Empty files with trailing slash are sometimes treated as directories and sometimes treated as regular files

import boto3
from s3fs import S3FileSystem
from pprint  import pprint
TEST_AWS_S3_PORT = 5555
TEST_AWS_ENDPOINT_URL = f'http://127.0.0.1:{TEST_AWS_S3_PORT}/'

boto_client = boto3.client('s3', endpoint_url=TEST_AWS_ENDPOINT_URL)
fs = S3FileSystem(client_kwargs={'endpoint_url': TEST_AWS_ENDPOINT_URL})

boto_client.create_bucket(Bucket='test-bucket')
boto_client.put_object(
    Bucket='test-bucket', Key='empty-dir/', Body='',
)

pprint(fs.ls('test-bucket', detail=True))
pprint(fs.info('test-bucket/empty-dir/'))
print(fs.isdir('test-bucket/empty-dir/'))
print(fs.ls('test-bucket/empty-dir/'))

The code above first creates an empty file using that ends with a trailing slash. Then it tries to run s3fs's ls on the parent directory, which identifies that file as a directory;

[{'Key': 'test-bucket/empty-dir',
  'Size': 0,
  'StorageClass': 'DIRECTORY',
  'name': 'test-bucket/empty-dir',
  'size': 0,
  'type': 'directory'}]

Also the second and the third calls (info() and isdir()) claims it is a directory;

{'Key': 'test-bucket/empty-dir',
 'Size': 0,
 'StorageClass': 'DIRECTORY',
 'name': 'test-bucket/empty-dir',
 'size': 0,
 'type': 'directory'}
True

though when we try to do ls/walk etc it behaves like a file. The following is the result of .ls('bucket/empty-dir/');

['test-bucket/empty-dir/']

instead I would have expected it to return an empty list

Start by running the provided boto3 and S3FileSystem reproduction against the configured S3 endpoint, then trace the implementations behind ls(), info(), and isdir() for a zero-byte key ending in '/'. Done means the key is classified consistently across parent listing, info, isdir, and ls, with ls('test-bucket/empty-dir/') returning the expected empty list.