Add make_course_usage_key method to modulestore

Different modulestores create different usage_keys
for the root course block.  This commit introduces
a new method on the modulestore so each store type
can implement its own.

This is required by the new Course Blocks API since
it wants to derive a usage key from a client-supplied
course key.

common/lib/xmodule/xmodule/modulestore/__init__.py

@@ -907,6 +907,14 @@ class ModuleStoreRead(ModuleStoreAssetBase):
         pass
 
     @abstractmethod
+    def make_course_usage_key(self, course_key):
+        """
+        Return a valid :class:`~opaque_keys.edx.keys.UsageKey` for this modulestore
+        that matches the supplied course_key.
+        """
+        pass
+
+    @abstractmethod
     def get_courses(self, **kwargs):
         '''
         Returns a list containing the top level XModuleDescriptors of the courses

common/lib/xmodule/xmodule/modulestore/mixed.py

@@ -313,6 +313,15 @@ class MixedModuleStore(ModuleStoreDraftAndPublished, ModuleStoreWriteBase):
         # Otherwise, return the key created by the default store
         return self.default_modulestore.make_course_key(org, course, run)
 
+    def make_course_usage_key(self, course_key):
+        """
+        Return a valid :class:`~opaque_keys.edx.keys.UsageKey` for the modulestore
+        that matches the supplied course_key.
+        """
+        assert isinstance(course_key, CourseKey)
+        store = self._get_modulestore_for_courselike(course_key)
+        return store.make_course_usage_key(course_key)
+
     @strip_key
     def get_course(self, course_key, depth=0, **kwargs):
         """

common/lib/xmodule/xmodule/modulestore/mongo/base.py

@@ -1033,6 +1033,13 @@ class MongoModuleStore(ModuleStoreDraftAndPublished, ModuleStoreWriteBase, Mongo
         """
         return CourseLocator(org, course, run, deprecated=True)
 
+    def make_course_usage_key(self, course_key):
+        """
+        Return a valid :class:`~opaque_keys.edx.keys.UsageKey` for this modulestore
+        that matches the supplied course_key.
+        """
+        return BlockUsageLocator(course_key, 'course', course_key.run)
+
     def get_course(self, course_key, depth=0, **kwargs):
         """
         Get the course with the given courseid (org/course/run)

common/lib/xmodule/xmodule/modulestore/split_mongo/split.py

@@ -70,6 +70,7 @@ from xmodule.errortracker import null_error_tracker
 from opaque_keys.edx.locator import (
     BlockUsageLocator, DefinitionLocator, CourseLocator, LibraryLocator, VersionTree, LocalId,
 )
+from ccx_keys.locator import CCXLocator, CCXBlockUsageLocator
 from xmodule.modulestore.exceptions import InsufficientSpecificationError, VersionConflictError, DuplicateItemError, \
     DuplicateCourseError
 from xmodule.modulestore import (
@@ -949,6 +950,14 @@ class SplitMongoModuleStore(SplitBulkWriteMixin, ModuleStoreWriteBase):
         """
         return CourseLocator(org, course, run)
 
+    def make_course_usage_key(self, course_key):
+        """
+        Return a valid :class:`~opaque_keys.edx.keys.UsageKey` for this modulestore
+        that matches the supplied course_key.
+        """
+        locator_cls = CCXBlockUsageLocator if isinstance(course_key, CCXLocator) else BlockUsageLocator
+        return locator_cls(course_key, 'course', 'course')
+
     def _get_structure(self, structure_id, depth, head_validation=True, **kwargs):
         """
         Gets Course or Library by locator

common/lib/xmodule/xmodule/modulestore/tests/test_mongo.py

@@ -758,6 +758,13 @@ class TestMongoModuleStore(TestMongoModuleStoreBase):
         # Clean up the data so we don't break other tests which apparently expect a particular state
         self.draft_store.delete_course(course.id, self.dummy_user)
 
+    def test_make_course_usage_key(self):
+        """Test that we get back the appropriate usage key for the root of a course key."""
+        course_key = CourseLocator(org="edX", course="101", run="2015")
+        root_block_key = self.draft_store.make_course_usage_key(course_key)
+        self.assertEqual(root_block_key.block_type, "course")
+        self.assertEqual(root_block_key.name, "2015")
+
 
 class TestMongoModuleStoreWithNoAssetCollection(TestMongoModuleStore):
     '''

common/lib/xmodule/xmodule/modulestore/tests/test_split_modulestore.py

@@ -10,6 +10,7 @@ import re
 import unittest
 import uuid
 
+import ddt
 from contracts import contract
 from nose.plugins.attrib import attr
 from django.core.cache import get_cache, InvalidCacheBackendError
@@ -23,7 +24,8 @@ from xmodule.modulestore.exceptions import (
     DuplicateItemError, DuplicateCourseError,
     InsufficientSpecificationError
 )
-from opaque_keys.edx.locator import CourseLocator, BlockUsageLocator, VersionTree, LocalId
+from opaque_keys.edx.locator import CourseKey, CourseLocator, BlockUsageLocator, VersionTree, LocalId
+from ccx_keys.locator import CCXBlockUsageLocator
 from xmodule.modulestore.inheritance import InheritanceMixin
 from xmodule.x_module import XModuleMixin
 from xmodule.fields import Date, Timedelta
@@ -596,6 +598,7 @@ class TestHasChildrenAtDepth(SplitModuleTest):
         self.assertFalse(ch3.has_children_at_depth(1))
 
 
+@ddt.ddt
 class SplitModuleCourseTests(SplitModuleTest):
     '''
     Course CRUD operation tests
@@ -908,6 +911,22 @@ class SplitModuleCourseTests(SplitModuleTest):
         version_history = modulestore().get_block_generations(second_problem.location)
         self.assertNotEqual(version_history.locator.version_guid, first_problem.location.version_guid)
 
+    @ddt.data(
+        ("course-v1:edx+test_course+test_run", BlockUsageLocator),
+        ("ccx-v1:edX+test_course+test_run+ccx@1", CCXBlockUsageLocator),
+    )
+    @ddt.unpack
+    def test_make_course_usage_key(self, course_id, root_block_cls):
+        """Test that we get back the appropriate usage key for the root of a course key.
+
+        In particular, we want to make sure that it properly handles CCX courses.
+        """
+        course_key = CourseKey.from_string(course_id)
+        root_block_key = modulestore().make_course_usage_key(course_key)
+        self.assertIsInstance(root_block_key, root_block_cls)
+        self.assertEqual(root_block_key.block_type, "course")
+        self.assertEqual(root_block_key.name, "course")
+
 
 class TestCourseStructureCache(SplitModuleTest):
     """Tests for the CourseStructureCache"""

common/lib/xmodule/xmodule/modulestore/xml.py

@@ -27,7 +27,7 @@ from xmodule.modulestore.xml_exporter import DEFAULT_CONTENT_FIELDS
 from xmodule.modulestore import ModuleStoreEnum, ModuleStoreReadBase, LIBRARY_ROOT, COURSE_ROOT
 from xmodule.tabs import CourseTabList
 from opaque_keys.edx.locations import SlashSeparatedCourseKey, Location
-from opaque_keys.edx.locator import CourseLocator, LibraryLocator
+from opaque_keys.edx.locator import CourseLocator, LibraryLocator, BlockUsageLocator
 
 from xblock.field_data import DictFieldData
 from xblock.runtime import DictKeyValueStore
@@ -821,6 +821,13 @@ class XMLModuleStore(ModuleStoreReadBase):
         """
         return CourseLocator(org, course, run, deprecated=True)
 
+    def make_course_usage_key(self, course_key):
+        """
+        Return a valid :class:`~opaque_keys.edx.keys.UsageKey` for this modulestore
+        that matches the supplied course_key.
+        """
+        return BlockUsageLocator(course_key, 'course', course_key.run)
+
     def get_courses(self, **kwargs):
         """
         Returns a list of course descriptors.  If there were errors on loading,