fix: add cause to transaction errors on transaction commit (#108)

Author: rockwotj

google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreException.java

@@ -28,7 +28,11 @@ public final class FirestoreException extends BaseGrpcServiceException {
  private Status status;
 
  private FirestoreException(String reason, Status status) {
- super(reason, null, status.getCode().value(), false);
+ this(reason, status, null);
+ }
+
+ private FirestoreException(String reason, Status status, @Nullable Throwable cause) {
+ super(reason, cause, status.getCode().value(), false);
 
  this.status = status;
  }
@@ -58,7 +62,18 @@ static FirestoreException invalidState(String message, Object... params) {
  * @return The FirestoreException
  */
  static FirestoreException serverRejected(Status status, String message, Object... params) {
- return new FirestoreException(String.format(message, params), status);
+ return serverRejected(status, null, message, params);
+ }
+
+ /**
+ * Creates a FirestoreException with the provided GRPC Status code and message in a nested
+ * exception.
+ *
+ * @return The FirestoreException
+ */
+ static FirestoreException serverRejected(
+ Status status, @Nullable Throwable cause, String message, Object... params) {
+ return new FirestoreException(String.format(message, params), status, cause);
  }
 
  /**

google-cloud-firestore/src/main/java/com/google/cloud/firestore/FirestoreImpl.java

@@ -360,7 +360,7 @@ public void onSuccess(final T userResult) {
  @Override
  public void onFailure(Throwable throwable) {
  // Retry failed commits.
- maybeRetry();
+ maybeRetry(throwable);
  }
 
  @Override
@@ -393,7 +393,7 @@ public void run() {
  return callbackResult;
  }
 
- private void maybeRetry() {
+ private void maybeRetry(Throwable throwable) {
  if (attemptsRemaining > 0) {
  span.addAnnotation("retrying");
  runTransactionAttempt(
@@ -406,7 +406,9 @@ private void maybeRetry() {
  span.setStatus(TOO_MANY_RETRIES_STATUS);
  rejectTransaction(
  FirestoreException.serverRejected(
- Status.ABORTED, "Transaction was cancelled because of too many retries."));
+ Status.ABORTED,
+ throwable,
+ "Transaction was cancelled because of too many retries."));
  }
  }