Check for JSON-RPC errors, and add better logging for it

src/rpc/client.cpp

@@ -37,6 +37,7 @@
 #include "misc_log_ex.h"     // monero/contrib/epee/include
 #include "net/http_client.h" // monero/contrib/epee/include
 #include "net/zmq.h"         // monero/src
+#include "serialization/json_object.h" // monero/src
 
 namespace lws
 {
@@ -160,6 +161,32 @@ namespace rpc
     };
   } // detail
 
+  expect<void> client::get_response(cryptonote::rpc::Message& response, const std::chrono::seconds timeout, const source_location loc)
+  {
+    expect<std::string> message = get_message(timeout);
+    if (!message)
+      return message.error();
+
+    try
+    {
+      cryptonote::rpc::FullMessage fm{std::move(*message)};
+      const cryptonote::rpc::error json_error = fm.getError();
+      if (!json_error.use)
+      {
+        response.fromJson(fm.getMessage());
+        return success();
+      }
+
+      MERROR("Server returned RPC error: " << json_error.message << " with code " << json_error.code << " called from " << loc);
+    }
+    catch (const cryptonote::json::JSON_ERROR& error)
+    {
+      MERROR("Failed to parse json response: " << error.what() << " called from " << loc);
+    }
+
+    return {lws::error::bad_daemon_response};
+  }
+
   expect<std::string> client::get_message(std::chrono::seconds timeout)
   {
     MONERO_PRECOND(ctx != nullptr);

src/rpc/client.h

@@ -38,6 +38,7 @@
 #include "rpc/message.h"   // monero/src
 #include "rpc/daemon_pub.h"
 #include "rpc/rates.h"
+#include "util/source_location.h"
 
 namespace lws
 {
@@ -70,6 +71,9 @@ namespace rpc
       : ctx(std::move(ctx)), daemon(), daemon_sub(), signal_sub()
     {}
 
+    //! Expect `response` as the next message payload unless error.
+    expect<void> get_response(cryptonote::rpc::Message& response, std::chrono::seconds timeout, source_location loc);
+
   public:
     //! A client with no connection (all send/receive functions fail).
     explicit client() noexcept
@@ -125,18 +129,13 @@ namespace rpc
     //! \return Next available RPC message response from server
     expect<std::string> get_message(std::chrono::seconds timeout);
 
-    //! \return RPC response `M`, waiting a max of `timeout` seconds.
+    //! \return RPC response `M`, waiting a max of `timeout` seconds. Log errors as from `loc`.
     template<typename M>
-    expect<M> receive(std::chrono::seconds timeout)
+    expect<M> receive(const std::chrono::seconds timeout, const source_location loc = {})
     {
-      expect<std::string> message = get_message(timeout);
-      if (!message)
-        return message.error();
-
-      cryptonote::rpc::FullMessage fm{std::move(*message)};
-      M out{};
-      out.fromJson(fm.getMessage());
-      return out;
+      M response{};
+      MONERO_CHECK(get_response(response, timeout, loc));
+      return response;
     }
 
     /*!