Extract error information from JSON.

When OSRM returns an error, it (often?) includes an error code/message
in the returned JSON object. This change extracts this code/message and
returns it to the caller of libosrmc. This makes it easier to debug
failures, but also makes it possible to react to errors such as
`NoRoute`.

The errors are extracted as both `code`/`message`, and a new
`osrmc_error_code` is introduced to allow the caller to extract the
code.

bindings/osrm_c89.c

@@ -84,7 +84,7 @@ int main(int argc, char** argv) {
 
   /* If we got here on a failure path notify the user */
   if (error) {
-    fprintf(stderr, "Error: %s\n", osrmc_error_message(error));
+    fprintf(stderr, "Error: code=%s, message=%s\n", osrmc_error_code(error), osrmc_error_message(error));
     osrmc_error_destruct(error);
     return EXIT_FAILURE;
   }

libosrmc/osrmc.cc

@@ -26,9 +26,28 @@ int osrmc_is_abi_compatible(void) { return osrmc_get_version() >> 16u == OSRMC_V
 /* API */
 
 struct osrmc_error final {
+  std::string code;
   std::string message;
 };
 
+static void osrmc_error_from_exception(const std::exception& e, osrmc_error_t* error) {
+  *error = new osrmc_error{"Exception", e.what()};
+}
+
+static void osrmc_error_from_json(osrm::json::Object& json, osrmc_error_t* error) try {
+  auto code = json.values["code"].get<osrm::json::String>().value;
+  auto message = json.values["message"].get<osrm::json::String>().value;
+  if (code.empty()) {
+    code = "Unknown";
+  }
+
+  *error = new osrmc_error{code, message};
+} catch (const std::exception& e) {
+  osrmc_error_from_exception(e, error);
+}
+
+const char* osrmc_error_code(osrmc_error_t error) { return error->code.c_str(); }
+
 const char* osrmc_error_message(osrmc_error_t error) { return error->message.c_str(); }
 
 void osrmc_error_destruct(osrmc_error_t error) { delete error; }
@@ -48,7 +67,7 @@ osrmc_config_t osrmc_config_construct(const char* base_path, osrmc_error_t* erro
 
   return reinterpret_cast<osrmc_config_t>(out);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -60,7 +79,7 @@ osrmc_osrm_t osrmc_osrm_construct(osrmc_config_t config, osrmc_error_t* error) t
 
   return reinterpret_cast<osrmc_osrm_t>(out);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -74,7 +93,7 @@ void osrmc_params_add_coordinate(osrmc_params_t params, float longitude, float l
 
   params_typed->coordinates.emplace_back(std::move(longitude_typed), std::move(latitude_typed));
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
 }
 
 void osrmc_params_add_coordinate_with(osrmc_params_t params, float longitude, float latitude, float radius, int bearing,
@@ -90,15 +109,15 @@ void osrmc_params_add_coordinate_with(osrmc_params_t params, float longitude, fl
   params_typed->radiuses.emplace_back(radius);
   params_typed->bearings.emplace_back(std::move(bearing_typed));
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
 }
 
 osrmc_route_params_t osrmc_route_params_construct(osrmc_error_t* error) try {
   auto* out = new osrm::RouteParameters;
 
   return reinterpret_cast<osrmc_route_params_t>(out);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -126,10 +145,10 @@ osrmc_route_response_t osrmc_route(osrmc_osrm_t osrm, osrmc_route_params_t param
   if (status == osrm::Status::Ok)
     return reinterpret_cast<osrmc_route_response_t>(out);
 
-  *error = new osrmc_error{"service request failed"};
+  osrmc_error_from_json(*out, error);
   return nullptr;
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -142,7 +161,7 @@ void osrmc_route_with(osrmc_osrm_t osrm, osrmc_route_params_t params, osrmc_wayp
   const auto status = osrm_typed->Route(*params_typed, result);
 
   if (status != osrm::Status::Ok) {
-    *error = new osrmc_error{"service request failed"};
+    osrmc_error_from_json(result, error);
     return;
   }
 
@@ -159,7 +178,7 @@ void osrmc_route_with(osrmc_osrm_t osrm, osrmc_route_params_t params, osrmc_wayp
     (void)handler(data, name.c_str(), longitude, latitude);
   }
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
 }
 
 void osrmc_route_response_destruct(osrmc_route_response_t response) {
@@ -175,7 +194,7 @@ float osrmc_route_response_distance(osrmc_route_response_t response, osrmc_error
   const auto distance = route.values["distance"].get<osrm::json::Number>().value;
   return distance;
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return INFINITY;
 }
 
@@ -188,15 +207,15 @@ float osrmc_route_response_duration(osrmc_route_response_t response, osrmc_error
   const auto duration = route.values["duration"].get<osrm::json::Number>().value;
   return duration;
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return INFINITY;
 }
 
 osrmc_table_params_t osrmc_table_params_construct(osrmc_error_t* error) try {
   auto* out = new osrm::TableParameters;
   return reinterpret_cast<osrmc_table_params_t>(out);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -208,14 +227,14 @@ void osrmc_table_params_add_source(osrmc_table_params_t params, size_t index, os
   auto* params_typed = reinterpret_cast<osrm::TableParameters*>(params);
   params_typed->sources.emplace_back(index);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
 }
 
 void osrmc_table_params_add_destination(osrmc_table_params_t params, size_t index, osrmc_error_t* error) try {
   auto* params_typed = reinterpret_cast<osrm::TableParameters*>(params);
   params_typed->destinations.emplace_back(index);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
 }
 
 osrmc_table_response_t osrmc_table(osrmc_osrm_t osrm, osrmc_table_params_t params, osrmc_error_t* error) try {
@@ -228,10 +247,10 @@ osrmc_table_response_t osrmc_table(osrmc_osrm_t osrm, osrmc_table_params_t param
   if (status == osrm::Status::Ok)
     return reinterpret_cast<osrmc_table_response_t>(out);
 
-  *error = new osrmc_error{"service request failed"};
+  osrmc_error_from_json(*out, error);
   return nullptr;
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -249,15 +268,15 @@ float osrmc_table_response_duration(osrmc_table_response_t response, unsigned lo
 
   return duration;
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return INFINITY;
 }
 
 osrmc_nearest_params_t osrmc_nearest_params_construct(osrmc_error_t* error) try {
   auto* out = new osrm::NearestParameters;
   return reinterpret_cast<osrmc_nearest_params_t>(out);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -269,7 +288,7 @@ osrmc_match_params_t osrmc_match_params_construct(osrmc_error_t* error) try {
   auto* out = new osrm::MatchParameters;
   return reinterpret_cast<osrmc_match_params_t>(out);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
   return nullptr;
 }
 
@@ -286,5 +305,5 @@ void osrmc_match_params_add_timestamp(osrmc_match_params_t params, unsigned time
   auto* params_typed = reinterpret_cast<osrm::MatchParameters*>(params);
   params_typed->timestamps.emplace_back(timestamp);
 } catch (const std::exception& e) {
-  *error = new osrmc_error{e.what()};
+  osrmc_error_from_exception(e, error);
 }

libosrmc/osrmc.h

@@ -159,6 +159,7 @@ typedef void (*osrmc_waypoint_handler_t)(void* data, const char* name, float lon
 
 /* Error handling */
 
+OSRMC_API const char* osrmc_error_code(osrmc_error_t error);
 OSRMC_API const char* osrmc_error_message(osrmc_error_t error);
 OSRMC_API void osrmc_error_destruct(osrmc_error_t error);