Consider numberless unsolvable reglock to be invalid.

feature/registration/src/main/java/org/signal/registration/screens/signallogincredentials/SignalLoginCredentialEntryViewModel.kt

@@ -225,19 +225,12 @@ class SignalLoginCredentialEntryViewModel(
             stateEmitter(inputState.copy(isLoggingIn = false, areCredentialsIncorrect = true))
           }
           is RegisterAccountError.RegistrationLock -> {
-            if (provideRegistrationLock) {
-              Log.w(TAG, "[Next] Still registration locked after providing the reglock token derived from the recovery key. Falling back to PIN entry.")
-              stateEmitter(inputState.copy(isLoggingIn = false))
-              parentEventEmitter.navigateTo(
-                RegistrationRoute.PinEntryForRegistrationLock(
-                  timeRemaining = error.data.timeRemaining,
-                  svrCredentials = error.data.svr2Credentials
-                )
-              )
-            } else {
-              Log.w(TAG, "[Next] Registration locked. Retrying with the reglock token derived from the recovery key.")
-              attemptToLogIn(inputState, aci, aep, totp, provideRegistrationLock = true, parentEventEmitter, stateEmitter)
-            }
+            // An account with no phone number can't have a registration lock enabled in the first place, and the only
+            // PIN that could clear one is behind a phone number we don't have. There is nothing to fall back to.
+            check(!provideRegistrationLock) { "[Next] Still registration locked after providing the reglock derived from the recovery key. A phone-numberless account cannot be registration locked!" }
+
+            Log.w(TAG, "[Next] Registration locked. Retrying with the reglock token derived from the recovery key.")
+            attemptToLogIn(inputState, aci, aep, totp, provideRegistrationLock = true, parentEventEmitter, stateEmitter)
           }
           is RegisterAccountError.RateLimited -> {
             Log.w(TAG, "[Next] Rate limited (retryAfter: ${error.retryAfter}).")

feature/registration/src/test/java/org/signal/registration/RegistrationEndToEndTest.kt

@@ -1895,36 +1895,6 @@ class RegistrationEndToEndTest {
     }
   }
 
-  @Test
-  fun `a reglock the entered recovery key cannot derive falls back to asking for the pin`() {
-    enableSignalLoginRegistration()
-    val login = SignalLogin(ACI.from(UUID.randomUUID()), AccountEntropyPool.generate())
-
-    networkController.onRegisterAccount = {
-      RequestResult.NonSuccess(
-        RegisterAccountError.RegistrationLock(
-          RegistrationLockResponse(
-            timeRemaining = 14.days.inWholeMilliseconds,
-            svr2Credentials = SvrCredentials(username = "svr-user", password = "svr-pass")
-          )
-        )
-      )
-    }
-
-    launchRegistrationFlow()
-
-    startSignalLoginRegistration()
-    useExistingSignalLogin()
-    enterSignalLogin(login)
-
-    // The account's reglock isn't the one the recovery key derives, so the PIN behind it is the only way in
-    waitForTag(TestTags.PIN_ENTRY_SCREEN)
-    assert(networkController.lastRegisterAccountRequest?.registrationLock == login.aep.deriveMasterKey().deriveRegistrationLock()) {
-      "Expected the derived reglock to have been tried before falling back but was ${networkController.lastRegisterAccountRequest}"
-    }
-    assert(storageController.committedData == null) { "Expected no registration data to be committed while still locked out" }
-  }
-
   @Test
   fun `restoring a remote backup after logging in with a signal login completes registration without a pin`() {
     enableSignalLoginRegistration()

feature/registration/src/test/java/org/signal/registration/screens/signallogincredentials/SignalLoginCredentialEntryViewModelTest.kt

@@ -5,6 +5,7 @@
 
 package org.signal.registration.screens.signallogincredentials
 
+import assertk.assertFailure
 import assertk.assertThat
 import assertk.assertions.containsExactly
 import assertk.assertions.hasSize
@@ -411,18 +412,13 @@ class SignalLoginCredentialEntryViewModelTest {
   }
 
   @Test
-  fun `NextClicked still registration locked after providing the reglock token falls back to PIN entry`() = runTest(testDispatcher) {
+  fun `NextClicked still registration locked after providing the reglock token throws, since there is nothing to fall back to`() = runTest(testDispatcher) {
     coEvery { mockRepository.reRegisterAccountWithoutPhoneNumber(any(), any(), any(), any(), any()) } returns
       RequestResult.NonSuccess(RegisterAccountError.RegistrationLock(registrationLockResponse()))
 
-    applyEvent(completeState(), SignalLoginCredentialEntryScreenEvents.NextClicked)
-
-    assertThat(emittedStates.last().isLoggingIn).isEqualTo(false)
-    assertThat(emittedParentEvents).hasSize(2)
-    assertThat(emittedParentEvents[1])
-      .isInstanceOf<RegistrationFlowEvent.NavigateToScreen>()
-      .prop(RegistrationFlowEvent.NavigateToScreen::route)
-      .isInstanceOf<RegistrationRoute.PinEntryForRegistrationLock>()
+    assertFailure {
+      applyEvent(completeState(), SignalLoginCredentialEntryScreenEvents.NextClicked)
+    }.isInstanceOf<IllegalStateException>()
   }
 
   @Test