Print an error message when trying to load SDF files that don't contain a <world>

src/Server.cc

@@ -182,6 +182,14 @@ Server::Server(const ServerConfig &_config)
  return;
  }
 
+ if (this->dataPtr->sdfRoot.WorldCount() == 0)
+ {
+ ignerr << "SDF file doesn't contain a world. " <<
+ "If you wish to spawn a model, use the ResourceSpawner GUI plugin " <<
+ "or the 'world/<world_name>/create' service.\n";
+ return;
+ }
+
  // Add record plugin
  if (_config.UseLogRecord())
  {

src/Server_TEST.cc

@@ -1088,6 +1088,45 @@ TEST_P(ServerFixture, AddResourcePaths)
  }
 }
 
+/////////////////////////////////////////////////
+TEST_P(ServerFixture, SdfWithoutWorld)
+{
+ // Initialize logging
+ std::string logBasePath = common::joinPaths(PROJECT_BINARY_PATH, "tmp");
+ common::setenv(IGN_HOMEDIR, logBasePath);
+ std::string path = common::uuid();
+ ignLogInit(path, "test.log");
+
+ // Start server with model SDF file
+ ServerConfig serverConfig;
+ serverConfig.SetSdfFile(common::joinPaths(PROJECT_SOURCE_PATH,
+ "test", "worlds", "models", "sphere", "model.sdf"));
+
+ gz::sim::Server server(serverConfig);
+ EXPECT_FALSE(server.Running());
+ EXPECT_FALSE(*server.Running(0));
+
+ // Check error message in log file
+ std::string logFullPath = common::joinPaths(logBasePath, path, "test.log");
+ std::ifstream ifs(logFullPath.c_str(), std::ios::in);
+ bool errFound = false;
+ while ((!errFound) && (!ifs.eof()))
+ {
+ std::string line;
+ std::getline(ifs, line);
+ std::string errString = "SDF file doesn't contain a world. ";
+ errString += "If you wish to spawn a model, ";
+ errString += "use the ResourceSpawner GUI plugin ";
+ errString += "or the 'world/<world_name>/create' service.";
+ errFound = (line.find(errString) != std::string::npos);
+ }
+ EXPECT_TRUE(errFound);
+
+ // Stop logging
+ ignLogClose();
+ common::removeAll(logBasePath);
+}
+
 // Run multiple times. We want to make sure that static globals don't cause
 // problems.
 INSTANTIATE_TEST_SUITE_P(ServerRepeat, ServerFixture, ::testing::Range(1, 2));