feat(rln-v1): return empty metadata if it doesnt exist (#231)

rln/src/pm_tree_adapter.rs

@@ -246,7 +246,8 @@ impl ZerokitMerkleTree for PmTree {
         let data = self.tree.db.get(METADATA_KEY)?;
 
         if data.is_none() {
-            return Err(Report::msg("metadata does not exist"));
+            // send empty Metadata
+            return Ok(Vec::new());
         }
         Ok(data.unwrap())
     }

rln/src/public.rs

@@ -2108,4 +2108,19 @@ mod test {
 
         assert_eq!(arbitrary_metadata, received_metadata);
     }
+
+    #[test]
+    fn test_empty_metadata() {
+        let tree_height = TEST_TREE_HEIGHT;
+
+        let input_buffer =
+            Cursor::new(json!({ "resources_folder": TEST_RESOURCES_FOLDER }).to_string());
+        let rln = RLN::new(tree_height, input_buffer).unwrap();
+
+        let mut buffer = Cursor::new(Vec::<u8>::new());
+        rln.get_metadata(&mut buffer).unwrap();
+        let received_metadata = buffer.into_inner();
+
+        assert_eq!(received_metadata.len(), 0);
+    }
 }

rln/tests/ffi.rs

@@ -1209,7 +1209,7 @@ mod test {
     }
 
     #[test]
-    fn test_metadata() {
+    fn test_valid_metadata() {
         // We create a RLN instance
         let tree_height = TEST_TREE_HEIGHT;
 
@@ -1235,4 +1235,25 @@ mod test {
 
         assert_eq!(result_data, seed_bytes.to_vec());
     }
+
+    #[test]
+    fn test_empty_metadata() {
+        // We create a RLN instance
+        let tree_height = TEST_TREE_HEIGHT;
+
+        let mut rln_pointer = MaybeUninit::<*mut RLN>::uninit();
+        let input_config = json!({ "resources_folder": TEST_RESOURCES_FOLDER }).to_string();
+        let input_buffer = &Buffer::from(input_config.as_bytes());
+        let success = new(tree_height, input_buffer, rln_pointer.as_mut_ptr());
+        assert!(success, "RLN object creation failed");
+        let rln_pointer = unsafe { &mut *rln_pointer.assume_init() };
+
+        let mut output_buffer = MaybeUninit::<Buffer>::uninit();
+        let success = get_metadata(rln_pointer, output_buffer.as_mut_ptr());
+        assert!(success, "get_metadata call failed");
+
+        let output_buffer = unsafe { output_buffer.assume_init() };
+
+        assert_eq!(output_buffer.len, 0);
+    }
 }