fix(rpc): Fixes getNodeInfo serialisation (#1991)

When calling the RPC server across HTTP, the automagical json-rpc-server
serialisation was failing to deserialise the `NodeInfo`. The constructor
of the NodeInfo object was not exactly `Object`, so the converter did
not go recursively into each field.

This PR makes the check for "is something an object" wider, and changes
the RPC server test so it reproduces the issue without the fix. Before
this change, `getNodeInfo().rollupAddress` was equal to `{ type:
'EthAddress', data: '0x...' }`, so calling `toString()` on it resulted
in the string `[object Object]`.

yarn-project/aztec-rpc/src/aztec_rpc_server/test/aztec_rpc_test_suite.ts

@@ -132,9 +132,9 @@ export const aztecRpcTestSuite = (testName: string, aztecRpcSetup: () => Promise
 
     it('successfully gets node info', async () => {
       const nodeInfo = await rpc.getNodeInfo();
-      expect(nodeInfo.version).toBeDefined();
-      expect(nodeInfo.chainId).toBeDefined();
-      expect(nodeInfo.rollupAddress).toBeDefined();
+      expect(typeof nodeInfo.version).toEqual('number');
+      expect(typeof nodeInfo.chainId).toEqual('number');
+      expect(nodeInfo.rollupAddress.toString()).toMatch(/0x[a-fA-F0-9]+/);
     });
 
     // Note: Not testing `isGlobalStateSynchronised`, `isAccountStateSynchronised` and `getSyncStatus` as these methods

yarn-project/foundation/src/json-rpc/convert.ts

@@ -96,8 +96,9 @@ export function convertFromJsonObj(cc: ClassConverter, obj: any): any {
   if (Array.isArray(obj)) {
     return obj.map((x: any) => convertFromJsonObj(cc, x));
   }
+
   // Is this a dictionary?
-  if (obj.constructor === Object) {
+  if (typeof obj === 'object') {
     const newObj: any = {};
     for (const key of Object.keys(obj)) {
       newObj[key] = convertFromJsonObj(cc, obj[key]);
@@ -119,6 +120,7 @@ export function convertToJsonObj(cc: ClassConverter, obj: any): any {
   if (!obj) {
     return obj; // Primitive type
   }
+
   // Is this a Node buffer?
   if (obj instanceof Buffer) {
     return { type: 'Buffer', data: obj.toString('base64') };
@@ -135,22 +137,26 @@ export function convertToJsonObj(cc: ClassConverter, obj: any): any {
   if (cc.isRegisteredClass(obj.constructor)) {
     return cc.toJsonObj(obj);
   }
+
   // Is this an array?
   if (Array.isArray(obj)) {
     return obj.map((x: any) => convertToJsonObj(cc, x));
   }
-  // Is this a dictionary?
-  if (obj.constructor === Object) {
-    const newObj: any = {};
-    for (const key of Object.keys(obj)) {
-      newObj[key] = convertToJsonObj(cc, obj[key]);
+
+  if (typeof obj === 'object') {
+    // Is this a dictionary?
+    if (isPlainObject(obj)) {
+      const newObj: any = {};
+      for (const key of Object.keys(obj)) {
+        newObj[key] = convertToJsonObj(cc, obj[key]);
+      }
+      return newObj;
+    } else {
+      // Throw if this is a non-primitive class that was not registered
+      throw new Error(`Object ${obj.constructor.name} not registered for serialisation`);
     }
-    return newObj;
-  }
-  // Throw if this is a non-primitive class that was not registered
-  if (typeof obj === 'object' && !isPlainObject(obj)) {
-    throw new Error(`Object ${obj.constructor.name} not registered for serialisation`);
   }
+
   // Leave alone, assume JSON primitive
   return obj;
 }