid card number
- */
+/// Checks the input string to see whether or not it is a valid card number, possibly
+/// with groupings separated by spaces or hyphens.
+///
+/// @param cardNumber a String that may or may not represent a valid card number
+/// @return {@code true} if and only if the input value is a valid card number
 bool isValidCardNumber(String cardNumber) {
-  String normalizedNumber = removeSpacesAndHyphens(cardNumber);
-  return isValidLuhnNumber(normalizedNumber) &&
-      isValidCardLength(normalizedNumber);
+  String? normalizedNumber = removeSpacesAndHyphens(cardNumber);
+  return isValidLuhnNumber(normalizedNumber ?? '') &&
+      isValidCardLength(normalizedNumber ?? '', cardBrand: '');
 }
 
-/**
- * Checks the input string to see whether or not it is a valid Luhn number.
- *
- * @param cardNumber a String that may or may not represent a valid Luhn number
- * @return {@code true} if and only if the input value is a valid Luhn number
- */
+/// Checks the input string to see whether or not it is a valid Luhn number.
+///
+/// @param cardNumber a String that may or may not represent a valid Luhn number
+/// @return {@code true} if and only if the input value is a valid Luhn number
 bool isValidLuhnNumber(String cardNumber) {
-  if (cardNumber == null) {
+  if (cardNumber.isEmpty) {
     return false;
   }
 
@@ -45,7 +41,7 @@ bool isValidLuhnNumber(String cardNumber) {
       return false;
     }
 
-    int digitInteger = getNumericValue(c);
+    int digitInteger = getNumericValue(c) ?? 0;
     isOdd = !isOdd;
 
     if (isOdd) {
@@ -62,19 +58,17 @@ bool isValidLuhnNumber(String cardNumber) {
   return sum % 10 == 0;
 }
 
-/**
- * Checks to see whether the input number is of the correct length, given the assumed brand of
- * the card. This function does not perform a Luhn check.
- *
- * @param cardNumber the card number with no spaces or dashes
- * @param cardBrand a {@link CardBrand} used to get the correct size
- * @return {@code true} if the card number is the correct length for the assumed brand
- */
-bool isValidCardLength(String cardNumber, {String cardBrand}) {
-  if (cardBrand == null) {
+/// Checks to see whether the input number is of the correct length, given the assumed brand of
+/// the card. This function does not perform a Luhn check.
+///
+/// @param cardNumber the card number with no spaces or dashes
+/// @param cardBrand a {@link CardBrand} used to get the correct size
+/// @return {@code true} if the card number is the correct length for the assumed brand
+bool isValidCardLength(String cardNumber, {required String cardBrand}) {
+  if (cardBrand.isEmpty) {
     cardBrand = getPossibleCardType(cardNumber, shouldNormalize: false);
   }
-  if (cardNumber == null || StripeCard.UNKNOWN == cardBrand) {
+  if (cardNumber.isEmpty || StripeCard.UNKNOWN == cardBrand) {
     return false;
   }
 
@@ -96,7 +90,7 @@ String getPossibleCardType(String cardNumber, {bool shouldNormalize = true}) {
 
   String spacelessCardNumber = cardNumber;
   if (shouldNormalize) {
-    spacelessCardNumber = removeSpacesAndHyphens(cardNumber);
+    spacelessCardNumber = removeSpacesAndHyphens(cardNumber) ?? '';
   }
 
   if (hasAnyPrefix(spacelessCardNumber, StripeCard.PREFIXES_AMERICAN_EXPRESS)) {

lib/credit_card_mask_controller.dart

@@ -2,17 +2,17 @@ import 'package:flutter/material.dart';
 import 'package:stripe_api/stripe_api.dart';
 
 class CreditCardMaskedTextController extends TextEditingController {
-  CreditCardMaskedTextController({String text}) : super(text: text) {
-    this._translator = CreditCardMaskedTextController._getDefaultTranslator();
+  CreditCardMaskedTextController({String text = ''}) : super(text: text) {
+    _translator = CreditCardMaskedTextController._getDefaultTranslator();
 
-    this.addListener(() {
-      this._updateText(this.text);
+    addListener(() {
+      _updateText(this.text);
     });
 
-    this._updateText(this.text);
+    _updateText(this.text);
   }
 
-  static const CARD_MASKS = const {
+  static const Map<String, String> CARD_MASKS = {
     StripeCard.UNKNOWN: '0000 0000 0000 0000',
     StripeCard.AMERICAN_EXPRESS: '0000 000000 00000',
     StripeCard.DISCOVER: '0000 0000 0000 0000',
@@ -23,32 +23,32 @@ class CreditCardMaskedTextController extends TextEditingController {
     StripeCard.UNIONPAY: '0000 0000 0000 0000',
   };
 
-  Map<String, RegExp> _translator;
+  late Map<String, RegExp> _translator;
   String _lastUpdatedText = '';
 
   void _updateText(String text) {
-    if (text != null) {
-      final cardType = getPossibleCardType(text, shouldNormalize: true);
-      final mask = CARD_MASKS[cardType];
-      this.text = this._applyMask(mask, text);
+    if (text.isNotEmpty) {
+      final String cardType = getPossibleCardType(text, shouldNormalize: true);
+      final String mask = CARD_MASKS[cardType]!;
+      this.text = _applyMask(mask, text);
     } else {
       this.text = '';
     }
-    this._lastUpdatedText = this.text;
+    _lastUpdatedText = this.text;
   }
 
   void _moveCursorToEnd() {
-    var text = this._lastUpdatedText;
-    this.selection = TextSelection.fromPosition(
-      TextPosition(offset: (text ?? '').length),
+    var text = _lastUpdatedText;
+    selection = TextSelection.fromPosition(
+      TextPosition(offset: text.length),
     );
   }
 
   @override
   set text(String newText) {
     if (super.text != newText) {
       super.text = newText;
-      this._moveCursorToEnd();
+      _moveCursorToEnd();
     }
   }
 
@@ -90,8 +90,8 @@ class CreditCardMaskedTextController extends TextEditingController {
       }
 
       // apply translator if match
-      if (this._translator.containsKey(maskChar)) {
-        if (this._translator[maskChar].hasMatch(valueChar)) {
+      if (_translator.containsKey(maskChar)) {
+        if (_translator[maskChar]!.hasMatch(valueChar)) {
           result += valueChar;
           maskCharIndex += 1;
         }

lib/ephemeral_key_manager.dart

@@ -9,7 +9,7 @@ import 'stripe_error.dart';
 ///
 ///
 ///
-typedef Future<String> EphemeralKeyProvider(String apiVersion);
+typedef EphemeralKeyProvider = Future<String> Function(String apiVersion);
 
 ///
 ///
@@ -26,28 +26,28 @@ class EphemeralKey extends StripeJsonModel {
 
   static const String NULL = "null";
 
-  String _id;
-  int _created;
-  int _expires;
-  bool _liveMode;
-  String _customerId;
-  String _object;
-  String _secret;
-  String _type;
-  DateTime _createdAt;
-  DateTime _expiresAt;
+  late String _id;
+  late int _created;
+  late int _expires;
+  late bool _liveMode;
+  late String _customerId;
+  late String _object;
+  late String _secret;
+  late String _type;
+  late DateTime _createdAt;
+  late DateTime _expiresAt;
 
   EphemeralKey.fromJson(Map<String, dynamic> json) {
-    _id = optString(json, FIELD_ID);
-    _created = optInteger(json, FIELD_CREATED);
-    _expires = optInteger(json, FIELD_EXPIRES);
-    _liveMode = optBoolean(json, FIELD_LIVEMODE);
+    _id = optString(json, FIELD_ID) ?? '';
+    _created = optInteger(json, FIELD_CREATED) ?? -1;
+    _expires = optInteger(json, FIELD_EXPIRES) ?? -1;
+    _liveMode = optBoolean(json, FIELD_LIVEMODE) ?? false;
     _customerId = json[FIELD_ASSOCIATED_OBJECTS][0][FIELD_ID];
     _type = json[FIELD_ASSOCIATED_OBJECTS][0][FIELD_TYPE];
-    _object = optString(json, FIELD_OBJECT);
-    _secret = optString(json, FIELD_SECRET);
-    _createdAt = new DateTime.fromMillisecondsSinceEpoch(_created);
-    _expiresAt = new DateTime.fromMillisecondsSinceEpoch(_expires);
+    _object = optString(json, FIELD_OBJECT) ?? '';
+    _secret = optString(json, FIELD_SECRET) ?? '';
+    _createdAt = DateTime.fromMillisecondsSinceEpoch(_created);
+    _expiresAt = DateTime.fromMillisecondsSinceEpoch(_expires);
   }
 
   String get id => _id;
@@ -90,7 +90,7 @@ class EphemeralKey extends StripeJsonModel {
 ///
 ///
 class EphemeralKeyManager {
-  EphemeralKey _ephemeralKey;
+  EphemeralKey? _ephemeralKey;
   final EphemeralKeyProvider ephemeralKeyProvider;
   final int timeBufferInSeconds;
 
@@ -99,28 +99,28 @@ class EphemeralKeyManager {
   ///
   ///
   ///
-  Future<EphemeralKey> retrieveEphemeralKey() async {
+  Future<EphemeralKey?> retrieveEphemeralKey() async {
     if (_shouldRefreshKey()) {
       String key;
       try {
         key = await ephemeralKeyProvider(API_VERSION);
       } catch (error) {
-        final e = new StripeAPIError(null, {
+        final e = StripeAPIError('', {
           StripeAPIError.FIELD_MESSAGE:
               "Failed to retrive ephemeralKey from server",
         });
-        throw new StripeAPIException(e);
+        throw StripeAPIException(e);
       }
 
       try {
         Map<String, dynamic> decodedKey = json.decode(key);
-        _ephemeralKey = new EphemeralKey.fromJson(decodedKey);
+        _ephemeralKey = EphemeralKey.fromJson(decodedKey);
       } catch (error) {
-        final e = new StripeAPIError(null, {
+        final e = StripeAPIError('', {
           StripeAPIError.FIELD_MESSAGE:
               "Failed to parse Ephemeral Key, Please return the response as it is as you recieved from stripe server",
         });
-        throw new StripeAPIException(e);
+        throw StripeAPIException(e);
       }
 
       return _ephemeralKey;
@@ -138,7 +138,7 @@ class EphemeralKeyManager {
     }
 
     DateTime now = DateTime.now();
-    final diff = _ephemeralKey.expiresAt.difference(now).abs();
+    final diff = _ephemeralKey!.expiresAt.difference(now).abs();
     return diff.inSeconds < timeBufferInSeconds;
   }
 }

lib/model/address.dart

@@ -10,12 +10,12 @@ class Address extends StripeJsonModel {
   static const String FIELD_POSTAL_CODE = "postal_code";
   static const String FIELD_STATE = "state";
 
-  String city;
-  String country;
-  String line1;
-  String line2;
-  String postalCode;
-  String state;
+  String? city;
+  String? country;
+  String? line1;
+  String? line2;
+  String? postalCode;
+  String? state;
 
   Address({
     this.city,
@@ -37,7 +37,7 @@ class Address extends StripeJsonModel {
 
   @override
   Map<String, dynamic> toMap() {
-    Map<String, Object> hashMap = new Map();
+    Map<String, dynamic> hashMap = {};
     hashMap[FIELD_CITY] = city;
     hashMap[FIELD_COUNTRY] = country;
     hashMap[FIELD_LINE_1] = line1;