Merge pull request #11 from iromli/inline-featureflags

Add custom handler to add inline feature flags

docs/contrib.rst

@@ -30,3 +30,55 @@ It will automatically create a table to store your flags in, or you can override
 
     ff.add_handler(SQLAlchemyFeatureFlags(db, model=MyModel))
 
+
+Inline
+------
+
+``InlineFeatureFlag`` checks for any flag in app's config with `FEATURE_FLAGS_X` format,
+where `X` is the name of a specific feature.
+
+The difference between this handler and default handler is,
+instead of defining flag in ``dict``-style:
+
+.. sourcecode:: python
+
+    FEATURE_FLAGS {
+        'finished': False,
+    }
+
+the feature name must use uppercased plain string:
+
+.. sourcecode:: python
+
+    FEATURE_FLAGS_FINISHED = False
+
+The motivation behind this inline handler is to interopt with other Flask extensions
+that rely on environment variable, e.g. `Flask-AppConfig <https://pypi.python.org/pypi/flask-appconfig>`_.
+
+Usage
++++++
+
+A typical usage is as trivial as the following snippet:
+
+.. sourcecode:: python
+
+    from flask import Flask
+    import flask_featureflags as feature_flags
+    from flask_featureflags.contrib.inline import InlineFeatureFlag
+
+    # feature flags config
+    FEATURE_FLAGS_FINISHED = False
+
+    app = Flask(__name__)
+    app.config.from_object(__name__)
+    ff = feature_flags.FeatureFlag(app)
+    ff.add_handler(InlineFeatureFlag())
+
+    @app.route("/")
+    def index():
+        return "Homepage"
+
+    @app.route("/new")
+    @feature_flags.is_active_feature("FINISHED", redirect_to="/")
+    def new():
+        return "New feature"

flask_featureflags/contrib/inline/__init__.py

@@ -0,0 +1,18 @@
+from flask import current_app
+from flask.ext.featureflags import FEATURE_FLAGS_CONFIG
+from flask.ext.featureflags import NoFeatureFlagFound
+from flask.ext.featureflags import log
+
+
+class InlineFeatureFlag(object):
+  def __call__(self, feature):
+    if not current_app:
+      log.warn(u"Got a request to check for {feature} but we're outside the request context. Returning False".format(feature=feature))
+      return False
+
+    feature_cfg = "{prefix}_{feature}".format(prefix=FEATURE_FLAGS_CONFIG, feature=feature)
+
+    try:
+      return current_app.config[feature_cfg]
+    except KeyError:
+      raise NoFeatureFlagFound()

tests/contrib/test_inline_handler.py

@@ -0,0 +1,42 @@
+import unittest
+
+import flask_featureflags as feature_flags
+from flask_featureflags.contrib.inline import InlineFeatureFlag
+
+from tests.fixtures import app
+from tests.fixtures import feature_setup
+
+
+inline_feature_flag = InlineFeatureFlag()
+
+
+class InlineFeatureFlagTest(unittest.TestCase):
+  @classmethod
+  def setUpClass(cls):
+    feature_setup.add_handler(inline_feature_flag)
+
+  @classmethod
+  def tearDownClass(cls):
+    feature_setup.clear_handlers()
+
+  def setUp(self):
+    self.app_ctx = app.app_context()
+    self.app_ctx.push()
+    app.config["FEATURE_FLAGS_ACTIVE"] = True
+    app.config["FEATURE_FLAGS_INACTIVE"] = False
+
+  def tearDown(self):
+    self.app_ctx.pop()
+
+  def test_flag_active(self):
+    self.assertTrue(feature_flags.is_active("ACTIVE"))
+
+  def test_flag_inactive(self):
+    self.assertFalse(feature_flags.is_active("INACTIVE"))
+
+  def test_flag_not_found(self):
+    self.assertFalse(feature_flags.is_active("NOT_FOUND"))
+
+  def test_flag_not_found_raise_handler_exception(self):
+    self.assertRaises(feature_flags.NoFeatureFlagFound,
+                      inline_feature_flag, "NOT_FOUND")