make pickling backwards-compatible

Author: BenjaminLowry

conjure_python_client/_http/requests_client.py

@@ -219,8 +219,9 @@ def create(
 
 class TransportAdapter(HTTPAdapter):
     """Transport adapter that allows customising ssl things"""
+    ENABLE_KEEP_ALIVE_ATTR = "_enable_keep_alive"
 
-    __attrs__ = HTTPAdapter.__attrs__ + ["_enable_keep_alive"]
+    __attrs__ = HTTPAdapter.__attrs__ + [ENABLE_KEEP_ALIVE_ATTR]
 
     def __init__(self, *args, enable_keep_alive: bool = False, **kwargs):
         self._enable_keep_alive = enable_keep_alive
@@ -247,6 +248,11 @@ def init_poolmanager(
             **pool_kwargs
         )
 
+    def __setstate__(self, state):
+        if self.ENABLE_KEEP_ALIVE_ATTR not in state:
+            state[self.ENABLE_KEEP_ALIVE_ATTR] = False
+        super().__setstate__(state)
+
 
 class ConjureHTTPError(HTTPError):
     """An HTTPError from a Conjure Service with ``SerializableError``

test/http/__init__.py test/_http/__init__.pytest/http/__init__.py renamed to test/_http/__init__.py

@@ -1,3 +1,4 @@
+import pickle
 import sys
 
 from conjure_python_client._http.requests_client import (
@@ -12,9 +13,7 @@
 
 def test_can_enable_keep_alives_in_transport_adapter():
     assert (
-        TransportAdapter(
-            max_retries=12, enable_keep_alive=True
-        )._enable_keep_alive
+        TransportAdapter(max_retries=12, enable_keep_alive=True)._enable_keep_alive
         is True
     )
     assert TransportAdapter(max_retries=12)._enable_keep_alive is False
@@ -38,3 +37,24 @@ def test_keep_alive_passed_in_state_in_transport_adapter():
     )
     assert ta._enable_keep_alive is True
     assert ta.max_retries.total == 12
+
+
+def test_transport_adapter_pickles_correctly():
+    pre_adapter = TransportAdapter(enable_keep_alive=True)
+    post_adapter = pickle.loads(pickle.dumps(pre_adapter))
+    assert post_adapter._enable_keep_alive is True
+    assert post_adapter._pool_connections == pre_adapter._pool_connections
+    assert post_adapter._pool_maxsize == pre_adapter._pool_maxsize
+
+
+def test_transport_adapter_can_be_unpickled_from_old_pickle():
+    # Remove "_enable_keep_alive" attr from get state so that when picked it emulates an old instance of this
+    # class being pickled before this attr was added. Then verify we can pickle and unpickle to validate we
+    # give it a default value if not present when unpickled.
+    TransportAdapter.__getstate__ = lambda self: {
+        attr: getattr(self, attr, None)
+        for attr in self.__attrs__
+        if attr != TransportAdapter.ENABLE_KEEP_ALIVE_ATTR
+    }
+    adapter = pickle.loads(pickle.dumps(TransportAdapter()))
+    assert adapter._enable_keep_alive is False