Dismiss the previous sign-in error when a new attempt starts

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Error messages are localized (English and Japanese). A request that fails without the API's `error_message` shows "Something went wrong while communicating with the server. Please try again later." (`NATIVEAPPTEMPLATE-2001`); developer-only errors (`NATIVEAPPTEMPLATE-1001`, `2002`–`2008`, `4001`–`4004`) show "An unexpected error occurred." The API's `error_message` is shown without the " [Status: nnn]" suffix. Error codes are unchanged; status codes, field names and underlying errors go to the log (`CodedError.debugDescription`)
 
 ### Fixed
+- A failed sign-in's error message stayed on screen after the next attempt signed in; a new attempt now dismisses it
 - Debug builds lost the local API when launched other than from Xcode, e.g. from the Home Screen or when iOS relaunched the app after its language was changed in Settings: the endpoint came only from the scheme's environment variables, which only Xcode passes. It now comes from `API.xcconfig` (override it in the gitignored `API.local.xcconfig`) and is built into `Info.plist`; `NATIVEAPPTEMPLATE_API_*` environment variables still win. The scheme no longer sets them
 
 ### Added

NativeAppTemplate/UI/App Root/SignInEmailAndPasswordViewModel.swift

@@ -66,6 +66,10 @@ final class SignInEmailAndPasswordViewModel {
             let theEmail = email.trimmingCharacters(in: whitespacesAndNewlines)
             let thePassword = password.trimmingCharacters(in: whitespacesAndNewlines)
 
+            // The previous attempt's error no longer applies, and would stay over the
+            // shops after this attempt signs in
+            messageBus.dismiss()
+
             do {
                 isLoggingIn = true
                 try await sessionController.login(email: theEmail, password: thePassword)

NativeAppTemplateTests/UI/App Root/SignInEmailAndPasswordViewModelTest.swift

@@ -160,6 +160,25 @@ struct SignInEmailAndPasswordViewModelTest {
         #expect(viewModel.isLoggingIn == false)
     }
 
+    @Test("A new attempt dismisses the previous attempt's error")
+    func signInDismissesPreviousError() async {
+        let viewModel = SignInEmailAndPasswordViewModel(
+            sessionController: sessionController,
+            messageBus: messageBus
+        )
+        // TestSessionController starts signed in; the wait below must see this sign-in
+        sessionController.userState = .notLoggedIn
+        messageBus.post(message: Message(error: NativeAppTemplateAPIError.requestFailed(nil, 401, "Invalid email or password.")))
+
+        viewModel.email = "test@example.com"
+        viewModel.password = "password123"
+        viewModel.signIn()
+
+        await waitUntil { sessionController.userState == .loggedIn && !viewModel.isLoggingIn }
+
+        #expect(messageBus.messageVisible == false)
+    }
+
     @Test
     func signInError() async {
         // Simulate an error by setting the sessionController to throw an error