fix: say a message deleted elsewhere is gone instead of failing to load it

src/lib/__tests__/email-detail-cache.test.ts

@@ -1,4 +1,6 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
+import fs from 'node:fs';
+import path from 'node:path';
 
 vi.mock('../../api/jmap-client', () => ({
   jmapClient: { accountId: 'own', serverUrl: 'https://mail.example', username: 'me' },
@@ -15,7 +17,7 @@ import { getEmailFlags, getFullEmailsWithState, getThreadsHeaders } from '../../
 import { useOfflineCacheStore } from '../../stores/offline-cache-store';
 import { dispatchStateChange } from '../state-change-bus';
 import {
-  clearEmailDetailCache, loadDetail, loadDetails, loadThread, needsRevalidation, noteEmailState,
+  clearEmailDetailCache, EmailNotFoundError, loadDetail, loadDetails, loadThread, needsRevalidation, noteEmailState,
   patchDetail, peekDetail, peekRow, peekThread, prefetchMessage, rememberRows, subscribeEmailCache,
 } from '../email-detail-cache';
 
@@ -158,6 +160,31 @@ describe('loading a message', () => {
     expect(peekDetail('e1')).toBeUndefined();
   });
 
+  // A row deleted elsewhere opened "Failed to load email": the viewer could
+  // not tell a missing message from a failed load.
+  it('tells a message the server no longer has from a failed load', async () => {
+    fullGet.mockResolvedValueOnce(fullResponse([], 's1', ['e9']));
+    await expect(loadDetail('e9')).rejects.toBeInstanceOf(EmailNotFoundError);
+
+    fullGet.mockResolvedValueOnce(fullResponse([full('e1')], 's1'));
+    await loadDetail('e1');
+    noteEmailState(undefined, 's2');
+    flagsGet.mockResolvedValueOnce({ list: [], notFound: ['e1'], state: 's2' });
+    await expect(loadDetail('e1')).rejects.toBeInstanceOf(EmailNotFoundError);
+
+    fullGet.mockRejectedValueOnce(new TypeError('Network request failed'));
+    const failed = await loadDetail('e3').catch((err: unknown) => err);
+    expect(failed).not.toBeInstanceOf(EmailNotFoundError);
+  });
+
+  it('has the viewer say a gone message is no longer available and refresh the list', () => {
+    const viewer = fs.readFileSync(path.resolve(__dirname, '..', '..', 'screens/EmailThreadScreen.tsx'), 'utf8');
+    expect(viewer).toMatch(/if \(err instanceof EmailNotFoundError\) onGone\?\.\(\);/);
+    expect(viewer).toMatch(/const fetched = await ensureDetail\(activeEmailId, \(\) => \{ gone = true; \}\);/);
+    expect(viewer).toMatch(/t\('deep_link\.message_not_found', 'This message is no longer available\.'\)/);
+    expect(viewer).toMatch(/if \(gone\) void useEmailStore\.getState\(\)\.refreshEmails\(\);/);
+  });
+
   it('rejects with the fetch error when nothing is held', async () => {
     fullGet.mockRejectedValue(new Error('boom'));
     await expect(loadDetail('e1')).rejects.toThrow('boom');

src/lib/email-detail-cache.ts

@@ -177,6 +177,17 @@ function localSince(key: string, startedAt: number): FlagsHint | undefined {
   return local && local.at > startedAt ? local.patch : undefined;
 }
 
+/**
+ * The server has no such message (deleted or moved out of reach elsewhere),
+ * as opposed to a load that failed: the viewer says it is gone.
+ */
+export class EmailNotFoundError extends Error {
+  constructor(id: string) {
+    super(`Email ${id} not found`);
+    this.name = 'EmailNotFoundError';
+  }
+}
+
 /** The copy held for a message, if any. Synchronous: for rendering. */
 export function peekDetail(id: string, accountId?: string): Email | undefined {
   return details.get(keyOf(id, accountId))?.email;
@@ -292,7 +303,7 @@ async function fetchBodies(
     for (const id of ids) {
       const email = found.get(id);
       if (email) waiting.get(id)?.resolve(email);
-      else waiting.get(id)?.reject(new Error(`Email ${id} not found`));
+      else waiting.get(id)?.reject(new EmailNotFoundError(id));
     }
   } catch (err) {
     for (const id of ids) waiting.get(id)?.reject(err);
@@ -345,7 +356,7 @@ async function revalidate(
   for (const id of ids) {
     const email = peekDetail(id, accountId);
     if (email) waiting.get(id)?.resolve(email);
-    else waiting.get(id)?.reject(new Error(`Email ${id} not found`));
+    else waiting.get(id)?.reject(gone.has(id) ? new EmailNotFoundError(id) : new Error(`Email ${id} not found`));
   }
 }
 

src/screens/EmailThreadScreen.tsx

@@ -37,7 +37,7 @@ import {
 import { patchKeywordsForEmails } from '../api/email';
 import {
   loadDetail, loadDetails, loadThread, patchDetail, peekDetail, peekRow, peekThread, subscribeEmailCache,
-  type FlagsHint,
+  EmailNotFoundError, type FlagsHint,
 } from '../lib/email-detail-cache';
 import { shareEmailEml } from '../lib/email-export';
 import { useKeywordsStore, useAccountKeywordDefs, keywordToken, type KeywordDef } from '../stores/keywords-store';
@@ -237,9 +237,13 @@ function EmailViewer({ route, navigation, embedded = false, onActiveChange }: Pr
 
   // Cache first: a held copy renders at once and the promise resolves with the
   // checked one (which mark-as-read goes by). Concurrent loads share a request.
+  // `onGone` hears when the server has no such message any more.
   const ensureDetail = React.useCallback(
-    (id: string): Promise<Email | null> =>
-      loadDetail(id, ownerAccountId, hintFor(id)).catch(() => peekDetail(id, ownerAccountId) ?? null),
+    (id: string, onGone?: () => void): Promise<Email | null> =>
+      loadDetail(id, ownerAccountId, hintFor(id)).catch((err) => {
+        if (err instanceof EmailNotFoundError) onGone?.();
+        return peekDetail(id, ownerAccountId) ?? null;
+      }),
     [ownerAccountId, hintFor],
   );
   const ensureDetails = React.useCallback((ids: string[]) => {
@@ -418,10 +422,18 @@ function EmailViewer({ route, navigation, embedded = false, onActiveChange }: Pr
     // this lands. Then mark it read per the user's delay.
     setError(null);
     void (async () => {
-      const fetched = await ensureDetail(activeEmailId);
+      let gone = false;
+      const fetched = await ensureDetail(activeEmailId, () => { gone = true; });
       if (cancelled) return;
       if (!fetched) {
-        if (!detailOf(activeEmailId)) setError(t('email_viewer.load_failed', 'Failed to load email'));
+        if (!detailOf(activeEmailId)) {
+          // Deleted or moved elsewhere: say so (webmail deep_link
+          // message_not_found) and let the list drop its row.
+          setError(gone
+            ? t('deep_link.message_not_found', 'This message is no longer available.')
+            : t('email_viewer.load_failed', 'Failed to load email'));
+          if (gone) void useEmailStore.getState().refreshEmails();
+        }
         return;
       }
       cancelRead = scheduleMarkRead(fetched);