Refactors mongodb persister a little (#472)

This is so that we can more easily test the persister,
but allowing one to inject a custom client. The old
way prevented that. This now then makes the behavior
inline with the other persisters.

burr/integrations/persisters/b_mongodb.py

@@ -10,14 +10,16 @@
 logger = logging.getLogger(__name__)
 
 
-class MongoDBPersister(persistence.BaseStatePersister):
+class MongoDBBasePersister(persistence.BaseStatePersister):
     """A class used to represent a MongoDB Persister.
 
     Example usage:
 
     .. code-block:: python
 
-       persister = MongoDBPersister(uri='mongodb://user:pass@localhost:27017', db_name='mydatabase', collection_name='mystates')
+       persister = MongoDBBasePersister.from_values(uri='mongodb://user:pass@localhost:27017',
+                                                    db_name='mydatabase',
+                                                    collection_name='mystates')
        persister.save(
            partition_key='example_partition',
            app_id='example_app',
@@ -28,20 +30,46 @@ class MongoDBPersister(persistence.BaseStatePersister):
        )
        loaded_state = persister.load(partition_key='example_partition', app_id='example_app', sequence_id=1)
        print(loaded_state)
+
+    Note: this is called MongoDBBasePersister because we had to change the constructor and wanted to make
+     this change backwards compatible.
     """
 
-    def __init__(
-        self,
+    @classmethod
+    def from_values(
+        cls,
         uri="mongodb://localhost:27017",
         db_name="mydatabase",
         collection_name="mystates",
         serde_kwargs: dict = None,
         mongo_client_kwargs: dict = None,
-    ):
-        """Initializes the MongoDBPersister class."""
+    ) -> "MongoDBBasePersister":
+        """Initializes the MongoDBBasePersister class."""
         if mongo_client_kwargs is None:
             mongo_client_kwargs = {}
-        self.client = MongoClient(uri, **mongo_client_kwargs)
+        client = MongoClient(uri, **mongo_client_kwargs)
+        return cls(
+            client=client,
+            db_name=db_name,
+            collection_name=collection_name,
+            serde_kwargs=serde_kwargs,
+        )
+
+    def __init__(
+        self,
+        client,
+        db_name="mydatabase",
+        collection_name="mystates",
+        serde_kwargs: dict = None,
+    ):
+        """Initializes the MongoDBBasePersister class.
+
+        :param client: the mongodb client to use
+        :param db_name: the name of the database to use
+        :param collection_name: the name of the collection to use
+        :param serde_kwargs: serializer/deserializer keyword arguments to pass to the state object
+        """
+        self.client = client
         self.db = self.client[db_name]
         self.collection = self.db[collection_name]
         self.serde_kwargs = serde_kwargs or {}
@@ -101,3 +129,29 @@ def save(
 
     def __del__(self):
         self.client.close()
+
+
+class MongoDBPersister(MongoDBBasePersister):
+    """A class used to represent a MongoDB Persister.
+
+    This class is deprecated. Please use MongoDBBasePersister instead.
+    """
+
+    def __init__(
+        self,
+        uri="mongodb://localhost:27017",
+        db_name="mydatabase",
+        collection_name="mystates",
+        serde_kwargs: dict = None,
+        mongo_client_kwargs: dict = None,
+    ):
+        """Initializes the MongoDBPersister class."""
+        if mongo_client_kwargs is None:
+            mongo_client_kwargs = {}
+        client = MongoClient(uri, **mongo_client_kwargs)
+        super(MongoDBPersister, self).__init__(
+            client=client,
+            db_name=db_name,
+            collection_name=collection_name,
+            serde_kwargs=serde_kwargs,
+        )

docs/reference/persister.rst

@@ -53,7 +53,7 @@ Currently we support the following, although we highly recommend you contribute
 
    .. automethod:: __init__
 
-.. autoclass:: burr.integrations.persisters.b_mongodb.MongoDBPersister
+.. autoclass:: burr.integrations.persisters.b_mongodb.MongoDBBasePersister
    :members:
 
    .. automethod:: __init__

tests/integrations/persisters/test_b_mongodb.py

@@ -3,15 +3,15 @@
 import pytest
 
 from burr.core import state
-from burr.integrations.persisters.b_mongodb import MongoDBPersister
+from burr.integrations.persisters.b_mongodb import MongoDBBasePersister, MongoDBPersister
 
 if not os.environ.get("BURR_CI_INTEGRATION_TESTS") == "true":
     pytest.skip("Skipping integration tests", allow_module_level=True)
 
 
 @pytest.fixture
 def mongodb_persister():
-    persister = MongoDBPersister(
+    persister = MongoDBBasePersister.from_values(
         uri="mongodb://localhost:27017", db_name="testdb", collection_name="testcollection"
     )
     yield persister
@@ -35,3 +35,14 @@ def test_list_app_ids(mongodb_persister):
 def test_load_nonexistent_key(mongodb_persister):
     state_data = mongodb_persister.load("pk", "nonexistent_key")
     assert state_data is None
+
+
+def test_backwards_compatible_persister():
+    persister = MongoDBPersister(
+        uri="mongodb://localhost:27017", db_name="testdb", collection_name="backwardscompatible"
+    )
+    persister.save("pk", "app_id", 5, "pos", state.State({"a": 5, "b": 5}), "completed")
+    data = persister.load("pk", "app_id", 5)
+    assert data["state"].get_all() == {"a": 5, "b": 5}
+
+    persister.collection.drop()