Method EnsureIsDirAsync

cpp/src/arrow/filesystem/s3fs.cc:2859–2886

Check to make sure the given path is not a file Returns true if the path seems to be a directory, false if it is a file

  //
  // Returns true if the path seems to be a directory, false if it is a file
  Future<bool> EnsureIsDirAsync(const std::string& bucket, const std::string& key) {
    if (key.empty()) {
      // There is no way for a bucket to be a file
      return Future<bool>::MakeFinished(true);
    }
    auto self = shared_from_this();
    return DeferNotOk(
        SubmitIO(io_context_, [self, bucket, key]() mutable -> Result<bool> {
          S3Model::HeadObjectRequest req;
          req.SetBucket(ToAwsString(bucket));
          req.SetKey(ToAwsString(key));

          ARROW_ASSIGN_OR_RAISE(auto client_lock, self->holder_->Lock());
          auto outcome = client_lock.Move()->HeadObject(req);
          if (outcome.IsSuccess()) {
            return IsDirectory(key, outcome.GetResult());
          }
          if (IsNotFound(outcome.GetError())) {
            // If we can't find it then it isn't a file.
            return true;
          } else {
            return ErrorToStatus(
                std::forward_as_tuple("When getting information for key '", key,
                                      "' in bucket '", bucket, "': "),
                "HeadObject", outcome.GetError());
          }
        }));
  }

  // Some operations require running multiple S3 calls, either in parallel or serially. We
  // need to ensure that the S3 filesystem instance stays valid and that S3 isn't