fix(rustdb-storage): return empty collection list for missing databases

rust/crates/rustdb-storage/src/file.rs

@@ -473,7 +473,7 @@ impl FileStorageAdapter {
     fn list_collection_dirs(&self, db: &str) -> StorageResult<Vec<String>> {
         let db_dir = self.db_dir(db);
         if !db_dir.exists() {
-            return Err(StorageError::NotFound(format!("database '{db}'")));
+            return Ok(Vec::new());
         }
         let mut colls = Vec::new();
         let entries = std::fs::read_dir(&db_dir)?;

rust/crates/rustdb-storage/src/memory.rs

@@ -129,10 +129,9 @@ impl StorageAdapter for MemoryStorageAdapter {
     // ---- collection ----
 
     async fn list_collections(&self, db: &str) -> StorageResult<Vec<String>> {
-        let db_ref = self
-            .data
-            .get(db)
-            .ok_or_else(|| StorageError::NotFound(format!("database '{db}'")))?;
+        let Some(db_ref) = self.data.get(db) else {
+            return Ok(Vec::new());
+        };
         Ok(db_ref.iter().map(|e| e.key().clone()).collect())
     }