catching username availabilty exceptions and handling as user facing error

vector/src/main/java/im/vector/app/features/onboarding/OnboardingViewModel.kt

@@ -193,7 +193,9 @@ class OnboardingViewModel @AssistedInject constructor(
     }
 
     private suspend fun checkUserNameAvailability(userName: String) {
-        when (val result = registrationWizard.registrationAvailable(userName)) {
+        runCatching { registrationWizard.registrationAvailable(userName) }.fold(
+                onSuccess = { result ->
+                    when (result) {
                         RegistrationAvailability.Available -> {
                             setState {
                                 copy(
@@ -212,6 +214,11 @@ class OnboardingViewModel @AssistedInject constructor(
                             _viewEvents.post(OnboardingViewEvents.Failure(result.failure))
                         }
                     }
+                },
+                onFailure = {
+                    _viewEvents.post(OnboardingViewEvents.Failure(it))
+                }
+        )
     }
 
     private fun withAction(action: OnboardingAction, block: (OnboardingAction) -> Unit) {

vector/src/test/java/im/vector/app/features/onboarding/OnboardingViewModelTest.kt

@@ -390,6 +390,20 @@ class OnboardingViewModelTest {
                 .finish()
     }
 
+    @Test
+    fun `given available username throws, when a register username is entered, then emits error`() = runTest {
+        viewModelWith(initialRegistrationState(A_HOMESERVER_URL))
+        fakeAuthenticationService.givenRegistrationWizard(FakeRegistrationWizard().also { it.givenUserNameIsAvailableThrows(A_USERNAME, AN_ERROR) })
+        val test = viewModel.test()
+
+        viewModel.handle(OnboardingAction.UserNameEnteredAction.Registration(A_USERNAME))
+
+        test
+                .assertStates(initialState)
+                .assertEvents(OnboardingViewEvents.Failure(AN_ERROR))
+                .finish()
+    }
+
     @Test
     fun `given available username, when a register username is entered, then emits available registration state`() = runTest {
         viewModelWith(initialRegistrationState(A_HOMESERVER_URL))

vector/src/test/java/im/vector/app/test/fakes/FakeRegistrationWizard.kt

@@ -57,6 +57,10 @@ class FakeRegistrationWizard : RegistrationWizard by mockk(relaxed = false) {
         coEvery { registrationAvailable(userName) } returns RegistrationAvailability.Available
     }
 
+    fun givenUserNameIsAvailableThrows(userName: String, cause: Throwable) {
+        coEvery { registrationAvailable(userName) } throws cause
+    }
+
     fun givenUserNameIsUnavailable(userName: String, failure: Failure.ServerError) {
         coEvery { registrationAvailable(userName) } returns RegistrationAvailability.NotAvailable(failure)
     }