check db_url just before actual operation is executed (#13)

sqlcsv/cli.py

@@ -50,7 +50,7 @@ def _flag_to_bool(spec):
 
 
 @click.group()
-@click.option('-u', '--db-url', envvar='SQLCSV_DB_URL', required=True,
+@click.option('-u', '--db-url', envvar='SQLCSV_DB_URL',
               help='Datasbase connection URL.')
 @click.option('-p', '--pre-sql', default=None,
               help='SQL to be run before main operation.')

sqlcsv/command.py

@@ -30,6 +30,9 @@ def __init__(self, db_url, pre_sql, post_sql, transaction, header, dialect):
 
     @contextmanager
     def _connect_exec(self):
+        if not self._db_url:
+            raise ValueError('Database connection URL is not set')
+
         engine = create_engine(self._db_url)
 
         with engine.begin() if self._transaction else engine.connect() as conn:

tests/test_command.py

@@ -1,7 +1,7 @@
 from io import StringIO
 from unittest.mock import patch
 
-from pytest import fixture
+from pytest import fixture, raises
 from sqlalchemy import create_engine
 
 import sqlcsv.command
@@ -63,6 +63,14 @@ def test_connect_exec(db, command_args):
         assert result == []
 
 
+def test_connect_exec_without_db_url(db, command_args):
+    command_args['db_url'] = None
+    cmd = sqlcsv.command.Command(**command_args)
+    with raises(ValueError):
+        with cmd._connect_exec():
+            pass
+
+
 def test_connect_exec_with_transaction(db, command_args):
     command_args['transaction'] = True
     cmd = sqlcsv.command.Command(**command_args)