Make it possible to guess Thingy.client from Thingy.database

As of now:
- Thingy.client can be guessed from Thingy.database
- Thingy.database can be guessed from Thingy._client or Thingy._collection
- Thingy.collection can be guessed from Thingy.database

mongo_thingy/__init__.py

@@ -36,15 +36,19 @@ def collection_name(cls):
 
     @classproperty
     def client(cls):
-        return cls._client
+        return cls.get_client()
+
+    @classmethod
+    def _get_client(cls, database):
+        return database.client
 
     @classmethod
     def _get_database(cls, collection, name):
         if collection:
             return collection.database
-        if cls.client and name:
-            return cls.client[name]
-        raise AttributeError("Undefined client.")
+        if cls._client and name:
+            return cls._client[name]
+        raise AttributeError("Undefined database.")
 
     @classmethod
     def _get_table(cls, database, table_name):
@@ -58,6 +62,12 @@ def _get_database_name(cls, database):
     def _get_table_name(cls, table):
         return table.name
 
+    @classmethod
+    def get_client(cls):
+        if cls._client:
+            return cls._client
+        return cls._get_client(cls.database)
+
     @classmethod
     def get_collection(cls):
         return cls.get_table()

tests/__init__.py

@@ -10,6 +10,10 @@ def test_thingy_database(TestThingy, database):
     assert TestThingy.database == database
 
 
+def test_thingy_client(TestThingy, client):
+    assert TestThingy.client == client
+
+
 def test_thingy_collection(TestThingy, collection):
     assert TestThingy.collection == collection
 
@@ -54,13 +58,27 @@ class FooBar(Thingy):
     assert FooBar.collection_name == collection.name
 
 
+def test_thingy_database_from_client(client):
+    class FooBar(Thingy):
+        _client = client
+
+    assert FooBar.database == client.foo
+
+
 def test_thingy_database_from_collection(collection):
     class Foo(Thingy):
         _collection = collection
 
     assert Foo.database == collection.database
 
 
+def test_thingy_client_from_database(database):
+    class Foo(Thingy):
+        _database = database
+
+    assert Foo.client == database.client
+
+
 def test_thingy_collection_from_database(database):
     class Foo(Thingy):
         _database = database
@@ -106,22 +124,26 @@ def test_thingy_count(TestThingy, collection):
 @pytest.mark.parametrize("connect", [connect, Thingy.connect])
 @pytest.mark.parametrize("disconnect", [disconnect, Thingy.disconnect])
 def test_thingy_connect_disconnect(connect, disconnect):
-    assert Thingy.client is None
+    with pytest.raises(AttributeError):
+        Thingy.client
 
     connect()
     assert isinstance(Thingy.client, MongoClient)
     assert Thingy._database is None
 
     disconnect()
-    assert Thingy.client is None
+    assert Thingy._client is None
 
     connect("mongodb://hostname/database")
     assert isinstance(Thingy.client, MongoClient)
     assert Thingy.database
     assert Thingy.database.name == "database"
     disconnect()
 
-    assert Thingy.client is None
+    assert Thingy._client is None
+    with pytest.raises(AttributeError):
+        Thingy.client
+
     assert Thingy._database is None
     with pytest.raises(AttributeError):
         Thingy.database