fix RPC server to handle exceptions in requests and return them as son values

lib/browser/rpc.js

@@ -212,6 +212,23 @@ function makeRequest(url, data) {
     return JSON.parse(responseText);
 }
 
+//returns an object from rpc serialized json value
+function deserialize_json_value(value) {
+    let result = {};
+    for (let index = 0; index < value.keys.length; index++) {
+        var propName = value.keys[index];
+        var propValue = value.values[index];
+        if (propValue.type && propValue.type == 'dict') {
+            result[propName] = deserialize_json_value(propValue);
+        }
+        else {
+            result[propName] = propValue.value;
+        }
+    }
+   
+    return result;
+}
+
 function sendRequest(command, data, host = sessionHost) {
     if (!host) {
         throw new Error('Must first create RPC session with a valid host');
@@ -226,9 +243,13 @@ function sendRequest(command, data, host = sessionHost) {
         let error = response && response.error;
 
         // Remove the type prefix from the error message (e.g. "Error: ").
-        if (error) {
+        if (error && error.replace) {
             error = error.replace(/^[a-z]+: /i, '');
         }
+        else if (error.type && error.type == 'dict') {
+            let responseError = deserialize_json_value(error);
+            throw responseError;
+        }
 
         throw new Error(error || `Invalid response for "${command}"`);
     }

src/rpc.cpp

@@ -360,8 +360,25 @@ json RPCServer::perform_request(std::string name, const json &args) {
         assert(action);
 
         m_worker.add_task([=] {
+            try {
                 return action(args);
+            }
+            catch (jsc::Exception ex) {
+                json exceptionAsJson = nullptr;
+                try {
+                    exceptionAsJson = serialize_json_value(ex);
+                }
+                catch (...) {
+                    exceptionAsJson = {{"error", "An exception occured while processing the request. Could not serialize the exception as JSON"}};
+                }
+                
+                 return (json){{"error", exceptionAsJson}};
+            }
+            catch (std::exception &exception) {
+                return (json){{"error", exception.what()}};
+            }
         });
+
     }
 
     try {