fix: folders containing a system folder name disappear from the sidebar #771

lib/__tests__/mailbox-deep-nesting.test.ts

@@ -349,7 +349,7 @@ describe('GitHub #118: duplicate subfolder names cause depth-4 orphaning', () =>
     const mailboxes = [
       makeMailbox({ id: 'inbox', name: 'Inbox', role: 'inbox' }),
       makeMailbox({ id: 'sent-role', name: 'Sent', role: 'sent' }),
-      makeMailbox({ id: 'sent-dup', name: 'Sent Mail' }), // root-level duplicate - OK to remove
+      makeMailbox({ id: 'sent-dup', name: 'Sent Mail' }), // root-level, name only *contains* "Sent" - must keep (#771)
       makeMailbox({ id: 'proj', name: 'Projects', parentId: 'inbox' }),
       makeMailbox({ id: 'sent-nested', name: 'Sent', parentId: 'proj' }), // nested - must keep
       makeMailbox({ id: 'report', name: 'Report', parentId: 'sent-nested' }),
@@ -358,8 +358,10 @@ describe('GitHub #118: duplicate subfolder names cause depth-4 orphaning', () =>
     const tree = buildMailboxTree(mailboxes);
     const flat = flattenMailboxTree(tree);
 
-    // "Sent Mail" at root (no parentId) can be deduped - that's fine
-    // But "Sent" nested under Projects must be kept
+    // "Sent Mail" at root is a distinct folder, not a duplicate of role "Sent"
+    expect(flat.find(n => n.id === 'sent-dup')).toBeDefined();
+
+    // "Sent" nested under Projects must be kept
     const sentNested = flat.find(n => n.id === 'sent-nested');
     expect(sentNested).toBeDefined();
     expect(sentNested!.depth).toBe(2);
@@ -370,6 +372,69 @@ describe('GitHub #118: duplicate subfolder names cause depth-4 orphaning', () =>
   });
 });
 
+describe('GitHub #771: folders whose name contains a role folder name disappear', () => {
+  it('keeps root-level folders that merely contain a role folder name', () => {
+    const mailboxes = [
+      makeMailbox({ id: 'inbox', name: 'Inbox', role: 'inbox' }),
+      makeMailbox({ id: 'archive-role', name: 'Archive', role: 'archive' }),
+      makeMailbox({ id: 'sent-role', name: 'Sent', role: 'sent' }),
+      makeMailbox({ id: 'trash-role', name: 'Trash', role: 'trash' }),
+      makeMailbox({ id: 'old-inbox', name: 'old inbox' }),
+      makeMailbox({ id: 'archive-2025', name: '2025 Archive' }),
+      makeMailbox({ id: 'sent-acct', name: 'Sent to Accounting' }),
+      makeMailbox({ id: 'trashy', name: 'Trashy Podcasts' }),
+    ];
+
+    const rootIds = buildMailboxTree(mailboxes).map(n => n.id);
+
+    expect(rootIds).toContain('old-inbox');
+    expect(rootIds).toContain('archive-2025');
+    expect(rootIds).toContain('sent-acct');
+    expect(rootIds).toContain('trashy');
+  });
+
+  it('keeps short root-level folders that are a substring of a role folder name', () => {
+    // The old bidirectional match also ate folders *shorter* than the role name.
+    const mailboxes = [
+      makeMailbox({ id: 'inbox', name: 'Inbox', role: 'inbox' }),
+      makeMailbox({ id: 'drafts-role', name: 'Drafts', role: 'drafts' }),
+      makeMailbox({ id: 'in', name: 'In' }),
+      makeMailbox({ id: 'draft', name: 'Draft' }),
+    ];
+
+    const rootIds = buildMailboxTree(mailboxes).map(n => n.id);
+
+    expect(rootIds).toContain('in');
+    expect(rootIds).toContain('draft');
+  });
+
+  it('still drops a root-level folder whose name exactly matches a role folder', () => {
+    const mailboxes = [
+      makeMailbox({ id: 'inbox', name: 'Inbox', role: 'inbox' }),
+      makeMailbox({ id: 'archive-role', name: 'Archive', role: 'archive' }),
+      makeMailbox({ id: 'archive-dup', name: 'archive' }),
+    ];
+
+    const rootIds = buildMailboxTree(mailboxes).map(n => n.id);
+
+    expect(rootIds).toContain('archive-role');
+    expect(rootIds).not.toContain('archive-dup');
+  });
+
+  it('scopes exact-name deduplication to the same account', () => {
+    const mailboxes = [
+      makeMailbox({ id: 'inbox-a', name: 'Inbox', role: 'inbox', accountId: 'a' }),
+      makeMailbox({ id: 'archive-a', name: 'Archive', role: 'archive', accountId: 'a' }),
+      // Same name, different account - not a duplicate
+      makeMailbox({ id: 'archive-b', name: 'Archive', accountId: 'b' }),
+    ];
+
+    const rootIds = buildMailboxTree(mailboxes).map(n => n.id);
+
+    expect(rootIds).toContain('archive-b');
+  });
+});
+
 describe('mailbox orphan behavior (missing parent)', () => {
   it('should expose orphan-to-root behavior when parent is missing', () => {
     // Simulates what happens if JMAP response is incomplete (e.g., truncated at 500 objects)

lib/utils.ts

@@ -292,12 +292,12 @@ function deduplicateMailboxes(mailboxes: Mailbox[]): Mailbox[] {
     // Check if this root-level mailbox is a duplicate of a role-based mailbox in the SAME account
     const accountKey = mb.accountId || '';
     const accountRoles = rolesByAccount.get(accountKey) || [];
-    const lowerName = mb.name.toLowerCase();
-    const matchedRole = accountRoles.find(roleMb => {
-      const roleLowerName = roleMb.name.toLowerCase();
-      // Check for common duplicates: "Sent Mail" vs "Sent", etc.
-      return lowerName.includes(roleLowerName) || roleLowerName.includes(lowerName);
-    });
+    // Only an exact name collision counts as a duplicate. Substring matching
+    // silently hid legitimate user folders whose name merely contained a role
+    // folder's name - "Old Inbox", "2025 Archive", "Sent to Accounting".
+    // (GitHub #771)
+    const lowerName = mb.name.trim().toLowerCase();
+    const matchedRole = accountRoles.find(roleMb => roleMb.name.trim().toLowerCase() === lowerName);
     const isDuplicate = !!matchedRole;
 
     // Only keep if not a duplicate