Fsync the parent directory after compact rename

src/artifact.rs

@@ -360,7 +360,7 @@ pub(crate) fn hash_payload(root: &Path) -> Result<Vec<ArtifactFile>, SnapshotErr
     Ok(files)
 }
 
-fn fsync_dir(path: &Path) -> Result<(), SnapshotError> {
+pub(crate) fn fsync_dir(path: &Path) -> Result<(), SnapshotError> {
     File::open(path)?.sync_all()?;
     Ok(())
 }

src/snapshot.rs

@@ -1119,6 +1119,10 @@ fn compact_to_file(
 
     tmp.as_file().sync_all()?;
     tmp.persist(path).map_err(|e| SnapshotError::Io(e.error))?;
+    // persist() is rename(2). The inode is durable; the directory entry is
+    // not until the parent is fsynced. artifact::rename_into_place already
+    // does this — compact is the fold's only other rename-publish.
+    crate::artifact::fsync_dir(dir)?;
 
     Ok(())
 }
@@ -1630,4 +1634,27 @@ mod tests {
         );
         assert_eq!(snap.entries["node.a"].value, b"survives");
     }
+
+    /// Compact is the fold's durable publish: inode `sync_all` then rename.
+    /// Without a parent-directory fsync the new dirent can vanish on power
+    /// loss — the same hole `artifact::rename_into_place` already closes.
+    #[test]
+    fn compact_to_file_fsyncs_parent_dirent() {
+        let src = include_str!("snapshot.rs");
+        let compact = src
+            .split("fn compact_to_file(")
+            .nth(1)
+            .expect("compact_to_file must exist");
+        let compact = compact
+            .split(
+                "\n// ---------------------------------------------------------------------------",
+            )
+            .next()
+            .unwrap();
+        assert!(
+            compact.contains("fsync_dir"),
+            "compact_to_file must fsync the parent directory after persist, \
+             matching artifact::rename_into_place (Pedra F17)"
+        );
+    }
 }