only wrap callback in command handler if in a transaction

Author: daprahamian

lib/wireprotocol/command.js

@@ -23,6 +23,7 @@ function command(server, ns, cmd, options, callback) {
  const pool = server.s.pool;
  const readPreference = getReadPreference(cmd, options);
  const shouldUseOpMsg = supportsOpMsg(server);
+ const session = options.session;
 
  let finalCmd = Object.assign({}, cmd);
  if (
@@ -37,7 +38,7 @@ function command(server, ns, cmd, options, callback) {
  };
  }
 
- const err = decorateWithSessionsData(finalCmd, options.session, options);
+ const err = decorateWithSessionsData(finalCmd, session, options);
  if (err) {
  return callback(err);
  }
@@ -60,19 +61,16 @@ function command(server, ns, cmd, options, callback) {
  ? new Msg(bson, cmdNs, finalCmd, commandOptions)
  : new Query(bson, cmdNs, finalCmd, commandOptions);
 
- const commandResponseHandler = function(err) {
- if (
- options.session &&
- options.session.transaction &&
- err &&
- err instanceof MongoError &&
- err.hasErrorLabel('TransientTransactionError')
- ) {
- options.session.transaction.unpinServer();
- }
+ const inTransaction = session && (session.inTransaction() || isTransactionCommand(finalCmd));
+ const commandResponseHandler = inTransaction
+ ? function(err) {
+ if (err && err instanceof MongoError && err.hasErrorLabel('TransientTransactionError')) {
+ session.transaction.unpinServer();
+ }
 
- return callback.apply(null, arguments);
- };
+ return callback.apply(null, arguments);
+ }
+ : callback;
 
  try {
  pool.write(message, commandOptions, commandResponseHandler);