fix(authenticator): show loading spinner only on clicked sign-in button

When clicking 'with password' or 'with passkey', only the clicked button
shows a loading spinner while the other is disabled. Previously both
buttons showed spinners which was confusing.

Changes:
- Add busyButtonKey and isBusyFor() to AuthenticatorState to track which
  button initiated the busy state
- Update _AmplifyElevatedButtonState to show spinner only for the active
  button (others just disable)
- Pass buttonKey from each sign-in button's onPressed handler
- Fix ContinueSignInWithFirstFactorSelectionForm to track which action
  (password or factor) is submitting, showing spinner only on that button
- Update MockAuthenticatorState in tests to implement new members

Author: cadivus

packages/authenticator/amplify_authenticator/lib/src/state/authenticator_state.dart

@@ -71,15 +71,32 @@ class AuthenticatorState extends ChangeNotifier {
     }
   }
 
-  /// Indicates if the form is currently in a loading state
+  /// Indicates if the form is currently in a loading state.
   ///
-  /// Will be set to true when an asynchronous action (such as login) in
-  /// initiated, and will be set to false when that asynchronous action completes
+  /// Will be set to true when an asynchronous action (such as login) is
+  /// initiated, and will be set to false when that asynchronous action completes.
   bool get isBusy => _isBusy;
 
+  /// The [ButtonResolverKey] of the button that initiated the current busy
+  /// state, or `null` when idle or when the originating button is unknown.
+  ///
+  /// Use [isBusyFor] to check whether a specific button should show its
+  /// loading indicator.
+  ButtonResolverKey? get busyButtonKey => _busyButtonKey;
+
+  /// Returns `true` when the authenticator is busy **and** the operation was
+  /// initiated by a button with the given [key].
+  ///
+  /// Buttons whose [key] does not match should disable themselves without
+  /// showing a spinner.
+  bool isBusyFor(ButtonResolverKey key) => _isBusy && _busyButtonKey == key;
+
   bool _isBusy = false;
-  void _setIsBusy(bool busy) {
+  ButtonResolverKey? _busyButtonKey;
+
+  void _setIsBusy(bool busy, {ButtonResolverKey? buttonKey}) {
     _isBusy = busy;
+    _busyButtonKey = busy ? buttonKey : null;
     notifyListeners();
   }
 
@@ -510,13 +527,16 @@ class AuthenticatorState extends ChangeNotifier {
     _setIsBusy(false);
   }
 
-  /// Sign in with [username], and [password]
-  Future<void> signIn() async {
+  /// Sign in with [username], and [password].
+  ///
+  /// The optional [buttonKey] identifies which button initiated the operation
+  /// so that only that button displays a loading spinner.
+  Future<void> signIn({ButtonResolverKey? buttonKey}) async {
     if (!_formKey.currentState!.validate()) {
       return;
     }
 
-    _setIsBusy(true);
+    _setIsBusy(true, buttonKey: buttonKey);
 
     TextInput.finishAutofillContext(shouldSave: true);
 
@@ -540,11 +560,17 @@ class AuthenticatorState extends ChangeNotifier {
   }
 
   /// Sign in with username and password, bypassing any passwordless preference.
-  Future<void> signInWithPassword() async {
+  ///
+  /// The optional [buttonKey] identifies which button initiated the operation
+  /// so that only that button displays a loading spinner.
+  Future<void> signInWithPassword({ButtonResolverKey? buttonKey}) async {
     if (!_formKey.currentState!.validate()) {
       return;
     }
-    _setIsBusy(true);
+    _setIsBusy(
+      true,
+      buttonKey: buttonKey ?? ButtonResolverKey.signInWithPassword,
+    );
     TextInput.finishAutofillContext(shouldSave: true);
     _authBloc.add(
       AuthSignIn(
@@ -561,12 +587,17 @@ class AuthenticatorState extends ChangeNotifier {
   /// Sign in with a specific passwordless factor (webAuthn, emailOtp, smsOtp).
   ///
   /// Only validates that a username is present — password validation is skipped
-  /// since passwordless methods don't require one.
-  Future<void> signInWithFactor(AuthFactorType factor) async {
+  /// since passwordless methods don't require one. The optional [buttonKey]
+  /// identifies which button initiated the operation so that only that button
+  /// displays a loading spinner.
+  Future<void> signInWithFactor(
+    AuthFactorType factor, {
+    ButtonResolverKey? buttonKey,
+  }) async {
     if (_username.trim().isEmpty) {
       return;
     }
-    _setIsBusy(true);
+    _setIsBusy(true, buttonKey: buttonKey);
     _authBloc.add(
       AuthSignIn(
         AuthPasswordlessSignInData(

packages/authenticator/amplify_authenticator/lib/src/widgets/button.dart

@@ -109,10 +109,14 @@ class _AmplifyElevatedButtonState
   Widget build(BuildContext context) {
     final buttonResolver = stringResolver.buttons;
     final loadingIndicator = widget.loadingIndicator;
+    final isThisButtonBusy = state.isBusyFor(widget.labelKey);
+    final isBusyNoKey = state.isBusy && state.busyButtonKey == null;
+    final showSpinner =
+        (isThisButtonBusy || isBusyNoKey) && loadingIndicator != null;
     final onPressed = state.isBusy
         ? null
         : () => widget.onPressed(context, state);
-    final child = state.isBusy && loadingIndicator != null
+    final child = showSpinner
         ? loadingIndicator
         : Row(
             mainAxisSize: MainAxisSize.min,
@@ -181,7 +185,7 @@ class SignInButton extends AuthenticatorElevatedButton {
 
   @override
   void onPressed(BuildContext context, AuthenticatorState state) =>
-      state.signIn();
+      state.signIn(buttonKey: labelKey);
 }
 
 /// A sign-in button that always uses the password flow, bypassing any
@@ -194,7 +198,7 @@ class SignInWithPasswordButton extends AuthenticatorElevatedButton {
 
   @override
   void onPressed(BuildContext context, AuthenticatorState state) =>
-      state.signInWithPassword();
+      state.signInWithPassword(buttonKey: labelKey);
 }
 
 /// Password sign-in button with "Sign in with password" label.
@@ -206,7 +210,7 @@ class SignInWithPasswordLabeledButton extends AuthenticatorElevatedButton {
 
   @override
   void onPressed(BuildContext context, AuthenticatorState state) =>
-      state.signInWithPassword();
+      state.signInWithPassword(buttonKey: labelKey);
 }
 
 /// A sign-in button that uses the passkey (passwordless) flow.
@@ -218,7 +222,7 @@ class SignInWithPasskeyButton extends AuthenticatorElevatedButton {
 
   @override
   void onPressed(BuildContext context, AuthenticatorState state) =>
-      state.signIn();
+      state.signIn(buttonKey: labelKey);
 }
 
 /// A sign-in button for a specific [AuthFactorType] (passwordless).
@@ -243,7 +247,7 @@ class FactorSignInButton extends AuthenticatorElevatedButton {
 
   @override
   void onPressed(BuildContext context, AuthenticatorState state) =>
-      state.signInWithFactor(factor);
+      state.signInWithFactor(factor, buttonKey: labelKey);
 }
 
 /// {@category Prebuilt Widgets}

packages/authenticator/amplify_authenticator/lib/src/widgets/form.dart

@@ -931,6 +931,9 @@ class _ContinueSignInWithFirstFactorSelectionFormState
   bool _isPasskeySupported = false;
   bool _isPasskeySupportChecked = false;
   bool _isSubmitting = false;
+
+  /// Tracks which action initiated the submission (password or a factor key).
+  String? _submittingAction;
   final _passwordController = TextEditingController();
 
   @override
@@ -1003,7 +1006,10 @@ class _ContinueSignInWithFirstFactorSelectionFormState
     final password = _passwordController.text.trim();
     if (password.isEmpty) return;
 
-    setState(() => _isSubmitting = true);
+    setState(() {
+      _isSubmitting = true;
+      _submittingAction = 'password';
+    });
 
     final confirm = AuthConfirmSignInData(confirmationValue: password);
     final bloc = InheritedAuthBloc.of(context, listen: false);
@@ -1012,12 +1018,18 @@ class _ContinueSignInWithFirstFactorSelectionFormState
     await state.nextBlocEvent();
 
     if (mounted) {
-      setState(() => _isSubmitting = false);
+      setState(() {
+        _isSubmitting = false;
+        _submittingAction = null;
+      });
     }
   }
 
   Future<void> _selectFactor(AuthFactorType factor) async {
-    setState(() => _isSubmitting = true);
+    setState(() {
+      _isSubmitting = true;
+      _submittingAction = factor.value;
+    });
 
     final confirm = AuthConfirmSignInData(confirmationValue: factor.value);
     final bloc = InheritedAuthBloc.of(context, listen: false);
@@ -1026,7 +1038,10 @@ class _ContinueSignInWithFirstFactorSelectionFormState
     await state.nextBlocEvent();
 
     if (mounted) {
-      setState(() => _isSubmitting = false);
+      setState(() {
+        _isSubmitting = false;
+        _submittingAction = null;
+      });
     }
   }
 
@@ -1088,10 +1103,10 @@ class _ContinueSignInWithFirstFactorSelectionFormState
             const SizedBox(height: 12),
             SizedBox(
               width: double.infinity,
-              child: _isSubmitting
+              child: _submittingAction == 'password'
                   ? const Center(child: CircularProgressIndicator())
                   : ElevatedButton(
-                      onPressed: _submitPassword,
+                      onPressed: _isSubmitting ? null : _submitPassword,
                       child: Text(
                         buttonResolver.resolve(
                           context,
@@ -1127,15 +1142,19 @@ class _ContinueSignInWithFirstFactorSelectionFormState
               padding: const EdgeInsets.only(bottom: 8),
               child: SizedBox(
                 width: double.infinity,
-                child: OutlinedButton(
-                  onPressed: _isSubmitting ? null : () => _selectFactor(factor),
-                  child: Text(
-                    buttonResolver.resolve(
-                      context,
-                      _buttonKeyForFactor(factor),
-                    ),
-                  ),
-                ),
+                child: _submittingAction == factor.value
+                    ? const Center(child: CircularProgressIndicator())
+                    : OutlinedButton(
+                        onPressed: _isSubmitting
+                            ? null
+                            : () => _selectFactor(factor),
+                        child: Text(
+                          buttonResolver.resolve(
+                            context,
+                            _buttonKeyForFactor(factor),
+                          ),
+                        ),
+                      ),
               ),
             ),
           ),

packages/authenticator/amplify_authenticator/test/authenticated_view_test.dart

@@ -234,6 +234,12 @@ class MockAuthenticatorState extends Mock implements AuthenticatorState {
   @override
   bool get isBusy => _isBusy;
 
+  @override
+  ButtonResolverKey? get busyButtonKey => null;
+
+  @override
+  bool isBusyFor(ButtonResolverKey key) => _isBusy && busyButtonKey == key;
+
   set isBusy(bool busy) {
     _isBusy = busy;
   }