give a nicer error if URI has no dbname

Author: dcrosta

flask_pymongo/__init__.py

@@ -149,6 +149,10 @@ def init_app(self, app, uri=None, *args, **kwargs):
         parsed_uri = uri_parser.parse_uri(uri)
         database_name = parsed_uri["database"]
 
+        # Avoid a more confusing error later when we try to get the DB
+        if not database_name:
+            raise ValueError("Your URI must specify a database name")
+
         # Try to delay connecting, in case the app is loaded before forking, per
         # http://api.mongodb.com/python/current/faq.html#is-pymongo-fork-safe
         kwargs.setdefault("connect", False)

flask_pymongo/tests/test_config.py

@@ -81,6 +81,12 @@ def test_it_doesnt_connect_by_default(self):
         with pytest.raises(CouldNotConnect):
             _wait_until_connected(mongo, timeout=0.2)
 
+    def test_it_requires_db_name_in_uri(self):
+        uri = "mongodb://localhost:{}".format(self.port)
+
+        with pytest.raises(ValueError):
+            flask_pymongo.PyMongo(self.app, uri)
+
 
 def _wait_until_connected(mongo, timeout=1.0):
     start = time.time()