SNOW-743102: fix create_engine("snowflake://").dialect (#387)

src/snowflake/sqlalchemy/snowdialect.py

@@ -210,7 +210,11 @@ def create_connect_args(self, url):
                 raise sa_exc.ArgumentError(
                     f"Invalid name space is specified: {opts['database']}"
                 )
-        if ".snowflakecomputing.com" not in opts["host"] and not opts.get("port"):
+        if (
+            "host" in opts
+            and ".snowflakecomputing.com" not in opts["host"]
+            and not opts.get("port")
+        ):
             opts["account"] = opts["host"]
             if "." in opts["account"]:
                 # remove region subdomain

tests/test_core.py

@@ -173,6 +173,17 @@ def test_connect_args():
         engine.dispose()
 
 
+def test_create_dialect():
+    """
+    Tests getting only dialect object through create_engine
+    """
+    engine = create_engine("snowflake://")
+    try:
+        assert engine.dialect
+    finally:
+        engine.dispose()
+
+
 def test_simple_sql(engine_testaccount):
     """
     Simple SQL by SQLAlchemy