Fix JSON-RPC request parsing errors being ignored

light-base/src/json_rpc_service/background.rs

@@ -704,16 +704,36 @@ pub(super) async fn run<TPlat: PlatformRef>(
 
             WakeUpReason::IncomingJsonRpcRequest(request_json) => {
                 // New JSON-RPC request pulled from the channel.
-                let Ok((request_id_json, request_parsed)) =
-                    methods::parse_jsonrpc_client_to_server(&request_json)
-                else {
-                    // Request has failed to parse. Immediately return an answer.
-                    let _ = me
-                        .responses_tx
-                        .send(parse::build_parse_error_response())
-                        .await;
-                    continue;
-                };
+
+                let (request_id_json, request_parsed) =
+                    match methods::parse_jsonrpc_client_to_server(&request_json) {
+                        Ok(r) => r,
+                        Err(methods::ParseClientToServerError::JsonRpcParse(_)) => {
+                            // Request has failed to parse. Immediately return an answer.
+                            let _ = me
+                                .responses_tx
+                                .send(parse::build_parse_error_response())
+                                .await;
+                            continue;
+                        }
+                        Err(methods::ParseClientToServerError::Method { request_id, error }) => {
+                            // Invalid method or parameters. Immediately return an answer.
+                            let _ = me.responses_tx.send(error.to_json_error(request_id)).await;
+                            continue;
+                        }
+                        Err(methods::ParseClientToServerError::UnknownNotification { .. }) => {
+                            // Invalid method. Immediately return an answer.
+                            let _ = me
+                                .responses_tx
+                                .send(parse::build_error_response(
+                                    "null",
+                                    parse::ErrorResponse::InvalidRequest,
+                                    None,
+                                ))
+                                .await;
+                            continue;
+                        }
+                    };
 
                 // Print a warning for legacy JSON-RPC API functions.
                 match request_parsed {

wasm-node/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Fixed
+
+- A "parse error" JSON-RPC response is no longer erroneously sent back in case of an unrecognized JSON-RPC function name or wrong parameter types. ([#2138](https://github.com/smol-dot/smoldot/pull/2138))
+
 ## 2.0.35 - 2025-05-27
 
 ### Changed

wasm-node/javascript/test/misc.mjs

@@ -40,14 +40,33 @@ test('malformed JSON-RPC request generates an error', async t => {
     .then(() => client.terminate());
 });
 
+test('invalid JSON-RPC method generates an error', async t => {
+  const client = start({ logCallback: () => { } });
+  await client
+    .addChain({ chainSpec: westendSpec })
+    .then((chain) => {
+      chain.sendJsonRpc('{"jsonrpc":"2.0","id":1,"method":"this method doesnt exist","params":[]}');
+      return chain;
+    })
+    .then(async (chain) => {
+      const response = await chain.nextJsonRpcResponse();
+      const parsed = JSON.parse(response);
+      if (parsed.id === null && parsed.error)
+        t.pass();
+      else
+        t.fail(response);
+    })
+    .then(() => client.terminate());
+});
+
 test('disableJsonRpc option forbids sendJsonRpc', async t => {
   const client = start({ logCallback: () => { } });
   await client
     .addChain({ chainSpec: westendSpec, disableJsonRpc: true })
     .then((chain) => {
       try {
         chain.sendJsonRpc('{"jsonrpc":"2.0","id":1,"method":"system_name","params":[]}');
-      } catch(error) {
+      } catch (error) {
         t.assert(error instanceof JsonRpcDisabledError);
         t.pass();
       }
@@ -62,7 +81,7 @@ test('disableJsonRpc option forbids nextJsonRpcResponse', async t => {
     .then(async (chain) => {
       try {
         await chain.nextJsonRpcResponse();
-      } catch(error) {
+      } catch (error) {
         t.assert(error instanceof JsonRpcDisabledError);
         t.pass();
       }