Merge default feature flags and user defined feature flags

- Rename the default feature flags key in `config.py` to DEFAULT_FEATURE_FLAGS
- Merge default feature flags with user defined ones allowing the latter to overwrite the former
- Expose feature_flags for both server and client to use
- Add a utility method for checking whether a feature flag is on on server side

CONTRIBUTING.md

@@ -410,6 +410,10 @@ export enum FeatureFlag {
 }
 ```
 
+`superset/config.py` contains `DEFAULT_FEATURE_FLAGS` which will be overwritten by
+those specified under FEATURE_FLAGS in `superset_config.py`. For example, `DEFAULT_FEATURE_FLAGS = { 'FOO': True, 'BAR': False }` in `superset/config.py` and `FEATURE_FLAGS = { 'BAR': True, 'BAZ': True }` in `superset_config.py` will result
+in combined feature flags of `{ 'FOO': True, 'BAR': True, 'BAZ': True }`.
+
 ## Linting
 
 Lint the project with:

superset/__init__.py

@@ -208,6 +208,10 @@ security_manager = appbuilder.sm
 
 results_backend = app.config.get('RESULTS_BACKEND')
 
+# Merge user defined feature flags with default feature flags
+feature_flags = app.config.get('DEFAULT_FEATURE_FLAGS')
+feature_flags.update(app.config.get('FEATURE_FLAGS') or {})
+
 # Registering sources
 module_datasource_map = app.config.get('DEFAULT_MODULE_DS_MAP')
 module_datasource_map.update(app.config.get('ADDITIONAL_MODULE_DS_MAP'))

superset/config.py

@@ -186,9 +186,12 @@ LANGUAGES = {
 # ---------------------------------------------------
 # Feature flags
 # ---------------------------------------------------
-# Feature flags that are on by default go here. Their
-# values can be overridden by those in super_config.py
-FEATURE_FLAGS = {}
+# Feature flags that are set by default go here. Their values can be
+# overwritten by those specified under FEATURE_FLAGS in super_config.py
+# For example, DEFAULT_FEATURE_FLAGS = { 'FOO': True, 'BAR': False } here
+# and FEATURE_FLAGS = { 'BAR': True, 'BAZ': True } in superset_config.py
+# will result in combined feature flags of { 'FOO': True, 'BAR': True, 'BAZ': True }
+DEFAULT_FEATURE_FLAGS = {}
 
 # ---------------------------------------------------
 # Image and file configuration

superset/utils/feature_flags.py

@@ -0,0 +1,25 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+# pylint: disable=C,R,W
+from superset import feature_flags
+
+
+def is_feature_enabled(feature):
+    """
+    Utility function for checking whether a feature is turned on
+    """
+    return feature_flags.get(feature)

superset/views/base.py

@@ -31,7 +31,7 @@ from flask_babel import lazy_gettext as _
 import simplejson as json
 import yaml
 
-from superset import conf, db, security_manager
+from superset import conf, db, feature_flags, security_manager
 from superset.exceptions import SupersetException, SupersetSecurityException
 from superset.translations.utils import get_language_pack
 from superset.utils import core as utils
@@ -157,7 +157,7 @@ class BaseSupersetView(BaseView):
             'conf': {k: conf.get(k) for k in FRONTEND_CONF_KEYS},
             'locale': locale,
             'language_pack': get_language_pack(locale),
-            'feature_flags': conf.get('FEATURE_FLAGS'),
+            'feature_flags': feature_flags,
         }
 
 

tests/utils_tests.py

@@ -39,6 +39,7 @@ from superset.utils.core import (
     zlib_compress,
     zlib_decompress_to_string,
 )
+from superset.utils.feature_flags import is_feature_enabled
 
 
 def mock_parse_human_datetime(s):
@@ -756,3 +757,11 @@ class UtilsTestCase(unittest.TestCase):
         }
         convert_legacy_filters_into_adhoc(form_data)
         self.assertEquals(form_data, expected)
+
+    @patch.dict('superset.feature_flags', {'FOO': True}, clear=True)
+    def test_existing_feature_flags(self):
+        self.assertTrue(is_feature_enabled('FOO'))
+
+    @patch.dict('superset.feature_flags', {}, clear=True)
+    def test_nonexistent_feature_flags(self):
+        self.assertFalse(is_feature_enabled('FOO'))