refactor: A Better API for Derived Settings

cms/envs/common.py

@@ -144,7 +144,7 @@
     get_theme_base_dirs_from_settings
 )
 from openedx.core.lib.license import LicenseMixin
-from openedx.core.lib.derived import derived, derived_collection_entry
+from openedx.core.lib.derived import Derived
 from openedx.core.release import doc_version
 
 # pylint: enable=useless-suppression
@@ -740,7 +740,7 @@
         # Don't look for template source files inside installed applications.
         'APP_DIRS': False,
         # Instead, look for template source files in these dirs.
-        'DIRS': _make_mako_template_dirs,
+        'DIRS': Derived(_make_mako_template_dirs),
         # Options specific to this backend.
         'OPTIONS': {
             'loaders': (
@@ -759,7 +759,7 @@
         'NAME': 'mako',
         'BACKEND': 'common.djangoapps.edxmako.backend.Mako',
         'APP_DIRS': False,
-        'DIRS': _make_mako_template_dirs,
+        'DIRS': Derived(_make_mako_template_dirs),
         'OPTIONS': {
             'context_processors': CONTEXT_PROCESSORS,
             'debug': False,
@@ -778,8 +778,6 @@
         }
     },
 ]
-derived_collection_entry('TEMPLATES', 0, 'DIRS')
-derived_collection_entry('TEMPLATES', 1, 'DIRS')
 DEFAULT_TEMPLATE_ENGINE = TEMPLATES[0]
 
 #################################### AWS #######################################
@@ -825,8 +823,7 @@
 # Warning: Must have trailing slash to activate correct logout view
 # (auth_backends, not LMS user_authn)
 FRONTEND_LOGOUT_URL = '/logout/'
-FRONTEND_REGISTER_URL = lambda settings: settings.LMS_ROOT_URL + '/register'
-derived('FRONTEND_REGISTER_URL')
+FRONTEND_REGISTER_URL = Derived(lambda settings: settings.LMS_ROOT_URL + '/register')
 
 LMS_ENROLLMENT_API_PATH = "/api/enrollment/v1/"
 ENTERPRISE_API_URL = LMS_INTERNAL_ROOT_URL + '/enterprise/api/v1/'
@@ -1316,8 +1313,7 @@
 STATICI18N_FILENAME_FUNCTION = 'statici18n.utils.legacy_filename'
 STATICI18N_ROOT = PROJECT_ROOT / "static"
 
-LOCALE_PATHS = _make_locale_paths
-derived('LOCALE_PATHS')
+LOCALE_PATHS = Derived(_make_locale_paths)
 
 # Messages
 MESSAGE_STORAGE = 'django.contrib.messages.storage.session.SessionStorage'
@@ -2087,10 +2083,9 @@
 # See annotations in lms/envs/common.py for details.
 RETIRED_EMAIL_DOMAIN = 'retired.invalid'
 # See annotations in lms/envs/common.py for details.
-RETIRED_USERNAME_FMT = lambda settings: settings.RETIRED_USERNAME_PREFIX + '{}'
+RETIRED_USERNAME_FMT = Derived(lambda settings: settings.RETIRED_USERNAME_PREFIX + '{}')
 # See annotations in lms/envs/common.py for details.
-RETIRED_EMAIL_FMT = lambda settings: settings.RETIRED_EMAIL_PREFIX + '{}@' + settings.RETIRED_EMAIL_DOMAIN
-derived('RETIRED_USERNAME_FMT', 'RETIRED_EMAIL_FMT')
+RETIRED_EMAIL_FMT = Derived(lambda settings: settings.RETIRED_EMAIL_PREFIX + '{}@' + settings.RETIRED_EMAIL_DOMAIN)
 # See annotations in lms/envs/common.py for details.
 RETIRED_USER_SALTS = ['abc', '123']
 # See annotations in lms/envs/common.py for details.
@@ -2367,13 +2362,12 @@
 ############## Settings for Studio Context Sensitive Help ##############
 
 HELP_TOKENS_INI_FILE = REPO_ROOT / "cms" / "envs" / "help_tokens.ini"
-HELP_TOKENS_LANGUAGE_CODE = lambda settings: settings.LANGUAGE_CODE
-HELP_TOKENS_VERSION = lambda settings: doc_version()
+HELP_TOKENS_LANGUAGE_CODE = Derived(lambda settings: settings.LANGUAGE_CODE)
+HELP_TOKENS_VERSION = Derived(lambda settings: doc_version())
 HELP_TOKENS_BOOKS = {
     'learner': 'https://edx.readthedocs.io/projects/open-edx-learner-guide',
     'course_author': 'https://edx.readthedocs.io/projects/open-edx-building-and-running-a-course',
 }
-derived('HELP_TOKENS_LANGUAGE_CODE', 'HELP_TOKENS_VERSION')
 
 # Used with Email sending
 RETRY_ACTIVATION_EMAIL_MAX_ATTEMPTS = 5
@@ -2876,15 +2870,15 @@ def _should_send_learning_badge_events(settings):
     },
     'org.openedx.content_authoring.xblock.published.v1': {
         'course-authoring-xblock-lifecycle':
-            {'event_key_field': 'xblock_info.usage_key', 'enabled': _should_send_xblock_events},
+            {'event_key_field': 'xblock_info.usage_key', 'enabled': Derived(_should_send_xblock_events)},
     },
     'org.openedx.content_authoring.xblock.deleted.v1': {
         'course-authoring-xblock-lifecycle':
-            {'event_key_field': 'xblock_info.usage_key', 'enabled': _should_send_xblock_events},
+            {'event_key_field': 'xblock_info.usage_key', 'enabled': Derived(_should_send_xblock_events)},
     },
     'org.openedx.content_authoring.xblock.duplicated.v1': {
         'course-authoring-xblock-lifecycle':
-            {'event_key_field': 'xblock_info.usage_key', 'enabled': _should_send_xblock_events},
+            {'event_key_field': 'xblock_info.usage_key', 'enabled': Derived(_should_send_xblock_events)},
     },
     # LMS events. These have to be copied over here because lms.common adds some derived entries as well,
     # and the derivation fails if the keys are missing. If we ever remove the import of lms.common, we can remove these.
@@ -2899,38 +2893,17 @@ def _should_send_learning_badge_events(settings):
     "org.openedx.learning.course.passing.status.updated.v1": {
         "learning-badges-lifecycle": {
             "event_key_field": "course_passing_status.course.course_key",
-            "enabled": _should_send_learning_badge_events,
+            "enabled": Derived(_should_send_learning_badge_events),
         },
     },
     "org.openedx.learning.ccx.course.passing.status.updated.v1": {
         "learning-badges-lifecycle": {
             "event_key_field": "course_passing_status.course.ccx_course_key",
-            "enabled": _should_send_learning_badge_events,
+            "enabled": Derived(_should_send_learning_badge_events),
         },
     },
 }
 
-
-derived_collection_entry('EVENT_BUS_PRODUCER_CONFIG', 'org.openedx.content_authoring.xblock.published.v1',
-                         'course-authoring-xblock-lifecycle', 'enabled')
-derived_collection_entry('EVENT_BUS_PRODUCER_CONFIG', 'org.openedx.content_authoring.xblock.duplicated.v1',
-                         'course-authoring-xblock-lifecycle', 'enabled')
-derived_collection_entry('EVENT_BUS_PRODUCER_CONFIG', 'org.openedx.content_authoring.xblock.deleted.v1',
-                         'course-authoring-xblock-lifecycle', 'enabled')
-
-derived_collection_entry(
-    "EVENT_BUS_PRODUCER_CONFIG",
-    "org.openedx.learning.course.passing.status.updated.v1",
-    "learning-badges-lifecycle",
-    "enabled",
-)
-derived_collection_entry(
-    "EVENT_BUS_PRODUCER_CONFIG",
-    "org.openedx.learning.ccx.course.passing.status.updated.v1",
-    "learning-badges-lifecycle",
-    "enabled",
-)
-
 ################### Authoring API ######################
 
 # This affects the Authoring API swagger docs but not the legacy swagger docs under /api-docs/.

lms/envs/common.py

@@ -69,7 +69,7 @@
     get_themes_unchecked,
     get_theme_base_dirs_from_settings
 )
-from openedx.core.lib.derived import derived, derived_collection_entry
+from openedx.core.lib.derived import Derived
 from openedx.core.release import doc_version
 from lms.djangoapps.lms_xblock.mixin import LmsBlockMixin
 
@@ -1395,7 +1395,7 @@ def _make_mako_template_dirs(settings):
         # Don't look for template source files inside installed applications.
         'APP_DIRS': False,
         # Instead, look for template source files in these dirs.
-        'DIRS': _make_mako_template_dirs,
+        'DIRS': Derived(_make_mako_template_dirs),
         # Options specific to this backend.
         'OPTIONS': {
             'context_processors': CONTEXT_PROCESSORS,
@@ -1404,7 +1404,6 @@ def _make_mako_template_dirs(settings):
         }
     },
 ]
-derived_collection_entry('TEMPLATES', 1, 'DIRS')
 DEFAULT_TEMPLATE_ENGINE = TEMPLATES[0]
 DEFAULT_TEMPLATE_ENGINE_DIRS = DEFAULT_TEMPLATE_ENGINE['DIRS'][:]
 
@@ -1734,7 +1733,7 @@ def _make_mako_template_dirs(settings):
                     'DOC_STORE_CONFIG': DOC_STORE_CONFIG,
                     'OPTIONS': {
                         'default_class': 'xmodule.hidden_block.HiddenBlock',
-                        'fs_root': lambda settings: settings.DATA_DIR,
+                        'fs_root': Derived(lambda settings: settings.DATA_DIR),
                         'render_template': 'common.djangoapps.edxmako.shortcuts.render_to_string',
                     }
                 },
@@ -1744,7 +1743,7 @@ def _make_mako_template_dirs(settings):
                     'DOC_STORE_CONFIG': DOC_STORE_CONFIG,
                     'OPTIONS': {
                         'default_class': 'xmodule.hidden_block.HiddenBlock',
-                        'fs_root': lambda settings: settings.DATA_DIR,
+                        'fs_root': Derived(lambda settings: settings.DATA_DIR),
                         'render_template': 'common.djangoapps.edxmako.shortcuts.render_to_string',
                     }
                 }
@@ -2054,8 +2053,7 @@ def _make_locale_paths(settings):  # pylint: disable=missing-function-docstring
         for locale_path in settings.COMPREHENSIVE_THEME_LOCALE_PATHS:
             locale_paths += (path(locale_path), )
     return locale_paths
-LOCALE_PATHS = _make_locale_paths
-derived('LOCALE_PATHS')
+LOCALE_PATHS = Derived(_make_locale_paths)
 
 # Messages
 MESSAGE_STORAGE = 'django.contrib.messages.storage.session.SessionStorage'
@@ -4661,13 +4659,12 @@ def _make_locale_paths(settings):  # pylint: disable=missing-function-docstring
 ############## Settings for LMS Context Sensitive Help ##############
 
 HELP_TOKENS_INI_FILE = REPO_ROOT / "lms" / "envs" / "help_tokens.ini"
-HELP_TOKENS_LANGUAGE_CODE = lambda settings: settings.LANGUAGE_CODE
-HELP_TOKENS_VERSION = lambda settings: doc_version()
+HELP_TOKENS_LANGUAGE_CODE = Derived(lambda settings: settings.LANGUAGE_CODE)
+HELP_TOKENS_VERSION = Derived(lambda settings: doc_version())
 HELP_TOKENS_BOOKS = {
     'learner': 'https://edx.readthedocs.io/projects/open-edx-learner-guide',
     'course_author': 'https://edx.readthedocs.io/projects/open-edx-building-and-running-a-course',
 }
-derived('HELP_TOKENS_LANGUAGE_CODE', 'HELP_TOKENS_VERSION')
 
 ############## OPEN EDX ENTERPRISE SERVICE CONFIGURATION ######################
 # The Open edX Enterprise service is currently hosted via the LMS container/process.
@@ -4955,14 +4952,13 @@ def _make_locale_paths(settings):  # pylint: disable=missing-function-docstring
 # .. setting_description: Set the format a retired user username field gets transformed into, where {}
 #     is replaced with the hash of the original username. This is a derived setting that depends on
 #     RETIRED_USERNAME_PREFIX value.
-RETIRED_USERNAME_FMT = lambda settings: settings.RETIRED_USERNAME_PREFIX + '{}'
+RETIRED_USERNAME_FMT = Derived(lambda settings: settings.RETIRED_USERNAME_PREFIX + '{}'),
 # .. setting_name: RETIRED_EMAIL_FMT
 # .. setting_default: retired__user_{}@retired.invalid
 # .. setting_description: Set the format a retired user email field gets transformed into, where {} is
 #     replaced with the hash of the original email. This is a derived setting that depends on
 #     RETIRED_EMAIL_PREFIX and RETIRED_EMAIL_DOMAIN values.
-RETIRED_EMAIL_FMT = lambda settings: settings.RETIRED_EMAIL_PREFIX + '{}@' + settings.RETIRED_EMAIL_DOMAIN
-derived('RETIRED_USERNAME_FMT', 'RETIRED_EMAIL_FMT')
+RETIRED_EMAIL_FMT = Derived(lambda settings: settings.RETIRED_EMAIL_PREFIX + '{}@' + settings.RETIRED_EMAIL_DOMAIN),
 # .. setting_name: RETIRED_USER_SALTS
 # .. setting_default: ['abc', '123']
 # .. setting_description: Set a list of salts used for hashing usernames and emails on users retirement.
@@ -5450,11 +5446,11 @@ def _should_send_learning_badge_events(settings):
 EVENT_BUS_PRODUCER_CONFIG = {
     'org.openedx.learning.certificate.created.v1': {
         'learning-certificate-lifecycle':
-            {'event_key_field': 'certificate.course.course_key', 'enabled': _should_send_certificate_events},
+            {'event_key_field': 'certificate.course.course_key', 'enabled': Derived(_should_send_certificate_events)},
     },
     'org.openedx.learning.certificate.revoked.v1': {
         'learning-certificate-lifecycle':
-            {'event_key_field': 'certificate.course.course_key', 'enabled': _should_send_certificate_events},
+            {'event_key_field': 'certificate.course.course_key', 'enabled': Derived(_should_send_certificate_events)},
     },
     'org.openedx.learning.course.unenrollment.completed.v1': {
         'course-unenrollment-lifecycle':
@@ -5516,33 +5512,16 @@ def _should_send_learning_badge_events(settings):
     "org.openedx.learning.course.passing.status.updated.v1": {
         "learning-badges-lifecycle": {
             "event_key_field": "course_passing_status.course.course_key",
-            "enabled": _should_send_learning_badge_events,
+            "enabled": Derived(_should_send_learning_badge_events),
         },
     },
     "org.openedx.learning.ccx.course.passing.status.updated.v1": {
         "learning-badges-lifecycle": {
             "event_key_field": "course_passing_status.course.ccx_course_key",
-            "enabled": _should_send_learning_badge_events,
+            "enabled": Derived(_should_send_learning_badge_events),
         },
     },
 }
-derived_collection_entry('EVENT_BUS_PRODUCER_CONFIG', 'org.openedx.learning.certificate.created.v1',
-                         'learning-certificate-lifecycle', 'enabled')
-derived_collection_entry('EVENT_BUS_PRODUCER_CONFIG', 'org.openedx.learning.certificate.revoked.v1',
-                         'learning-certificate-lifecycle', 'enabled')
-
-derived_collection_entry(
-    "EVENT_BUS_PRODUCER_CONFIG",
-    "org.openedx.learning.course.passing.status.updated.v1",
-    "learning-badges-lifecycle",
-    "enabled",
-)
-derived_collection_entry(
-    "EVENT_BUS_PRODUCER_CONFIG",
-    "org.openedx.learning.ccx.course.passing.status.updated.v1",
-    "learning-badges-lifecycle",
-    "enabled",
-)
 
 BEAMER_PRODUCT_ID = ""
 

lms/envs/docs/README.rst

@@ -56,8 +56,7 @@ For example:
             for locale_path in settings.COMPREHENSIVE_THEME_LOCALE_PATHS:
                 locale_paths += (path(locale_path), )
         return locale_paths
-    LOCALE_PATHS = _make_locale_paths
-    derived('LOCALE_PATHS')
+    LOCALE_PATHS = Derived(_make_locale_paths)
 
 In this case, ``LOCALE_PATHS`` will be defined correctly at the end of the
 settings module parsing no matter what ``REPO_ROOT``,
@@ -92,7 +91,6 @@ when nested within each other:
             'NAME': 'mako',
             'BACKEND': 'common.djangoapps.edxmako.backend.Mako',
             'APP_DIRS': False,
-            'DIRS': _make_mako_template_dirs,
+            'DIRS': Derived(_make_mako_template_dirs),
         },
     ]
-    derived_collection_entry('TEMPLATES', 1, 'DIRS')

lms/envs/production.py

@@ -349,17 +349,6 @@ def get_env_setting(setting):
 # use the one from common.py
 MODULESTORE = convert_module_store_setting_if_needed(_YAML_TOKENS.get('MODULESTORE', MODULESTORE))
 
-# After conversion above, the modulestore will have a "stores" list with all defined stores, for all stores, add the
-# fs_root entry to derived collection so that if it's a callable it can be resolved.  We need to do this because the
-# `derived_collection_entry` takes an exact index value but the config file might have overridden the number of stores
-# and so we can't be sure that the 2 we define in common.py will be there when we try to derive settings.  This could
-# lead to exceptions being thrown when the `derive_settings` call later in this file tries to update settings.  We call
-# the derived_collection_entry function here to ensure that we update the fs_root for any callables that remain after
-# we've updated the MODULESTORE setting from our config file.
-for idx, store in enumerate(MODULESTORE['default']['OPTIONS']['stores']):
-    if 'OPTIONS' in store and 'fs_root' in store["OPTIONS"]:
-        derived_collection_entry('MODULESTORE', 'default', 'OPTIONS', 'stores', idx, 'OPTIONS', 'fs_root')
-
 BROKER_URL = "{}://{}:{}@{}/{}".format(CELERY_BROKER_TRANSPORT,
                                        CELERY_BROKER_USER,
                                        CELERY_BROKER_PASSWORD,

mypy.ini

@@ -12,6 +12,7 @@ files =
     openedx/core/djangoapps/content_staging,
     openedx/core/djangoapps/content_libraries,
     openedx/core/djangoapps/xblock,
+    openedx/core/lib/derived.py,
     openedx/core/types,
     openedx/core/djangoapps/content_tagging,
     xmodule/util/keys.py,

openedx/core/lib/derived.py

@@ -4,71 +4,121 @@
 other settings have been set. The derived setting can also be overridden by setting the
 derived setting to an actual value.
 """
+from __future__ import annotations
 
+import re
 import sys
+import types
+import typing as t
 
-# Global list holding all settings which will be derived.
-__DERIVED = []
 
+Settings: t.TypeAlias = types.ModuleType
 
-def derived(*settings):
+
+T = t.TypeVar('T')
+
+
+class Derived(t.Generic[T]):
     """
-    Registers settings which are derived from other settings.
-    Can be called multiple times to add more derived settings.
+    A temporary Django setting value, defined with a function which generates the setting's eventual value.
 
-    Args:
-        settings (str): Setting names to register.
+    Said function (`calculate_value`) should accept a Django settings module, and return a calculated value.
+
+    To ensure that application code does not encounter an instance of this class in your settings, be sure to call
+    `derive_settings` somewhere in your terminal settings file.
     """
-    __DERIVED.extend(settings)
+    def __init__(self, calculate_value: t.Callable[[Settings], T]):
+        self.calculate_value = calculate_value
 
 
-def derived_collection_entry(collection_name, *accessors):
+def derive_settings(module_name: str) -> None:
     """
-    Registers a setting which is a dictionary or list and needs a derived value for a particular entry.
-    Can be called multiple times to add more derived settings.
+    In the Django settings module at `module_name`, replace `Derived` values with their cacluated values.
 
-    Args:
-        collection_name (str): Name of setting which contains a dictionary or list.
-        accessors (int|str): Sequence of dictionary keys and list indices in the collection (and
-            collections within it) leading to the value which will be derived.
-            For example: 0, 'DIRS'.
+    The replacement happens recursively for any values or containers defined by a Django setting name (which is: an
+    uppercase top-level variable name which is not prefixed by an underscore). Within containers,
     """
-    __DERIVED.append((collection_name, accessors))
+    module = sys.modules[module_name]
+    _derive_dict(module, vars(module), key_filter=_key_is_a_setting_name)
+
+
+_SETTING_NAME_REGEX = re.compile(r'^[A-Z][A-Z0-9_]*$')
+
+
+def _key_is_a_setting_name(key: str) -> bool:
+    return bool(_SETTING_NAME_REGEX.match(key))
 
 
-def derive_settings(module_name):
+def _match_every_key(_key: str) -> bool:
+    return True
+
+
+def _derive_recursively(settings: Settings, value: t.Any) -> t.Any:
     """
-    Derives all registered settings and sets them onto a particular module.
-    Skips deriving settings that are set to a value.
+    Recursively evaluate `Derive` objects` in `value` and any child containers. Return the evaluated version of `value`.
 
-    Args:
-        module_name (str): Name of module to which the derived settings will be added.
+    * If `value` is a `Derive` object, then use `settings` to calculate and return its value.
+    * If `value` is a mutable container, then recursively evaluate it in-place.
+    * If `value` is an immutable container, then recursively evalute a shallow copy of it.
+      Keep in mind that immutable containers (particularly: tuples) can contain mutable containers. In such a case, the
+      original and shallow-copied mutable containers will both reference the same child mutable container object.
     """
-    module = sys.modules[module_name]
-    for derived in __DERIVED:  # lint-amnesty, pylint: disable=redefined-outer-name
-        if isinstance(derived, str):
-            setting = getattr(module, derived)
-            if callable(setting):
-                setting_val = setting(module)
-                setattr(module, derived, setting_val)
-        elif isinstance(derived, tuple):
-            # If a tuple, two elements are expected - else ignore.
-            if len(derived) == 2:
-                # The first element is the name of the attribute which is expected to be a dictionary or list.
-                # The second element is a list of string keys in that dictionary leading to a derived setting.
-                collection = getattr(module, derived[0])
-                accessors = derived[1]
-                for accessor in accessors[:-1]:
-                    collection = collection[accessor]
-                setting = collection[accessors[-1]]
-                if callable(setting):
-                    setting_val = setting(module)
-                    collection[accessors[-1]] = setting_val
-
-
-def clear_for_tests():
-    """
-    Clears all settings to be derived. For tests only.
-    """
-    global __DERIVED
-    __DERIVED = []
+    if isinstance(value, Derived):
+        return value.calculate_value(settings)
+    elif isinstance(value, dict):
+        return _derive_dict(settings, value)
+    elif isinstance(value, list):
+        return _derive_list(settings, value)
+    elif isinstance(value, tuple):
+        return _derive_tuple(settings, value)
+    elif isinstance(value, frozenset):
+        return _derive_frozenset(settings, value)
+    else:
+        return value
+
+
+def _derive_dict(settings: Settings, the_dict: dict, key_filter: t.Callable[[str], bool] = _match_every_key) -> dict:
+    """
+    Recursively evaluate `Derive` objects in `the_dict` and any child containers. Modifies `the_dict` in place.
+
+    Optionally takes a `key_filter`. Items that do not match the provided `key_filter` will be left alone.
+    """
+    for key, value in the_dict.items():
+        if key_filter(key):
+            the_dict[key] = _derive_recursively(settings, value)
+    return the_dict
+
+
+def _derive_list(settings: Settings, the_list: list) -> list:
+    """
+    Recursively evaluate `Derive` objects in `the_list` and any child containers. Modifies `the_list` in place.
+    """
+    for ix in range(len(the_list)):
+        the_list[ix] = _derive_recursively(settings, the_list[ix])
+    return the_list
+
+
+def _derive_tuple(settings: Settings, tup: tuple) -> tuple:
+    """
+    Recursively evaluate `Derive` objects in `tup` and any child containers. Returns a shallow copy of `tup`.
+    """
+    return tuple(_derive_recursively(settings, item) for item in tup)
+
+
+def _derive_set(settings: Settings, the_set: set) -> set:
+    """
+    Recursively evaluate `Derive` objects in `the_set` and any child containers. Modifies `the_set` in-place.
+    """
+    for original in the_set:
+        derived = _derive_recursively(settings, original)
+        if derived != original:
+            the_set.remove(original)
+            the_set.add(derived)
+    return the_set
+
+
+def _derive_frozenset(settings: Settings, the_set: frozenset) -> frozenset:
+    """
+    Recursively evaluate `Derive` objects in `the_set` and any child containers. Returns a shallow copy of `the_set`.
+    """
+    return frozenset(_derive_recursively(settings, item) for item in the_set)

openedx/core/lib/tests/test_derived.py

@@ -5,7 +5,7 @@
 
 import sys
 from unittest import TestCase
-from openedx.core.lib.derived import derived, derived_collection_entry, derive_settings, clear_for_tests
+from openedx.core.lib.derived import Derived, derive_settings
 
 
 class TestDerivedSettings(TestCase):
@@ -14,18 +14,14 @@ class TestDerivedSettings(TestCase):
     """
     def setUp(self):
         super().setUp()
-        clear_for_tests()
         self.module = sys.modules[__name__]
         self.module.SIMPLE_VALUE = 'paneer'
-        self.module.DERIVED_VALUE = lambda settings: 'mutter ' + settings.SIMPLE_VALUE
-        self.module.ANOTHER_DERIVED_VALUE = lambda settings: settings.DERIVED_VALUE + ' with naan'
+        self.module.DERIVED_VALUE = Derived(lambda settings: 'mutter ' + settings.SIMPLE_VALUE)
+        self.module.ANOTHER_DERIVED_VALUE = Derived(lambda settings: settings.DERIVED_VALUE + ' with naan')
         self.module.UNREGISTERED_DERIVED_VALUE = lambda settings: settings.SIMPLE_VALUE + ' is cheese'
-        derived('DERIVED_VALUE', 'ANOTHER_DERIVED_VALUE')
         self.module.DICT_VALUE = {}
-        self.module.DICT_VALUE['test_key'] = lambda settings: settings.DERIVED_VALUE * 3
-        derived_collection_entry('DICT_VALUE', 'test_key')
-        self.module.DICT_VALUE['list_key'] = ['not derived', lambda settings: settings.DERIVED_VALUE]
-        derived_collection_entry('DICT_VALUE', 'list_key', 1)
+        self.module.DICT_VALUE['test_key'] = Derived(lambda settings: settings.DERIVED_VALUE * 3)
+        self.module.DICT_VALUE['list_key'] = ['not derived', Derived(lambda settings: settings.DERIVED_VALUE)]
 
     def test_derived_settings_are_derived(self):
         derive_settings(__name__)

xmodule/modulestore/modulestore_settings.py

@@ -6,6 +6,8 @@
 import copy
 import warnings
 
+from openedx.core.lib.derived import Derived
+
 
 def convert_module_store_setting_if_needed(module_store_setting):
     """