[local_auth_darwin] Handle when FaceID hardware is available but permissions have been denied for the app (#8348)

LocalAuth  [`-canEvaluatePolicy::`](https://developer.apple.com/documentation/localauthentication/lacontext/canevaluatepolicy(_:error:)?language=objc) returns error `LAErrorBiometryNotAvailable` when either Face ID isn't available at the hardware level, OR the Face ID is available/setup but the permissions for the app were denied.

If it returns `LAErrorBiometryNotAvailable`, also check `biometryType` since this _should_ be none if there really is no biometry, but gets populated with [`LABiometryTypeTouchID`](https://developer.apple.com/documentation/localauthentication/labiometrytype/touchid?language=objc) when the FaceID hardware is available, but permission is denied.  I tried this on a iPhone 16 Pro which has Face ID but not Touch ID support.

Fixes flutter/flutter#160083

Author: jmagman

packages/local_auth/local_auth_darwin/CHANGELOG.md

@@ -1,5 +1,6 @@
-## NEXT
+## 1.4.3
 
+* Handles when biometry hardware is available but permissions have been denied for the app.
 * Updates minimum supported SDK version to Flutter 3.22/Dart 3.4.
 
 ## 1.4.2

packages/local_auth/local_auth_darwin/darwin/Tests/FLALocalAuthPluginTests.swift

@@ -447,7 +447,7 @@ class FLALocalAuthPluginTests: XCTestCase {
     XCTAssertNil(error)
   }
 
-  func testDeviceSupportsBiometrics_withNoBiometricHardware() {
+  func testDeviceSupportsBiometrics_withBiometryNotAvailable() {
     let stubAuthContext = StubAuthContext()
     let alertFactory = StubAlertFactory()
     let viewProvider = StubViewProvider()
@@ -456,14 +456,34 @@ class FLALocalAuthPluginTests: XCTestCase {
       alertFactory: alertFactory, viewProvider: viewProvider)
 
     stubAuthContext.expectBiometrics = true
-    stubAuthContext.canEvaluateError = NSError(domain: "error", code: 0)
+    stubAuthContext.canEvaluateError = NSError(
+      domain: "error", code: LAError.biometryNotAvailable.rawValue)
 
     var error: FlutterError?
     let result = plugin.deviceCanSupportBiometricsWithError(&error)
     XCTAssertFalse(result!.boolValue)
     XCTAssertNil(error)
   }
 
+  func testDeviceSupportsBiometrics_withBiometryNotAvailableLoadedBiometryType() {
+    let stubAuthContext = StubAuthContext()
+    let alertFactory = StubAlertFactory()
+    let viewProvider = StubViewProvider()
+    let plugin = FLALocalAuthPlugin(
+      contextFactory: StubAuthContextFactory(contexts: [stubAuthContext]),
+      alertFactory: alertFactory, viewProvider: viewProvider)
+
+    stubAuthContext.expectBiometrics = true
+    stubAuthContext.biometryType = LABiometryType.touchID
+    stubAuthContext.canEvaluateError = NSError(
+      domain: "error", code: LAError.biometryNotAvailable.rawValue)
+
+    var error: FlutterError?
+    let result = plugin.deviceCanSupportBiometricsWithError(&error)
+    XCTAssertTrue(result!.boolValue)
+    XCTAssertNil(error)
+  }
+
   func testGetEnrolledBiometricsWithFaceID() {
     let stubAuthContext = StubAuthContext()
     let alertFactory = StubAlertFactory()

packages/local_auth/local_auth_darwin/darwin/local_auth_darwin/Sources/local_auth_darwin/FLALocalAuthPlugin.m

@@ -317,6 +317,11 @@ - (nullable NSNumber *)deviceCanSupportBiometricsWithError:
     if (authError.code == LAErrorBiometryNotEnrolled) {
       return @YES;
     }
+    // Biometry hardware is available, but possibly permissions were denied.
+    if (authError.code == LAErrorBiometryNotAvailable &&
+        context.biometryType != LABiometryTypeNone) {
+      return @YES;
+    }
   }
 
   return @NO;

packages/local_auth/local_auth_darwin/pubspec.yaml

@@ -2,7 +2,7 @@ name: local_auth_darwin
 description: iOS implementation of the local_auth plugin.
 repository: https://github.com/flutter/packages/tree/main/packages/local_auth/local_auth_darwin
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+local_auth%22
-version: 1.4.2
+version: 1.4.3
 
 environment:
   sdk: ^3.4.0