simplifying the config loading so that it uses a default config file

crane/config.py

@@ -1,30 +1,31 @@
-from ConfigParser import ConfigParser
+from ConfigParser import ConfigParser, NoSectionError, NoOptionError
+from contextlib import contextmanager
 import logging
 import os
 
+import pkg_resources
+
 
 _logger = logging.getLogger(__name__)
 
 
-DEFAULT_CONFIG_PATH = '/etc/crane.conf'
+# the default location for a user-defined config file
+CONFIG_PATH = '/etc/crane.conf'
+# the environment variable whose value can override the CONFIG_PATH
 CONFIG_ENV_NAME = 'CRANE_CONFIG_PATH'
+# the resource path for the config file containing default values
+DEFAULT_CONFIG_RESOURCE = 'data/default_config.conf'
 
+# general app settings
 SECTION_GENERAL = 'general'
-
 KEY_DEBUG = 'debug'
 KEY_DATA_DIR = 'data_dir'
 KEY_ENDPOINT = 'endpoint'
 
+# google search appliance settings
 SECTION_GSA = 'gsa'
-
 KEY_URL = 'url'
 
-config_defaults = {
-    KEY_DEBUG: 'false',
-    KEY_DATA_DIR: '/var/lib/crane/metadata/',
-    KEY_ENDPOINT: '',
-    KEY_URL: '',
-}
 
 def load(app):
     """
@@ -35,29 +36,71 @@ def load(app):
 
     :raises IOError: iff a non-default config path is specified but does not exist
     """
-    config_path = os.environ.get(CONFIG_ENV_NAME) or DEFAULT_CONFIG_PATH
-    parser = ConfigParser(defaults=config_defaults)
+    # load default values from the included default config file
+    try:
+        with pkg_resources.resource_stream(__package__, DEFAULT_CONFIG_RESOURCE) as default_config:
+            parser = ConfigParser()
+            parser.readfp(default_config)
+        read_config(app, parser)
+    except IOError:
+        _logger.error('could not open default config file')
+        raise
+
+    # load user-specified config values
+    config_path = os.environ.get(CONFIG_ENV_NAME) or CONFIG_PATH
     try:
         with open(config_path) as config_file:
+            parser = ConfigParser()
             parser.readfp(config_file)
+        read_config(app, parser)
         _logger.info('config loaded from %s' % config_path)
     except IOError:
-        if config_path != DEFAULT_CONFIG_PATH:
+        if config_path != CONFIG_PATH:
             _logger.error('config file not found at path %s' % config_path)
             raise
         # if the user did not specify a config path and there is not a file
         # at the default path, just use the default settings.
         _logger.info('no config specified or found, so using defaults')
 
-    # adding the empty section will allow defaults to be used below
-    for section in [SECTION_GENERAL, SECTION_GSA]:
-        if not parser.has_section(section):
-            parser.add_section(section)
 
-    # [general] section
-    app.config['DEBUG'] = parser.getboolean(SECTION_GENERAL, KEY_DEBUG)
-    app.config[KEY_DATA_DIR] = parser.get(SECTION_GENERAL, KEY_DATA_DIR)
-    app.config[KEY_ENDPOINT] = parser.get(SECTION_GENERAL, KEY_ENDPOINT)
+def read_config(app, parser):
+    """
+    Read the configuration from the parser, and apply it to the app
+
+    :param app:     a flask app
+    :type  app:     Flask
+    :param parser:  a ConfigParser that has a file already loaded
+    :type  parser:  ConfigParser
+    """
+    # "general" section settings
+    with supress(NoSectionError):
+        app.config['DEBUG'] = parser.getboolean(SECTION_GENERAL, KEY_DEBUG)
+
+        # parse other "general" section values
+        for key in (KEY_DATA_DIR, KEY_ENDPOINT):
+            with supress(NoOptionError):
+                app.config[key] = parser.get(SECTION_GENERAL, key)
+
+    # "gsa" (Google Search Appliance) section settings
+    with supress(NoSectionError):
+        section = app.config.setdefault(SECTION_GSA, {})
+
+        for key in (KEY_URL,):
+            with supress(NoOptionError):
+                section[key] = parser.get(SECTION_GSA, key)
 
-    # [gsa] section
-    app.config[SECTION_GSA + '_' + KEY_URL] = parser.get(SECTION_GSA, KEY_URL)
+
+@contextmanager
+def supress(*exceptions):
+    """
+    backported from python 3.4, because it's simple and awesome
+
+    https://docs.python.org/3.4/library/contextlib.html#contextlib.suppress
+
+    :param exceptions:  list of Exception or subclasses
+    :type  exceptions:  list
+    """
+    try:
+        yield
+    except exceptions:
+        pass

crane/data/default_config.conf

@@ -0,0 +1,7 @@
+[general]
+debug: false
+data_dir: /var/lib/crane/metadata/
+endpoint:
+
+[gsa]
+url:

crane/search/__init__.py

@@ -17,7 +17,7 @@ def load_config(app):
     """
     global backend
 
-    url = app.config.get(config.SECTION_GSA + '_' + config.KEY_URL)
+    url = app.config.get(config.SECTION_GSA, {}).get(config.KEY_URL)
     if url:
         backend = GSA(url)
         return

python-crane.spec

@@ -21,6 +21,7 @@ BuildRequires: python-mock
 BuildRequires: python-unittest2
 
 Requires: python-flask >= 0.9
+Requires: python-setuptools
 Requires(post): policycoreutils-python
 Requires(postun): policycoreutils-python
 

requirements.txt

@@ -1,4 +1,6 @@
 Flask>=0.9
 M2Crypto>=0.21.0
 python-dateutil>=1.5
-iniparse>=0.4
+# for pkg_resources
+setuptools
+iniparse>=0.4

setup.py

@@ -23,4 +23,7 @@
     install_requires=requirements,
     tests_require=test_requirements,
     test_suite='unittest2.collector',
+    package_data={
+        'crane': ['data/*.conf'],
+    },
 )

tests/search/test_init.py

@@ -24,7 +24,7 @@ def test_gsa(self):
         mock_app = mock.MagicMock()
         fake_url = 'http://pulpproject.org/search'
         mock_app.config = {
-            config.SECTION_GSA + '_' + config.KEY_URL: fake_url,
+            config.SECTION_GSA: {config.KEY_URL: fake_url},
         }
 
         search.load_config(mock_app)

tests/test_config.py

@@ -11,21 +11,23 @@ def setUp(self):
         self.app = mock.MagicMock()
         self.app.config = {}
 
-    @mock.patch('ConfigParser.ConfigParser.readfp', side_effect=IOError, spec_set=True)
-    @mock.patch('os.environ.get', return_value=None, spec_set=True)
-    def test_defaults(self, mock_get, mock_readfp):
+    @mock.patch('os.environ.get', return_value='/dev/null', spec_set=True)
+    def test_defaults(self, mock_get):
         """
-        test that when no config file is found, and no path was specified,
-        default values get used.
+        test that when no config options are specified, default values get used.
         """
         config.load(self.app)
 
         self.assertTrue(self.app.config.get('DEBUG') is False)
         self.assertEqual(self.app.config.get(config.KEY_DATA_DIR), '/var/lib/crane/metadata/')
         self.assertEqual(self.app.config.get(config.KEY_ENDPOINT), '')
-        configured_gsa_url = self.app.config.get(config.SECTION_GSA + '_' + config.KEY_URL)
+        configured_gsa_url = self.app.config.get(config.SECTION_GSA, {}).get(config.KEY_URL)
         self.assertEqual(configured_gsa_url, '')
 
+    @mock.patch('pkg_resources.resource_stream', side_effect=IOError, spec_set=True)
+    def test_defaults_not_found(self, mock_resource_stream):
+        self.assertRaises(IOError, config.load, self.app)
+
     @mock.patch('os.environ.get', return_value='/a/b/c/idontexist', spec_set=True)
     def test_file_not_found(self, mock_get):
         """
@@ -40,5 +42,19 @@ def test_demo_config(self, mock_get):
 
         self.assertTrue(self.app.config.get('DEBUG') is True)
 
-        configured_gsa_url = self.app.config.get(config.SECTION_GSA + '_' + config.KEY_URL)
+        configured_gsa_url = self.app.config.get(config.SECTION_GSA, {}).get(config.KEY_URL)
         self.assertEqual(configured_gsa_url, 'http://pulpproject.org/search')
+
+
+class TestSupress(unittest.TestCase):
+    def test_supression(self):
+        with config.supress(ValueError):
+            raise ValueError
+
+    def test_does_not_over_supress(self):
+        with config.supress(TypeError):
+            self.assertRaises(ValueError, int, 'notanint')
+
+    def test_supress_multiple(self):
+        with config.supress(TypeError, ValueError):
+            raise ValueError

tests/test_data.py

@@ -52,7 +52,6 @@ def tearDown(self):
     def test_with_metadata_good(self, mock_glob):
         mock_glob.return_value = [demo_data.foo_metadata_path]
         mock_app = mock.MagicMock()
-        mock_app.config = config.config_defaults.copy()
 
         data.load_all(mock_app)
 
@@ -72,7 +71,6 @@ def test_with_metadata_good(self, mock_glob):
     def test_with_metadata_bad(self, mock_error, mock_glob):
         mock_glob.return_value = [demo_data.wrong_version_path]
         mock_app = mock.MagicMock()
-        mock_app.config = config.config_defaults.copy()
 
         data.load_all(mock_app)
 
@@ -87,7 +85,6 @@ def test_with_metadata_bad(self, mock_error, mock_glob):
     def test_with_wrong_path(self, mock_error, mock_glob):
         mock_glob.return_value = ['/a/b/c/d.json']
         mock_app = mock.MagicMock()
-        mock_app.config = config.config_defaults.copy()
 
         data.load_all(mock_app)