fix: preserve user supplied session in S3FileSystem constructor

Author: Philipp Falke

s3fs/core.py

@@ -214,7 +214,7 @@ def __init__(
         self.use_ssl = use_ssl
         self.cache_regions = cache_regions
         self._s3 = None
-        self.session = None
+        self.session = session
 
     @property
     def s3(self):
@@ -375,7 +375,8 @@ async def set_session(self, refresh=False, kwargs={}):
             config_kwargs["signature_version"] = UNSIGNED
 
         conf = AioConfig(**config_kwargs)
-        self.session = aiobotocore.AioSession(**self.kwargs)
+        if self.session is None:
+            self.session = aiobotocore.AioSession(**self.kwargs)
 
         for parameters in (config_kwargs, self.kwargs, init_kwargs, client_kwargs):
             for option in ("region_name", "endpoint_url"):

s3fs/tests/test_s3fs.py

@@ -227,6 +227,14 @@ def test_config_kwargs_class_attributes_override():
     assert s3.connect().meta.config.read_timeout == 120
 
 
+def test_user_session_is_preserved():
+    from aiobotocore.session import get_session
+    session = get_session()
+    s3 = S3FileSystem(session=session)
+    s3.connect()
+    assert s3.session == session
+
+
 def test_idempotent_connect(s3):
     first = s3.s3
     assert s3.connect(refresh=True) is not first