SettingsService for accessing server-wide settings from XBlock

cms/djangoapps/contentstore/views/preview.py

@@ -15,6 +15,7 @@ from xmodule.contentstore.django import contentstore
 from xmodule.error_module import ErrorDescriptor
 from xmodule.exceptions import NotFoundError, ProcessingError
 from xmodule.library_tools import LibraryToolsService
+from xmodule.services import SettingsService
 from xmodule.modulestore.django import modulestore, ModuleI18nService
 from opaque_keys.edx.keys import UsageKey
 from opaque_keys.edx.locator import LibraryUsageLocator
@@ -191,6 +192,7 @@ def _preview_module_system(request, descriptor, field_data):
             "i18n": ModuleI18nService(),
             "field-data": field_data,
             "library_tools": LibraryToolsService(modulestore()),
+            "settings": SettingsService(),
             "user": DjangoXBlockUserService(request.user),
         },
     )

common/lib/xmodule/xmodule/services.py

+"""
+Module contains various XModule/XBlock services
+"""
+from django.conf import settings
+
+
+class SettingsService(object):
+    """
+    Allows server-wide configuration of XBlocks on a per-type basis
+
+    XBlock settings are read from XBLOCK_SETTINGS settings key. Each XBlock is allowed access
+    to single settings bucket. Bucket is determined by this service using the following rules:
+
+    * Value of SettingsService.xblock_settings_bucket_selector is examined. If XBlock have attribute/property
+    with the name of that value this attribute/property is read to get the bucket key (e.g. if XBlock have
+    `block_settings_key = 'my_block_settings'`, bucket key would be 'my_block_settings').
+    * Otherwise, XBlock class name is used
+
+    Service is content-agnostic: it just returns whatever happen to be in the settings bucket (technically, it returns
+    the bucket itself).
+
+    If `default` argument is specified it is returned if:
+    * There are no XBLOCK_SETTINGS setting
+    * XBLOCK_SETTINGS is empty
+    * XBLOCK_SETTINGS does not contain settings bucket
+
+    If `default` is not specified or None, empty dictionary is used for default.
+
+    Example:
+
+        "XBLOCK_SETTINGS": {
+            "my_block": {
+                "setting1": 1,
+                "setting2": []
+            },
+            "my_other_block": [1, 2, 3],
+            "MyThirdBlock": "QWERTY"
+        }
+
+        class MyBlock:      block_settings_key='my_block'
+        class MyOtherBlock: block_settings_key='my_other_block'
+        class MyThirdBlock: pass
+        class MissingBlock: pass
+
+        service = SettingsService()
+        service.get_settings_bucket(MyBlock())                      # { "setting1": 1, "setting2": [] }
+        service.get_settings_bucket(MyOtherBlock())                 # [1, 2, 3]
+        service.get_settings_bucket(MyThirdBlock())                 # "QWERTY"
+        service.get_settings_bucket(MissingBlock())                 # {}
+        service.get_settings_bucket(MissingBlock(), "default")      # "default"
+        service.get_settings_bucket(MissingBlock(), None)           # {}
+    """
+    xblock_settings_bucket_selector = 'block_settings_key'
+
+    def get_settings_bucket(self, block, default=None):
+        """ Gets xblock settings dictionary from settings. """
+        if not block:
+            raise ValueError("Expected XBlock instance, got {0} of type {1}".format(block, type(block)))
+
+        actual_default = default if default is not None else {}
+        xblock_settings_bucket = getattr(block, self.xblock_settings_bucket_selector, block.unmixed_class.__name__)
+        xblock_settings = settings.XBLOCK_SETTINGS if hasattr(settings, "XBLOCK_SETTINGS") else {}
+        return xblock_settings.get(xblock_settings_bucket, actual_default)

common/lib/xmodule/xmodule/tests/test_services.py

+"""
+Tests for SettingsService
+"""
+
+import ddt
+import mock
+from unittest import TestCase
+
+from django.conf import settings
+from django.test.utils import override_settings
+
+from xblock.runtime import Mixologist
+from xmodule.services import SettingsService
+
+
+class _DummyBlock(object):
+    """ Dummy Xblock class """
+    pass
+
+
+@ddt.ddt
+class TestSettingsService(TestCase):
+    """ Test SettingsService """
+
+    xblock_setting_key1 = 'dummy_block'
+    xblock_setting_key2 = 'other_dummy_block'
+
+    def setUp(self):
+        """ Setting up tests """
+        super(TestSettingsService, self).setUp()
+        self.settings_service = SettingsService()
+        self.xblock_mock = mock.Mock()
+        self.xblock_mock.block_settings_key = self.xblock_setting_key1
+        self.xblock_mock.unmixed_class = mock.Mock()
+        self.xblock_mock.unmixed_class.__name__ = self.xblock_setting_key2
+
+    def test_get_given_none_throws_value_error(self):
+        """  Test that given None throws value error """
+        with self.assertRaises(ValueError):
+            self.settings_service.get_settings_bucket(None)
+
+    def test_get_return_default_if_xblock_settings_is_missing(self):
+        """ Test that returns default (or None if default not set) if XBLOCK_SETTINGS is not set """
+        self.assertFalse(hasattr(settings, 'XBLOCK_SETTINGS'))  # precondition check
+        self.assertEqual(self.settings_service.get_settings_bucket(self.xblock_mock, 'zzz'), 'zzz')
+
+    def test_get_return_empty_dictionary_if_xblock_settings_and_default_is_missing(self):
+        """ Test that returns default (or None if default not set) if XBLOCK_SETTINGS is not set """
+        self.assertFalse(hasattr(settings, 'XBLOCK_SETTINGS'))  # precondition check
+        self.assertEqual(self.settings_service.get_settings_bucket(self.xblock_mock), {})
+
+    @override_settings(XBLOCK_SETTINGS={xblock_setting_key2: {'b': 1}})
+    def test_get_returns_none_or_default_if_bucket_not_found(self):
+        """ Test if settings service returns default if setting not found """
+        self.assertEqual(getattr(settings, 'XBLOCK_SETTINGS'), {self.xblock_setting_key2: {'b': 1}})
+        self.assertEqual(self.settings_service.get_settings_bucket(self.xblock_mock), {})
+        self.assertEqual(self.settings_service.get_settings_bucket(self.xblock_mock, 123), 123)
+
+    @override_settings(XBLOCK_SETTINGS={xblock_setting_key1: 42})
+    def test_get_returns_correct_value(self):
+        """ Test if settings service returns correct bucket """
+        self.assertEqual(getattr(settings, 'XBLOCK_SETTINGS'), {self.xblock_setting_key1: 42})
+        self.assertEqual(self.settings_service.get_settings_bucket(self.xblock_mock), 42)
+
+    @override_settings(XBLOCK_SETTINGS={xblock_setting_key2: "I'm a setting"})
+    def test_get_respects_block_settings_key(self):
+        """ Test if settings service respects block_settings_key value """
+        self.assertEqual(getattr(settings, 'XBLOCK_SETTINGS'), {self.xblock_setting_key2: "I'm a setting"})
+        self.xblock_mock.block_settings_key = self.xblock_setting_key2
+        self.assertEqual(self.settings_service.get_settings_bucket(self.xblock_mock), "I'm a setting")
+
+    @override_settings(XBLOCK_SETTINGS={_DummyBlock.__name__: [1, 2, 3]})
+    def test_get_uses_class_name_if_block_settings_key_is_not_set(self):
+        """ Test if settings service uses class name if block_settings_key attribute does not exist """
+        mixologist = Mixologist([])
+        block = mixologist.mix(_DummyBlock)
+        self.assertEqual(getattr(settings, 'XBLOCK_SETTINGS'), {"_DummyBlock": [1, 2, 3]})
+        self.assertEqual(self.settings_service.get_settings_bucket(block), [1, 2, 3])

lms/djangoapps/lms_xblock/runtime.py

@@ -10,6 +10,7 @@ from django.conf import settings
 from lms.djangoapps.lms_xblock.models import XBlockAsidesConfig
 from openedx.core.djangoapps.user_api.api import course_tag as user_course_tag_api
 from xmodule.modulestore.django import modulestore
+from xmodule.services import SettingsService
 from xmodule.library_tools import LibraryToolsService
 from xmodule.x_module import ModuleSystem
 from xmodule.partitions.partitions_service import PartitionService
@@ -202,6 +203,7 @@ class LmsModuleSystem(LmsHandlerUrls, ModuleSystem):  # pylint: disable=abstract
         )
         services['library_tools'] = LibraryToolsService(modulestore())
         services['fs'] = xblock.reference.plugins.FSService()
+        services['settings'] = SettingsService()
         self.request_token = kwargs.pop('request_token', None)
         super(LmsModuleSystem, self).__init__(**kwargs)