refactor(ui): never save an empty username

Drops `isUsernameRequired`. The legacy form let an empty value through on an
instance where the username is optional, which is how it doubled as "remove my
username" — an incidental consequence of its submit gate, not an affordance
anything offers. The new surface does not offer it, so the rule is unconditional
and the prop that carried it is gone.

Back to the two-prop public surface: `username` and `onSaveUsername`.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015nA7S7H8uK8qPzwm1PwzoR

Author: maxyinger

packages/swingset/src/stories/fixtures/user-profile-edit-username.ts

@@ -13,7 +13,6 @@ class FormError extends Error {
 
 export interface UserProfileEditUsernameFixtureOptions {
   username?: string;
-  isRequired?: boolean;
   latency?: number;
   /** Rejects every save instead of committing it. */
   failWith?: UserProfileFormError;
@@ -22,15 +21,13 @@ export interface UserProfileEditUsernameFixtureOptions {
 /** Stands in for the model. Everything else the dialog needs belongs to the controller. */
 export function useUserProfileEditUsernameFixture({
   username: initialUsername = 'prestonxyz',
-  isRequired = false,
   latency = 800,
   failWith,
 }: UserProfileEditUsernameFixtureOptions = {}) {
   const [username, setUsername] = useState(initialUsername);
 
   return {
     username,
-    isUsernameRequired: isRequired,
     onSaveUsername: async (value: string) => {
       await new Promise(resolve => setTimeout(resolve, latency));
       if (failWith) {

packages/swingset/src/stories/user-profile-account-section.stories.tsx

@@ -24,14 +24,12 @@ export const meta: StoryMeta = {
 
 function AccountSection({
   allowMultipleAccounts,
-  isUsernameRequired,
   failWith,
 }: {
   allowMultipleAccounts: boolean;
-  isUsernameRequired?: boolean;
   failWith?: UserProfileFormError;
 }) {
-  const editUsername = useUserProfileEditUsernameFixture({ isRequired: isUsernameRequired, failWith });
+  const editUsername = useUserProfileEditUsernameFixture({ failWith });
   const [emails, setEmails] = useState<UserProfileEmail[]>(
     allowMultipleAccounts
       ? [
@@ -101,13 +99,3 @@ export function EditUsernameFails() {
     />
   );
 }
-
-/** A username the instance insists on, so clearing the field leaves the action inert. */
-export function UsernameRequired() {
-  return (
-    <AccountSection
-      allowMultipleAccounts={false}
-      isUsernameRequired
-    />
-  );
-}

packages/ui/src/mosaic/user-profile/__tests__/user-profile-edit-username.controller.test.ts

@@ -89,12 +89,9 @@ describe('userProfileEditUsernameMachine', () => {
     expect(saveUsername).not.toHaveBeenCalled();
   });
 
-  it('refuses to save an empty value where a username is required', () => {
+  it('refuses to save an empty value, since clearing a username is not on offer', () => {
     const saveUsername = vi.fn(() => Promise.resolve());
-    const actor = createActor(userProfileEditUsernameMachine, {
-      context: { saveUsername, savedUsername: 'prestonxyz', isRequired: true },
-    }).start();
-    actor.send({ type: 'OPEN' });
+    const actor = start(saveUsername);
     actor.send({ type: 'TYPE', value: '' });
 
     actor.send({ type: 'SAVE' });
@@ -161,25 +158,14 @@ describe('useUserProfileEditUsernameController', () => {
     expect(result.current.canSave).toBe(true);
   });
 
-  it('withholds the save on an empty value only where a username is required', () => {
-    const optional = renderHook(() =>
+  it('withholds the save on an empty value', () => {
+    const { result } = renderHook(() =>
       useUserProfileEditUsernameController({ username: 'prestonxyz', onSave: () => Promise.resolve() }),
     );
-    const required = renderHook(() =>
-      useUserProfileEditUsernameController({
-        username: 'prestonxyz',
-        isRequired: true,
-        onSave: () => Promise.resolve(),
-      }),
-    );
 
-    act(() => optional.result.current.onOpenChange(true));
-    act(() => optional.result.current.onUsernameChange(''));
-    act(() => required.result.current.onOpenChange(true));
-    act(() => required.result.current.onUsernameChange(''));
+    act(() => result.current.onOpenChange(true));
+    act(() => result.current.onUsernameChange(''));
 
-    // Clearing an optional username is a real edit; clearing a required one is not.
-    expect(optional.result.current.canSave).toBe(true);
-    expect(required.result.current.canSave).toBe(false);
+    expect(result.current.canSave).toBe(false);
   });
 });

packages/ui/src/mosaic/user-profile/user-profile-account-section.view.tsx

@@ -46,8 +46,6 @@ export interface UserProfileAccountSectionViewProps {
   hasImage?: boolean;
   name: string;
   username: string;
-  /** Whether the instance refuses an empty username. From `userSettings.attributes.username.required`. */
-  isUsernameRequired?: boolean;
   emails: UserProfileEmail[];
   phones: UserProfilePhone[];
   onProfilePictureChange?: (file: File) => void;
@@ -59,7 +57,6 @@ export interface UserProfileAccountSectionViewProps {
   onProfilePictureReject?: (rejections: FileRejection[]) => void;
   onRemoveProfilePicture?: () => void;
   onNameChange?: (value: string) => void;
-  /** Resolve to close the dialog; reject with an `Error` to keep it open showing why. Omit to hide the action. */
   onSaveUsername?: (username: string) => Promise<void>;
   onAddEmail?: () => void;
   onManageEmail?: (id: string) => void;
@@ -79,7 +76,6 @@ export function UserProfileAccountSectionView({
   hasImage = false,
   name,
   username,
-  isUsernameRequired,
   emails,
   phones,
   onProfilePictureChange,
@@ -179,7 +175,6 @@ export function UserProfileAccountSectionView({
               {onSaveUsername ? (
                 <Section.Actions>
                   <EditUsername
-                    isRequired={isUsernameRequired}
                     username={username}
                     onSave={onSaveUsername}
                   />
@@ -292,16 +287,8 @@ function ProfilePictureActions({
 }
 
 /** Split out so the controller is mounted only where the action exists. */
-function EditUsername({
-  isRequired,
-  username,
-  onSave,
-}: {
-  isRequired?: boolean;
-  username: string;
-  onSave: (username: string) => Promise<void>;
-}) {
-  const controller = useUserProfileEditUsernameController({ username, isRequired, onSave });
+function EditUsername({ username, onSave }: { username: string; onSave: (username: string) => Promise<void> }) {
+  const controller = useUserProfileEditUsernameController({ username, onSave });
 
   return (
     <UserProfileEditUsernameView

packages/ui/src/mosaic/user-profile/user-profile-edit-username.controller.ts

@@ -7,7 +7,6 @@ export interface UserProfileEditUsernameContext {
   saveUsername: (username: string) => Promise<void>;
   /** Injected every render. What `OPEN` seeds the field from. */
   savedUsername: string;
-  isRequired: boolean;
   username: string;
   error: UserProfileFormError<UserProfileEditUsernameField> | undefined;
 }
@@ -24,9 +23,9 @@ function notSeated(): Promise<never> {
   return Promise.reject(new Error('edit-username deps are not seated'));
 }
 
-/** The legacy form's two rules: nothing to save until the value moves, and no empty value where the instance requires one. */
+/** Clearing a username is not something the surface offers, so an empty value is never saveable. */
 function isSaveable(context: UserProfileEditUsernameContext): boolean {
-  return context.username !== context.savedUsername && !(context.isRequired && context.username === '');
+  return context.username !== context.savedUsername && context.username !== '';
 }
 
 type FieldCopy = UserProfileFormError<UserProfileEditUsernameField>['fields'];
@@ -44,7 +43,6 @@ export const userProfileEditUsernameMachine = createMachine({
   context: {
     saveUsername: notSeated,
     savedUsername: '',
-    isRequired: false,
     username: '',
     error: undefined,
   },
@@ -78,7 +76,6 @@ export const userProfileEditUsernameMachine = createMachine({
 
 export interface UserProfileEditUsernameControllerOptions {
   username?: string;
-  isRequired?: boolean;
   onSave: (username: string) => Promise<void>;
 }
 
@@ -95,11 +92,10 @@ export interface UserProfileEditUsernameController {
 
 export function useUserProfileEditUsernameController({
   username = '',
-  isRequired = false,
   onSave,
 }: UserProfileEditUsernameControllerOptions): UserProfileEditUsernameController {
   const [snapshot, send] = useMachine(userProfileEditUsernameMachine, {
-    context: { saveUsername: onSave, savedUsername: username, isRequired },
+    context: { saveUsername: onSave, savedUsername: username },
   });
 
   return {

packages/ui/src/mosaic/user-profile/user-profile-profile-panel.view.tsx

@@ -38,7 +38,6 @@ export function UserProfileProfilePanelView({
   hasImage,
   name = '',
   username = '',
-  isUsernameRequired,
   emails = [],
   phones = [],
   connectedAccounts = [],
@@ -76,7 +75,6 @@ export function UserProfileProfilePanelView({
           emails={emails}
           hasImage={hasImage}
           imageUrl={imageUrl}
-          isUsernameRequired={isUsernameRequired}
           name={name}
           phones={phones}
           username={username}