Handle empty linked device names

Signal/src/ViewControllers/AppSettings/Linked Devices/LinkedDevicesView.swift

@@ -994,6 +994,7 @@ class EditDeviceNameViewController: NameEditorViewController {
     override class var nameByteLimit: Int { 225 }
     override class var nameGlyphLimit: Int { 50 }
 
+    override var allowEmptyName: Bool { false }
     override var placeholderText: String? {
         OWSLocalizedString(
             "SECONDARY_ONBOARDING_CHOOSE_DEVICE_NAME_PLACEHOLDER",

Signal/src/ViewControllers/NameEditorViewController.swift

@@ -19,6 +19,7 @@ class NameEditorViewController: OWSTableViewController2 {
     class var nameByteLimit: Int { owsFail("Must be implemented by subclasses") }
     class var nameGlyphLimit: Int { owsFail("Must be implemented by subclasses") }
 
+    var allowEmptyName: Bool { true }
     var placeholderText: String? { nil }
 
     private lazy var nameField = OWSTextField(
@@ -31,7 +32,7 @@ class NameEditorViewController: OWSTableViewController2 {
             self.updateHasUnsavedChanges()
         },
         returnPressed: { [unowned self] in
-            if hasUnsavedChanges { self.didTapDone() }
+            if canSaveChanges { self.didTapDone() }
         },
     )
 
@@ -63,7 +64,7 @@ class NameEditorViewController: OWSTableViewController2 {
         if isPresentedInSheet {
             self.navigationItem.leftBarButtonItem = .cancelButton(
                 dismissingFrom: self,
-                hasUnsavedChanges: { [unowned self] in self.hasUnsavedChanges },
+                hasUnsavedChanges: { [unowned self] in self.canSaveChanges },
             )
         }
         self.navigationItem.rightBarButtonItem = .doneButton { [unowned self] in self.didTapDone() }
@@ -98,20 +99,23 @@ class NameEditorViewController: OWSTableViewController2 {
     }
 
     override var isModalInPresentation: Bool {
-        get { hasUnsavedChanges }
+        get { canSaveChanges }
         set {}
     }
 
     private func updateHasUnsavedChanges() {
-        self.hasUnsavedChanges = self.nameField.text != self.oldName
+        let hasUnsavedChanges = self.nameField.text != self.oldName
+        let hasUnallowedEmptyName = !self.allowEmptyName && self.nameField.text.isEmptyOrNil
+
+        self.navigationItem.rightBarButtonItem?.isEnabled = hasUnsavedChanges && !hasUnallowedEmptyName
     }
 
-    private var hasUnsavedChanges: Bool = false {
+    private var canSaveChanges: Bool = false {
         didSet {
-            if oldValue == hasUnsavedChanges {
+            if oldValue == canSaveChanges {
                 return
             }
-            self.navigationItem.rightBarButtonItem?.isEnabled = hasUnsavedChanges
+            self.navigationItem.rightBarButtonItem?.isEnabled = canSaveChanges
         }
     }
 

SignalServiceKit/Devices/OWSDeviceNames.swift

@@ -10,6 +10,7 @@ public import LibSignalClient
 public enum OWSDeviceNameError: Error {
     case assertionFailure
     case invalidInput
+    case emptyName
     case cryptError(_ description: String)
 }
 
@@ -98,8 +99,7 @@ public enum OWSDeviceNames {
             throw OWSDeviceNameError.assertionFailure
         }
         guard ciphertext.count > 0 else {
-            owsFailDebug("Invalid cipher text.")
-            throw OWSDeviceNameError.assertionFailure
+            throw OWSDeviceNameError.emptyName
         }
 
         // master_secret = ECDH(identity_private, ephemeral_public)

SignalServiceKit/Devices/OWSDeviceService.swift

@@ -154,9 +154,11 @@ struct OWSDeviceServiceImpl: OWSDeviceService {
                     base64String: nameCiphertext,
                     identityKeyPair: identityKeyPair,
                 )
+            } catch OWSDeviceNameError.emptyName {
+                name = nil
             } catch {
                 owsFailDebug("Failed to decrypt device name! Is this a legacy device name? \(error)")
-                name = nameCiphertext
+                name = nil
             }
         } else {
             name = nil