[BD-21] Extract waffle_utils from edx-platform

.annotation_safe_list.yml

@@ -11,6 +11,12 @@ auth.Group:
   ".. no_pii:": "This model has no PII"
 auth.Permission:
   ".. no_pii:": "This model has no PII"
+waffle.Flag:
+  ".. no_pii:": "This model has no PII"
+waffle.Sample:
+  ".. no_pii:": "This model has no PII"
+waffle.Switch:
+  ".. no_pii:": "This model has no PII"
 auth.User:
   ".. pii:": "Contains username, password, and email address, must be retired in the consumer of this app"
   ".. pii_types:" : username, email_address, password

CHANGELOG.rst

@@ -11,9 +11,12 @@ Change Log
 
 .. There should always be an "Unreleased" section for changes pending release.
 
-Unreleased
-~~~~~~~~~~
+[1.0.0] - 2020-10-13
+~~~~~~~~~~~~~~~~~~~~
 
+* Fix missing ``module_name`` argument in ``SettingDictToggle`` constructor.
+* Extract waffle classes from edx-platform and move them here following ADR `#2 <docs/decisions/0002-application-toggle-state.rst>`__, `#3 <docs/decisions/0003-django-setting-toggles.rst>`__, `#4 <docs/decisions/0004-toggle-api.rst>`__. This does not introduce backward-incompatible changes, *yet*.
+* Fix pinned requirements and incorrect root url that overrode edx-platform's.
 
 [0.3.0] - 2020-09-23
 ~~~~~~~~~~~~~~~~~~~~

docs/decisions/0004-toggle-api.rst

@@ -18,7 +18,7 @@ Decision
 
 All implementation code should be moved to an ``internal`` module. The Public API will be exposed as follows in ``edx_toggles/toggles/__init__.py``::
 
-    from .internal import ...
+    from .internal.togglemodule import ...
 
 The benefits of this setup include:
 

edx_toggles/__init__.py

@@ -2,6 +2,6 @@
 Library and utilities for feature toggles.
 """
 
-__version__ = '0.3.0'
+__version__ = '1.0.0'
 
 default_app_config = 'edx_toggles.apps.TogglesConfig'  # pylint: disable=invalid-name

edx_toggles/tests/test_testutils.py

@@ -0,0 +1,96 @@
+"""
+Tests for waffle utils test utilities.
+"""
+
+
+import crum
+from django.test import TestCase
+from django.test.client import RequestFactory
+from edx_django_utils.cache import RequestCache
+
+from edx_toggles.toggles import WaffleFlag, WaffleFlagNamespace
+from edx_toggles.toggles.testutils import override_waffle_flag
+
+
+class OverrideWaffleFlagTests(TestCase):
+    """
+    Tests for the override_waffle_flag decorator/context manager.
+    """
+
+    def setUp(self):
+        super(OverrideWaffleFlagTests, self).setUp()
+        namespace_name = "test_namespace"
+        flag_name = "test_flag"
+        self.namespaced_flag_name = namespace_name + "." + flag_name
+        self.namespace = WaffleFlagNamespace(namespace_name)
+        self.waffle_flag = WaffleFlag(self.namespace, flag_name)
+
+        request = RequestFactory().request()
+        crum.set_current_request(request)
+        RequestCache.clear_all_namespaces()
+
+        self.addCleanup(crum.set_current_request, None)
+        self.addCleanup(RequestCache.clear_all_namespaces)
+
+    def temporarily_enable_flag(self):
+        """
+        Temporarily override flag.
+        """
+
+        @override_waffle_flag(self.waffle_flag, True)
+        def test_func():
+            """
+            Decorated test function.
+            """
+            self.assertTrue(self.waffle_flag.is_enabled())
+
+        test_func()
+
+    def test_override_waffle_flag_pre_cached(self):
+        # checks and caches the is_enabled value
+        self.assertFalse(self.waffle_flag.is_enabled())
+        # pylint: disable=protected-access
+        flag_cache = self.namespace._cached_flags
+        self.assertIn(self.namespaced_flag_name, flag_cache)
+
+        self.temporarily_enable_flag()
+
+        # test cached flag is restored
+        self.assertIn(self.namespaced_flag_name, flag_cache)
+        self.assertFalse(self.waffle_flag.is_enabled())
+
+    def test_override_waffle_flag_not_pre_cached(self):
+        # check that the flag is not yet cached
+        # pylint: disable=protected-access
+        flag_cache = self.namespace._cached_flags
+        self.assertNotIn(self.namespaced_flag_name, flag_cache)
+
+        self.temporarily_enable_flag()
+
+        # test cache is removed when no longer using decorator/context manager
+        self.assertNotIn(self.namespaced_flag_name, flag_cache)
+
+    def test_override_waffle_flag_as_context_manager(self):
+        self.assertFalse(self.waffle_flag.is_enabled())
+
+        with override_waffle_flag(self.waffle_flag, True):
+            self.assertTrue(self.waffle_flag.is_enabled())
+
+        self.assertFalse(self.waffle_flag.is_enabled())
+
+    def test_interlocked_overrides(self):
+        waffle_flag1 = self.waffle_flag
+        waffle_flag2 = WaffleFlag(self.namespace, waffle_flag1.flag_name + "2")
+        # pylint: disable=protected-access
+        self.namespace._cached_flags[waffle_flag2.namespaced_flag_name] = True
+
+        self.assertFalse(waffle_flag1.is_enabled())
+        self.assertTrue(waffle_flag2.is_enabled())
+
+        with override_waffle_flag(waffle_flag1, True):
+            with override_waffle_flag(waffle_flag2, False):
+                self.assertTrue(waffle_flag1.is_enabled())
+                self.assertFalse(waffle_flag2.is_enabled())
+
+        self.assertFalse(waffle_flag1.is_enabled())
+        self.assertTrue(waffle_flag2.is_enabled())

edx_toggles/tests/test_toggles.py

@@ -12,6 +12,7 @@ class SettingToggleTests(TestCase):
     """
     SettingToggle tests
     """
+
     def test_toggle_for_absent_setting(self):
         toggle1 = toggles.SettingToggle("NAME1", True)
         toggle2 = toggles.SettingToggle("NAME1", False)
@@ -36,9 +37,14 @@ class SettingDictToggleTests(TestCase):
     """
     SettingDictToggle tests
     """
+
     def test_toggle_for_absent_setting(self):
-        toggle1 = toggles.SettingDictToggle("NAME1", "key1", True)
-        toggle2 = toggles.SettingDictToggle("NAME2", "key2", False)
+        toggle1 = toggles.SettingDictToggle(
+            "NAME1", "key1", True, module_name="module1"
+        )
+        toggle2 = toggles.SettingDictToggle(
+            "NAME2", "key2", False, module_name="module1"
+        )
         self.assertTrue(toggle1.is_enabled())
         self.assertFalse(toggle2.is_enabled())
 
@@ -59,6 +65,7 @@ class ToggleInstancesTests(TestCase):
     """
     Class instance-tracking tests
     """
+
     def test_created_instances(self):
         toggle1 = toggles.SettingToggle("NAME1", default=False, module_name="module1")
         toggle2 = toggles.SettingToggle("NAME2", default=False, module_name="module2")
@@ -71,3 +78,22 @@ def test_deleted_instances_are_not_listed(self):
         toggles.SettingToggle("NAME1", default=False, module_name="module1")
         instances = toggles.SettingToggle.get_instances()
         self.assertEqual([], instances)
+
+
+class TestWaffleSwitch(TestCase):
+    """
+    Tests the WaffleSwitch.
+    """
+
+    NAMESPACE_NAME = "test_namespace"
+    WAFFLE_SWITCH_NAME = "test_switch_name"
+    TEST_NAMESPACE = toggles.WaffleSwitchNamespace(NAMESPACE_NAME)
+    WAFFLE_SWITCH = toggles.WaffleSwitch(TEST_NAMESPACE, WAFFLE_SWITCH_NAME, __name__)
+
+    def test_namespaced_switch_name(self):
+        """
+        Verify namespaced_switch_name returns the correct namespace switch name
+        """
+        expected = self.NAMESPACE_NAME + "." + self.WAFFLE_SWITCH_NAME
+        actual = self.WAFFLE_SWITCH.namespaced_switch_name
+        self.assertEqual(actual, expected)

edx_toggles/toggles/__init__.py

@@ -1,4 +1,5 @@
 """
 Expose public feature toggle API.
 """
-from .internal import SettingDictToggle, SettingToggle
+from .internal.setting_toggle import SettingDictToggle, SettingToggle
+from .internal.waffle import WaffleFlag, WaffleFlagNamespace, WaffleSwitch, WaffleSwitchNamespace

edx_toggles/toggles/internal/__init__.py

@@ -0,0 +1,4 @@
+"""
+This module includes all code related to feature toggles. Remember to import publicly available classes and functions
+in toggles/__init__.py.
+"""

edx_toggles/toggles/internal/base.py

@@ -0,0 +1,68 @@
+"""
+Feature toggle base classes
+"""
+
+from abc import ABC
+
+
+class BaseToggle(ABC):
+    """
+    This abstract base class exposes the basic API required by toggle classes. Toggle instances are tracked in the
+    ``_class_instances`` class method, which is exposed via the ``get_instances`` class method.
+    """
+
+    # Each child class should implement its own cache of class instances, for instance via WeakSet objects.
+    _class_instances = None
+
+    def __init__(self, name, default=False, module_name=""):
+        self.name = name
+        self.default = default
+        self.module_name = module_name
+        self._class_instances.add(self)
+
+    def is_enabled(self):
+        raise NotImplementedError
+
+    @classmethod
+    def get_instances(cls):
+        """
+        Return the list of class instances sorted by name.
+        """
+        return sorted(cls._class_instances, key=lambda instance: instance.name)
+
+
+class BaseNamespace(ABC):
+    """
+    A base class for a request cached namespace for waffle flags/switches.
+
+    An instance of this class represents a single namespace
+    (e.g. "course_experience"), and can be used to work with a set of
+    flags or switches that will all share this namespace.
+    """
+
+    def __init__(self, name, log_prefix=None):
+        """
+        Initializes the waffle namespace instance.
+
+        Arguments:
+            name (String): Namespace string appended to start of all waffle
+                flags and switches (e.g. "grades")
+            log_prefix (String): Optional string to be appended to log messages
+                (e.g. "Grades: "). Defaults to ''.
+
+        """
+        assert name, "The name is required."
+        self.name = name
+        self.log_prefix = log_prefix if log_prefix else ""
+
+    def _namespaced_name(self, setting_name):
+        """
+        Returns the namespaced name of the waffle switch/flag.
+
+        For example, the namespaced name of a waffle switch/flag would be:
+            my_namespace.my_setting_name
+
+        Arguments:
+            setting_name (String): The name of the flag or switch.
+        """
+        return "{}.{}".format(self.name, setting_name)