fix(core): a folder listed just as its create lands is listed from the database (B177)

crates/pdfs-core/src/db/nodes.rs

@@ -533,9 +533,10 @@ impl Db {
     /// re-enumerates from the remote on next access.
     pub fn set_listed(&self, uid: &NodeUid, listed: bool) -> Result<()> {
         let conn = self.conn.lock();
+        let (key, uid) = row_key(&uid.to_string());
         conn.execute(
-            "UPDATE nodes SET listed = ?2 WHERE uid = ?1",
+            &format!("UPDATE nodes SET listed = ?2 WHERE {key} = ?1"),
-            params![uid.to_string(), listed as i64],
+            params![uid, listed as i64],
         )?;
         Ok(())
     }
@@ -694,10 +695,11 @@ impl Db {
     /// server head, so changes made while unmounted are still applied (P2).
     pub fn children_if_listed(&self, parent: &NodeUid) -> Result<Option<Vec<Node>>> {
         let conn = self.read();
+        let (key, folder) = row_key(&parent.to_string());
         let listed: Option<i64> = conn
             .query_row(
-                "SELECT listed FROM nodes WHERE uid = ?1",
+                &format!("SELECT listed FROM nodes WHERE {key} = ?1"),
-                params![parent.to_string()],
+                params![folder],
                 |r| r.get(0),
             )
             .optional()?;
@@ -792,6 +794,17 @@ pub(super) fn node_lid(conn: &rusqlite::Connection, uid: &str) -> Result<Option<
     Ok(row.optional()?)
 }
 
+/// The column and value that find `uid`'s own row. A stand-in is found by its
+/// local id: a create that lands gives the row the uid Drive made before the
+/// tree has it, and the tree asks by the stand-in until then (`docs/BUGS.md`
+/// B177).
+fn row_key(uid: &str) -> (&'static str, Value) {
+    match local_lid(uid) {
+        Some(lid) => ("lid", Value::Integer(lid)),
+        None => ("uid", Value::Text(uid.to_owned())),
+    }
+}
+
 /// The column and value a row names `parent` by: its local id when it has a
 /// row, which the children keep when it lands, or its uid when it has none,
 /// as a device folder's root does.

crates/pdfs-core/src/db/tests.rs

@@ -3282,6 +3282,37 @@ fn a_stand_in_keeps_its_access_once_its_create_has_landed() {
     );
 }
 
+#[test]
+fn a_stand_in_folder_stays_listed_once_its_create_has_landed() {
+    let db = Db::open_in_memory().unwrap();
+    db.upsert_node(&folder("parent", None, "My Files")).unwrap();
+    let parent = uid("parent").to_string();
+    let lid = db.add_local_row(&parent, "dir", true, 1).unwrap();
+    let local = local_uid(lid);
+    let stand_in = NodeUid::new(VolumeId::from("local"), LinkId::from(lid.to_string()));
+    let mut node = folder("new", Some("parent"), "dir");
+    node.uid = stand_in.clone();
+    db.upsert_node(&node).unwrap();
+    db.set_listed(&stand_in, true).unwrap();
+    let real = uid("real").to_string();
+    let (id, _) = db
+        .enqueue_op(&op_on(OP_MKDIR, &local, Some(&parent)))
+        .unwrap();
+    db.claim_next_due_op(1).unwrap().unwrap();
+    db.finish_create(id, None, &landing(&local, &real, &parent, "dir"), |_| None)
+        .unwrap();
+
+    // The tree still names the folder by its stand-in for a moment; a listing
+    // asked by it must not go to Drive, which has never heard of it.
+    assert!(
+        db.children_if_listed(&stand_in)
+            .unwrap()
+            .is_some_and(|kids| kids.is_empty())
+    );
+    db.set_listed(&stand_in, false).unwrap();
+    assert!(db.children_if_listed(&uid("real")).unwrap().is_none());
+}
+
 #[test]
 fn a_node_queued_under_both_its_uids_is_sent_one_op_at_a_time() {
     let db = Db::open_in_memory().unwrap();

docs/BUGS.md

@@ -12,6 +12,28 @@ Conventions:
 
 ---
 
+## B177 — A folder listed just as its create lands answers "Input/output error"
+
+**Status:** Fixed (unverified).
+**Found:** 2026-10-04, by the account run on 378667f, on an on-demand sync folder: B100's
+`lstat` of `b100-copy/dir-0/sub-0/file-00.bin` failed with `EIO`. The daemon logged
+`enumerate folder children failed folder_uid=local~163903 ... InvalidEncryptedIdFormat` 85 ms
+before `dir-0`'s create landed.
+
+**Where:** `Db::children_if_listed` and `Db::set_listed` in `crates/pdfs-core/src/db/nodes.rs`.
+
+**Cause.** A folder made on the mount is marked as listed, so its listing comes from the
+database and never from Drive, which has not heard of it. The flag was looked up by uid. In
+B173's gap the row already has the uid Drive gave the folder and the tree still asks by the
+stand-in, so the lookup found no row, and the listing went to Drive with the stand-in.
+
+**Fix.** A stand-in finds its row by its local id, before and after its create lands.
+
+**Test:** `a_stand_in_folder_stays_listed_once_its_create_has_landed` in
+`crates/pdfs-core/src/db/tests.rs`.
+
+---
+
 ## B176 — A write closed just as its file's create lands is dropped
 
 **Status:** Fixed (unverified).

docs/CHANGELOG.md

@@ -79,6 +79,8 @@ by its local id, in the queue, the stored tree and pins alike.
 - **A file replaced by a rename just as it reached Drive is removed from Drive too.** It no
   longer stayed there, and the next rename of its name no longer moved it instead (B175).
 - **A write closed just as its file reached Drive is no longer lost** (B176).
+- **Opening a folder just as it reaches Drive no longer fails with "Input/output error"**
+  (B177).
 - **A file renamed just as its upload finished keeps its new name.** The mount no longer showed
   the old name, and a second rename no longer failed with "No such file or directory" (B152,
   B172).

docs/MILESTONE-3.0.0-STATUS.md

@@ -9,7 +9,7 @@ Tracks `docs/MILESTONE-3.0.0.md`. Update it with every commit that moves a phase
 - **Phase 2**: local ids, inode = local id, one tree for every mount (2.10.0).
 - **Phase 3, first part**: mkdir, create, rename, unlink and rmdir on the mount are recorded
   locally and sent from the queue; `"local_first": false` brings back the old path (5e0f30c).
-- Fixes from the simulation and account runs since then: B127 and B141 to B176.
+- Fixes from the simulation and account runs since then: B127 and B141 to B177.
 - **Sync issues, first cut** (§6.2): refusals sorted into issues, shown at once in the app,
   tray and CLI; Export button and `pdfs sync export`; `pdfs sync issues`.
 
@@ -121,6 +121,8 @@ Tracks `docs/MILESTONE-3.0.0.md`. Update it with every commit that moves a phase
          in the same gap was refused with `EACCES` (B174, fixed). The loop on 378667f failed
          seed 8: a file replaced by a rename in that gap stayed on Drive (B175, fixed), and
          seed 12: a write closed as its file's create landed was dropped (B176, fixed).
+         The account run on 378667f: a folder listed as its create landed asked Drive by
+         its stand-in and answered `EIO` (B177, fixed).
 5. **Release**: 2.10.0 is tagged; the 2.9.0 tag still waits for the user's go-ahead.
 
 ## After 3.0.0