fix: date breaks on iOS devices set to 12-hour time, making getTokenInfo throw FormatException

[masatoi]

Symptom

On an iOS device set to 12-hour time (Settings > General > Date & Time > 24-Hour Time = off), passing a topup QR (check) URL to PokepayClient.getTokenInfo() fails with FormatException: Invalid date format. Payment QRs (bill) are unaffected.

Cause

APIJSONEncoder in ios/Classes/SwiftPokepaySdkPlugin.swift never set a locale on its DateFormatter, so Locale.current was used.

A fixed-format DateFormatter must specify en_US_POSIX; without it, Foundation rewrites HH into h plus an AM/PM marker while the device is on 12-hour time (Apple QA1480). The date that reaches Flutter then stops being ISO8601, and Dart's DateTime.parse throws.

pokepay-server        "2026-11-20T06:56:43.091034Z"   valid ISO8601
  ↓ ios-sdk BankAPIJSONDecoder (has en_US_POSIX)
Swift Check.expiresAt  Date                            still fine here
  ↓ flutter-sdk APIJSONEncoder (no en_US_POSIX)        ← breaks here
MethodChannel          "2026-11-20T午前6:56:43.091000Z"
  ↓ Check.fromJson → DateTime.parse
Dart                   FormatException: Invalid date format

Measured on the iOS 26.5 simulator:

Locale	24-Hour Time	Before	After
ja_JP	on	2026-11-20T06:56:43.091000Z	unchanged
ja_JP	off	2026-11-20T午前6:56:43.091000Z ❌	2026-11-20T06:56:43.091000Z ✅
en_US	off	2026-11-20T6:56:43.091000 AMZ ❌	2026-11-20T06:56:43.091000Z ✅
en_US	on	2026-11-20T06:56:43.091000Z	unchanged

Payment QRs survived because lib/responses/bill.dart has no DateTime field, so the malformed string passes straight through. lib/responses/check.dart declares expiresAt as a required DateTime.

Fix

One line in APIJSONEncoder: dateFormatter.locale = Locale(identifier: "en_US_POSIX").

APIJSONEncoder is the only place that serializes response dates — it is also the only DateFormatter in the repository. The generated AutogenMethodHandlers.swift carries no encoder of its own and routes all 150 of its call sites through self.after, so this single line fixes both the hand-written and the generated paths.

Verification

Unit (encoder in isolation): extracted APIJSONEncoder from the real plugin source, compiled it, and measured all four combinations in the table above on the iOS 26.5 simulator.

End to end: created a check and a bill on dev, then ran a minimal Flutter app (depending on this SDK by local path) on an iPhone 17 Pro / iOS 26.5.

State	Device setting	CHECK	BILL
Before	ja_JP / 12-hour	FormatException: Invalid date format ❌	OK ✅
After	ja_JP / 12-hour	OK, expiresAt=2026-11-30 07:11:16.856Z ✅	OK ✅
After	ja_JP / 24-hour	OK ✅	OK ✅

The first row reproduces the reported symptom exactly. The real build resolving the Pokepay 2.2.0 pod through CocoaPods also succeeds.

Regression tests: added test/responses/check_test.dart (the first test/ in this repository). The malformed strings are the measured values above, used verbatim. flutter test passes 6/6 and flutter analyze reports No issues found!.

Impact

Before this fix, every response carrying a DateTime broke on iOS devices set to 12-hour time: Cashtray, Account (nearest_expires_at), AccountBalance, AccountCpmToken, Coupon, Message, UserTransaction.done_at on the autogen side, and others.

Already investigated

• pokepay-server is not involved: querying the dev API directly returns 2026-11-30T07:11:16.856289Z, valid ISO8601.
• ios-sdk needs no change: 2.2.0 already sets en_US_POSIX in both BankAPIJSONDecoder.swift and BankAPIDateFormatter.swift.
• Android is unaffected: the Android plugin only calls res.toString() and contains no date formatting at all (zero uses of SimpleDateFormat or Locale). The behaviour where a 12/24-hour user preference rewrites a formatter is specific to Foundation/ICU.
• Not generated code: SwiftPokepaySdkPlugin.swift carries no generated-file header, and no generate-sdk-* commit has ever touched it. No generator change is required.
• How long this has been broken: git log -S "en_US_POSIX" returns nothing across the entire history. APIJSONEncoder has looked like this since the very first commit (209976e init lib, 2021-07-08), so this is unrelated to any recent change or to 2.2.0. The symptom took its current shape once ios-sdk fixed the decoding side in a765b19 (2022-09-05).

Note

Version, tags and CHANGELOG are deliberately untouched. Please decide the release plan separately.

Out of scope for this PR

• CI has no test step, so the added tests do not run there yet. Let me know whether to add flutter test to the check job here or in a separate PR.
• The build warns that pokepay_sdk does not support Swift Package Manager and that this will become an error in a future Flutter release. Unrelated to this bug, but it will need attention.

🤖 Generated with Claude Code

https://claude.ai/code/session_01W5pXxkWbYKDAnQZDpYu1RG

[ZweWaiYanHtet]

LGTM