added support for multiple DB connections

Author: dmalan

src/cs50/sql.py

@@ -275,19 +275,24 @@ def execute(self, sql, *args, **kwargs):
             # Infer whether app is defined
             assert flask.current_app
 
-            # If new context
+            # If no connections to any databases yet
+            if not hasattr(flask.g, "_connections"):
+                setattr(flask.g, "_connections", {})
+            connections = getattr(flask.g, "_connections")
+
+            # If not yet connected to this database
             # https://flask.palletsprojects.com/en/1.1.x/appcontext/#storing-data
-            if "_connection" not in flask.g:
+            if id(self) not in connections:
 
                 # Connect to database
-                flask.g._connection = self._engine.connect()
+                connections[id(self)] = self._engine.connect()
 
                 # Disconnect from database later
                 if _teardown_appcontext not in flask.current_app.teardown_appcontext_funcs:
                     flask.current_app.teardown_appcontext(_teardown_appcontext)
 
-            # Use context's connection
-            connection = flask.g._connection
+            # Use this connection
+            connection = connections[id(self)]
 
         except (ModuleNotFoundError, AssertionError):
 
@@ -533,6 +538,5 @@ def _parse_placeholder(token):
 def _teardown_appcontext(exception=None):
     """Closes context's database connection, if any."""
     import flask
-    connection = flask.g.pop("_connection", None)
-    if connection:
+    for connection in flask.g.pop("_connections", {}).values():
         connection.close()