chore(rln): return empty metadata if it doesnt exist (#230)

* chore(rln): return empty metadata if it doesnt exist

* fix: clippy

rln/src/circuit.rs

@@ -77,7 +77,7 @@ pub fn zkey_from_folder(
 }
 
 // Loads the verification key from a bytes vector
-pub fn vk_from_raw(vk_data: &Vec<u8>, zkey_data: &Vec<u8>) -> Result<VerifyingKey<Curve>> {
+pub fn vk_from_raw(vk_data: &[u8], zkey_data: &Vec<u8>) -> Result<VerifyingKey<Curve>> {
     let verifying_key: VerifyingKey<Curve>;
 
     if !vk_data.is_empty() {

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_api_tests.rs

@@ -977,7 +977,7 @@ fn test_get_leaf() {
 }
 
 #[test]
-fn test_metadata() {
+fn test_valid_metadata() {
     let tree_height = TEST_TREE_HEIGHT;
 
     let input_buffer =
@@ -993,3 +993,18 @@ fn test_metadata() {
 
     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

@@ -341,7 +341,6 @@ mod test {
     fn test_merkle_proof_ffi() {
         let tree_height = TEST_TREE_HEIGHT;
         let leaf_index = 3;
-        let user_message_limit = 1;
 
         // We create a RLN instance
         let mut rln_pointer = MaybeUninit::<*mut RLN>::uninit();
@@ -671,7 +670,7 @@ mod test {
     fn test_rln_proof_ffi() {
         let tree_height = TEST_TREE_HEIGHT;
         let no_of_leaves = 256;
-        let user_message_limit = Fr::from(65535);
+        let user_message_limit = Fr::from(100);
 
         // We generate a vector of random leaves
         let mut leaves: Vec<Fr> = Vec::new();
@@ -704,7 +703,6 @@ mod test {
         let result_data = <&[u8]>::from(&output_buffer).to_vec();
         let (identity_secret_hash, read) = bytes_le_to_fr(&result_data);
         let (id_commitment, _) = bytes_le_to_fr(&result_data[read..].to_vec());
-        let rate_commitment = utils_poseidon_hash(&[id_commitment, user_message_limit]);
 
         let identity_index: usize = no_of_leaves;
 
@@ -717,7 +715,6 @@ mod test {
         let rln_identifier = hash_to_field(b"test-rln-identifier");
         let external_nullifier = utils_poseidon_hash(&[epoch, rln_identifier]);
 
-        let user_message_limit = Fr::from(100);
         let message_id = Fr::from(0);
         let rate_commitment = utils_poseidon_hash(&[id_commitment, user_message_limit]);
 
@@ -727,9 +724,6 @@ mod test {
         let success = set_next_leaf(rln_pointer, input_buffer);
         assert!(success, "set next leaf call failed");
 
-        // We generate a random rln_identifier
-        let rln_identifier = hash_to_field(b"test-rln-identifier");
-
         // We prepare input for generate_rln_proof API
         // input_data is [ identity_secret<32> | id_index<8> | user_message_limit<32> | message_id<32> | external_nullifier<32> | signal_len<8> | signal<var> ]
         let mut serialized: Vec<u8> = Vec::new();
@@ -819,7 +813,6 @@ mod test {
         let message_id = Fr::from(0);
 
         // We set as leaf rate_commitment, its index would be equal to no_of_leaves
-        let rate_commitment = utils_poseidon_hash(&[id_commitment, user_message_limit]);
         let leaf_ser = fr_to_bytes_le(&rate_commitment);
         let input_buffer = &Buffer::from(leaf_ser.as_ref());
         let success = set_next_leaf(rln_pointer, input_buffer);
@@ -1268,7 +1261,7 @@ mod test {
     }
 
     #[test]
-    fn test_metadata() {
+    fn test_valid_metadata() {
         // We create a RLN instance
         let tree_height = TEST_TREE_HEIGHT;
 
@@ -1294,4 +1287,25 @@ 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);
+    }
 }