fix: let the composer send and save again in the account it was opened in

locales/rn/en.json

@@ -299,6 +299,7 @@
     "identity_unavailable": "Identity unavailable",
     "image_load_failed": "Could not load image",
     "login_switched_body": "You started this message in {account}. Switch back to that account to send it.",
+    "login_switched_save_body": "You started this message in {account}. Switch back to that account to save it.",
     "login_switched_title": "Account switched",
     "no_recipient": "(no recipient)",
     "no_sent_folder": "No Sent folder found",

src/lib/__tests__/draft-login.test.ts

@@ -1,20 +1,34 @@
 import { describe, it, expect } from 'vitest';
-import { composerLoginMoved } from '../draft-login';
+import { composerLoginMoved, servedLoginOf } from '../draft-login';
+import { generateAccountId } from '../account-utils';
+
+// Real formats: the registry names logins `username@host`, the session names
+// JMAP accounts with short ids that never equal a registry id.
+const A = generateAccountId('usera@example.org', 'https://mail.example.org');
+const B = generateAccountId('userb@example.org', 'https://other.example.net');
+const client = (username: string, serverUrl: string, isConnected = true) => ({ username, serverUrl, isConnected });
+
+describe('servedLoginOf', () => {
+  it('names the login a client serves by its registry id, not its JMAP account id', () => {
+    expect(servedLoginOf(client('usera@example.org', 'https://mail.example.org'))).toBe(A);
+    expect(servedLoginOf(client('usera@example.org', 'https://mail.example.org', false))).toBeNull();
+  });
+});
 
 describe('composerLoginMoved', () => {
   it('stays put while the login the composer opened in is active', () => {
-    expect(composerLoginMoved('acc-a', { activeAccountId: 'acc-a', connectedAccountId: 'acc-a' })).toBe(false);
+    expect(composerLoginMoved(A, { activeAccountId: A, servedLogin: servedLoginOf(client('usera@example.org', 'https://mail.example.org')) })).toBe(false);
     // Offline cold start: the client is not connected yet.
-    expect(composerLoginMoved('acc-a', { activeAccountId: 'acc-a', connectedAccountId: null })).toBe(false);
+    expect(composerLoginMoved(A, { activeAccountId: A, servedLogin: null })).toBe(false);
   });
 
   it('moves once another login is active or the client serves another one', () => {
-    expect(composerLoginMoved('acc-a', { activeAccountId: 'acc-b', connectedAccountId: 'acc-b' })).toBe(true);
+    expect(composerLoginMoved(A, { activeAccountId: B, servedLogin: B })).toBe(true);
     // Mid-switch: the registry still names A, the client already serves B.
-    expect(composerLoginMoved('acc-a', { activeAccountId: 'acc-a', connectedAccountId: 'acc-b' })).toBe(true);
+    expect(composerLoginMoved(A, { activeAccountId: A, servedLogin: servedLoginOf(client('userb@example.org', 'https://other.example.net')) })).toBe(true);
   });
 
   it('never blocks a composer opened without a login', () => {
-    expect(composerLoginMoved(null, { activeAccountId: 'acc-b', connectedAccountId: 'acc-b' })).toBe(false);
+    expect(composerLoginMoved(null, { activeAccountId: B, servedLogin: B })).toBe(false);
   });
 });

src/lib/draft-login.ts

@@ -6,12 +6,24 @@
 // login, where the same ids name other messages: an autosave or a discard
 // destroyed one of them (webmail 54b197080, d72bff95f). So the composer
 // remembers the login it was opened in and writes nothing once that changed.
+//
+// Logins are registry ids (`username@host`, lib/account-utils). The JMAP
+// account id the session names ('b', 'c', ...) is another thing: it repeats
+// across servers and never equals a registry id.
+
+import { generateAccountId } from './account-utils';
 
 export interface ComposerLogins {
   /** The registry's active account now. */
   activeAccountId: string | null;
-  /** The account the JMAP client is connected to now; null while it is not connected. */
-  connectedAccountId: string | null;
+  /** The login (registry id) the JMAP client serves now; null while it is not connected. */
+  servedLogin: string | null;
+}
+
+/** The registry id of the login a client serves, or null while it serves none. */
+export function servedLoginOf(client: { isConnected: boolean; username: string | null; serverUrl: string | null }): string | null {
+  if (!client.isConnected || !client.username || !client.serverUrl) return null;
+  return generateAccountId(client.username, client.serverUrl);
 }
 
 /**
@@ -22,5 +34,5 @@ export interface ComposerLogins {
 export function composerLoginMoved(owner: string | null | undefined, now: ComposerLogins): boolean {
   if (!owner) return false;
   if (now.activeAccountId !== owner) return true;
-  return now.connectedAccountId != null && now.connectedAccountId !== owner;
+  return now.servedLogin != null && now.servedLogin !== owner;
 }

src/screens/ComposeScreen.tsx

@@ -66,7 +66,7 @@ import {
   findComposeIdentityId, findDraftIdentityId, resolveComposeAccountEmail, resolveReplyIdentity,
 } from '../lib/reply-identity';
 import { shouldBlockEditorRemoteImages } from '../lib/editor-html';
-import { composerLoginMoved } from '../lib/draft-login';
+import { composerLoginMoved, servedLoginOf } from '../lib/draft-login';
 import {
   initialDraftPartBlobState, liveBlobId, rebaseDraftPartBlobs, withSnapshotBody,
 } from '../lib/draft-part-blobs';
@@ -1127,7 +1127,7 @@ export default function ComposeScreen({ route, navigation }: Props) {
   const ownerLoginRef = React.useRef(useAccountStore.getState().activeAccountId);
   const loginMoved = () => composerLoginMoved(ownerLoginRef.current, {
     activeAccountId: useAccountStore.getState().activeAccountId,
-    connectedAccountId: jmapClient.connectedAccountId,
+    servedLogin: servedLoginOf(jmapClient),
   });
   const [draftStatus, setDraftStatus] = React.useState<'idle' | 'saving' | 'saved' | 'failed'>('idle');
   const [savingDraft, setSavingDraft] = React.useState(false);
@@ -1443,6 +1443,20 @@ export default function ComposeScreen({ route, navigation }: Props) {
       Alert.alert(t('email_composer.save_failed', 'Failed to save'), draftUnsavableReason);
       return;
     }
+    // Another login is active: saving writes nothing (saveDraftOnce), so
+    // closing now would drop the text as if it had been saved.
+    if (loginMoved()) {
+      const owner = ownerLoginRef.current ? useAccountStore.getState().getAccountById(ownerLoginRef.current) : undefined;
+      Alert.alert(
+        t('email_composer.login_switched_title', 'Account switched'),
+        t(
+          'email_composer.login_switched_save_body',
+          'You started this message in {account}. Switch back to that account to save it.',
+          { account: owner?.email || owner?.displayName || '' },
+        ),
+      );
+      return;
+    }
     setSavingDraft(true);
     try {
       await saveDraft({ live: true });