Merge pull request #493 from mattbennett/config-command

add a command to output parsed config after env var substitution

nameko/cli/commands.py

@@ -46,6 +46,31 @@ def main(args):
         main(args)
 
 
+class ShowConfig(Command):
+    """ Output as YAML string the configuration that would be passed to a
+    service.
+
+    Useful for viewing config files that load values from environement
+    variables.
+    """
+
+    name = 'show-config'
+
+    @staticmethod
+    def init_parser(parser):
+
+        parser.add_argument(
+            '--config', default='config.yaml',
+            help='The YAML configuration file')
+
+        return parser
+
+    @staticmethod
+    def main(args):
+        from .show_config import main
+        main(args)
+
+
 class Run(Command):
     """Run nameko services.  Given a python path to a module containing one or
     more nameko services, will host and run them. By default this will try to

nameko/cli/show_config.py

@@ -0,0 +1,11 @@
+from __future__ import print_function
+
+import yaml
+
+
+def main(args):
+
+    with open(args.config) as fle:
+        config = yaml.load(fle)
+
+    print(yaml.dump(config, default_flow_style=False))

test/cli/test_show_config.py

@@ -0,0 +1,41 @@
+from textwrap import dedent
+
+from mock import patch
+
+from nameko.cli.commands import ShowConfig
+from nameko.cli.main import setup_parser, setup_yaml_parser
+
+
+@patch('nameko.cli.main.os')
+def test_main(mock_os, tmpdir, capsys):
+
+    config = tmpdir.join('config.yaml')
+    config.write("""
+        FOO: ${FOO:foobar}
+        BAR: ${BAR}
+    """)
+
+    parser = setup_parser()
+    setup_yaml_parser()
+    args = parser.parse_args([
+        'show-config',
+        '--config',
+        config.strpath,
+    ])
+
+    mock_os.environ = {
+        'BAR': '[1,2,3]'
+    }
+
+    ShowConfig.main(args)
+    out, _ = capsys.readouterr()
+
+    expected = dedent("""
+        BAR:
+        - 1
+        - 2
+        - 3
+        FOO: foobar
+    """).strip()
+
+    assert out.strip() == expected