win32 6, Swift Package Manager, and a toolchain refresh (6.0.0-dev.1)

[hpoul]

Makes the plugin installable and buildable again on the current toolchain, and adds Swift Package Manager support. Targets 6.0.0-dev.1.

The motivating case: an app that wants authenticationRequired: false to hold an OAuth refresh token could not adopt this plugin at all. Three separate blockers, each verified with a build rather than an analyze.

1. win32 pin made the plugin unresolvable

Every published 5.x pinned win32 >=2.0.0 <6.0.0, so it could not resolve alongside package_info_plus >=10.1.0, which needs win32 ^6.0.1:

biometric_storage >=5.0.0 depends on win32 >=2.0.0 <6.0.0
package_info_plus >=10.1.0 depends on win32 ^6.0.1
=> version solving failed

Lifting the pin means porting to the win32 6.0 API: TEXT() is gone in favour of String.toPcwstr()/toPwstr(), the Cred* calls return Win32Result<bool> carrying the last-error code instead of a BOOL plus GetLastError(), and the enum constants are top-level extension types. Allocations moved into an Arena.

This was never a Windows-only bug. lib/biometric_storage.dart re-exports the Windows implementation under if (dart.library.io), and Flutter generates dart_plugin_registrant.dart for every platform at once. An iOS release build of a consuming app contains:

import 'package:biometric_storage/biometric_storage.dart' as biometric_storage;
...
} else if (Platform.isWindows) {
  biometric_storage.Win32BiometricStoragePlugin.registerWith();

So a package:win32 break fails an iOS build. A federated biometric_storage_windows split would not change that — the registrant would import that package instead, on every platform. The defence is a compile: test/biometric_storage_test.dart now imports the public barrel rather than src/, so flutter test on any host compiles the win32 bindings, and CI runs the suite on Windows too. Verified by reintroducing a TEXT() call and watching the original error reappear as a test failure.

Also fixed while in there: writing an empty value reached Uint8List.toNative(), which rejects empty lists. And the fileName: key under windows: was a web-only key the tool never read.

2. Swift Package Manager

Flutter 3.44+ defaults to SwiftPM and falls back to CocoaPods for any plugin without a Package.swift — so adding this plugin to a migrated app silently regenerated its Podfiles. The CocoaPods registry also goes read-only on 2 December 2026.

Both are shipped: a Package.swift (with the FlutterFramework dependency the tool now expects) alongside the podspec. The sources moved to darwin/ under sharedDarwinSource: true, which removes the symlink ios/Classes used to reach into macos/Classes and the Objective-C shim — neither survives a SwiftPM target.

Verified by building an app that also depends on package_info_plus ^10.2.1: iOS and macOS both build with no Podfile generated, and the plugin's Swift symbols are in the linked binaries. Then verified again with SwiftPM disabled, so the podspec path still works.

Visible change: the macOS plugin class is BiometricStoragePlugin rather than BiometricStorageMacOSPlugin, and iOS no longer vends BiometricStoragePlugin.h. Flutter generates the registrant for both, so this only matters to someone registering the plugin by hand.

3. Staleness

Last stable was 5.0.1, roughly two years old.

• Android: AGP 8.1.4 → 8.13.2, Kotlin 2.0.21 → 2.2.20, compileSdk 35 → 36, fragment-ktx 1.9.0, core-ktx 1.18.0, slf4j 2.0.18, kotlin-logging 8. lintOptions was removed in AGP 9, so it became lint. The plugin no longer applies the Kotlin Gradle Plugin itself — AGP 9 warns about that and future Flutter releases reject it.
• androidx.biometric is held at 1.4.0-alpha05 deliberately. alpha06 added minCompileMinorSdk=1, which forces consumers to compileSdk 36.1. AGP 9.1 ignores that field, AGP 9.3 enforces it — so a bump to alpha07 raises every consumer's floor invisibly. alpha05 is the newest that asks only for compileSdk 35.
• Example on AGP 9.3.2 / Gradle 9.5.0 / Kotlin 2.4.10 — ahead of the flutter create template on purpose, which is what caught the item above.
• CI: actions/checkout@v1 → v4, a web job that set up Flutter on Windows and then did nothing → a real Windows test run, plus formatting and --fatal-infos analysis, and an assertion that no Podfile appeared. The example is a separate package, so analyze and test now run there too.
• Dart sources reformatted with the current formatter (its own commit), logging_appenders 1.1 → 2.0 in the example, and its widget test — which had never passed, asserting a string the UI never contained — replaced with a real smoke test.

Fixes

• Fixes Add Swift Package Manager support #144 — Swift Package Manager support.
• Fixes Android 16+: canAuthenticate() throws "Unknown response code {21}" (BIOMETRIC_ERROR_NOT_ENABLED_FOR_APPS) #148 — canAuthenticate() threw on any status code it did not recognise. Android 16 added BIOMETRIC_ERROR_NOT_ENABLED_FOR_APPS (21) and every call blew up. Unmapped codes now report as CanAuthenticateResponse.statusUnknown and log, which is version-independent rather than a fix for code 21 specifically.
• Fixes Android build fails on 5.0.0+4 with 'Could not find method jvmToolchain' #107 — Could not find method jvmToolchain(). The call is gone; the JVM target is set inside pluginManager.withPlugin('org.jetbrains.kotlin.android').
• Fixes The issue with strictly fixed Java 17 was resolved, but the changes were (accidentally?) rolled back in newer versions #140 — the same jvmToolchain(17) that biometric_storage does not build with Java 21 #117 removed and a9717ef reinstated. Without it a JDK 17 toolchain is no longer required; the example builds under JDK 25.

Supersedes

• Supersedes Update win32's constants #133 — its win32 constant update and its SwiftPM migration are both covered here. This PR shares the darwin sources through sharedDarwinSource rather than duplicating them under ios/ and macos/.
• Supersedes Update to latest flutter #100 — "Update to latest flutter" (2023), pubspec constraints only.

Two more are already obsolete, though not because of this PR — worth closing separately:

• Add a setting to allow biometric-only access on IOS. #50, iosBiometricOnly, shipped as darwinBiometricOnly in 5.0.1.
• Optional custom prompt per action #13, per-action custom prompts, shipped as the promptInfo parameter on read/write in 5.0.0.

Documentation corrections

The README presented FlutterFragmentActivity and a Theme.AppCompat theme as unconditional requirements, which is what made adoption look invasive. Both are conditions on showing a prompt:

• withAuth returns straight to its callback when authenticationRequired is false, so attachedActivity is never read and BiometricPrompt is never constructed.
• androidx.biometric only draws its own AppCompat dialog when isUsingFingerprintDialog() holds: SDK_INT < 28, API 28 without a fingerprint sensor, or a device on the shouldUseFingerprintForCrypto list. The README said "Android < 29".

Also documented: IosPromptInfo.saveTitle/accessTitle are not rendered on a Face ID device. Checked on an iPhone Xr running iOS 18.7.9 with a build that set the deprecated kSecUseOperationPrompt and its replacement LAContext.localizedReason to different marker strings — a screen recording of a read shows neither. They still reach the system, and Touch ID and macOS do draw them. kSecUseOperationPrompt, deprecated since iOS 14 / macOS 11, is replaced by localizedReason in this PR; the strings were invisible under Face ID before the change too.

Breaking

Requires Dart 3.10 / Flutter 3.44, which is win32 6.0.1's own floor and where SwiftPM became the default. The plugin still declares AGP 8.13.2 rather than 9.x, so it does not drag consumers onto Gradle 9.

Not addressed

• macOS stays out of the CI build matrix: the example's keychain-access-groups entitlement resolves $(AppIdentifierPrefix) from the signing team, so its Runner cannot be built without a development certificate.
• android.builtInKotlin cannot be turned on yet — every AGP from 9.1.0 to 9.3.2 bundles KGP 2.2.10, below the 2.2.20 Flutter treats as a hard error.
• Remove dart:html #145 (dart:html) was already fixed on main in 5.1.0-rc.3; 5.0.1 is the last stable, so this release is the first to carry it to users.
• [Windows] Where is the windows implementation in 5.0.0? #136 is worth re-testing against this branch — the generated registrant does contain the Windows branch — but no specific fix was made for it.
• Behavioural bug reports (AEADBadTagException when calling getStorage #121, Periodic PlattformException: open failed ENOENT #126, Android15 java.security.ProviderException: Keystore key generation failed #127, iOS: errSecAuthFailed (-25293) is not mapped to an AuthException #128, Could not determine the dependencies of task ':biometric_storage:bundleLibCompileToJarDebug'. #131, ANR on Android 12 Device #142, [Crash App]: Crash app on Samsung Note 10 Plus #143) are untouched; each needs its own investigation.

Not published to pub.dev.

🤖 Generated with Claude Code

[hpoul]

Closed as a side effect of renaming the branch claude/trusting-kepler-add7db → win32-6-and-swiftpm; GitHub did not retarget it and it cannot be reopened now that the old head ref is gone.

Superseded by #150, same commits.