Merge pull request #9862 from edx/aj/plat833-orphan-problem-with-preview-button

Orphans in split breaks preview button in Studio

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

@@ -1121,6 +1121,23 @@ class SplitMongoModuleStore(SplitBulkWriteMixin, ModuleStoreWriteBase):
         else:
             return []
 
+    def has_path_to_root(self, block_key, course):
+        """
+        Check recursively if an xblock has a path to the course root
+
+        :param block_key: BlockKey of the component whose path is to be checked
+        :param course: actual db json of course from structures
+
+        :return Bool: whether or not component has path to the root
+        """
+
+        xblock_parents = self._get_parents_from_structure(block_key, course.structure)
+        if len(xblock_parents) == 0 and block_key.type in ["course", "library"]:
+            # Found, xblock has the path to the root
+            return True
+
+        return any(self.has_path_to_root(xblock_parent, course) for xblock_parent in xblock_parents)
+
     def get_parent_location(self, locator, **kwargs):
         """
         Return the location (Locators w/ block_ids) for the parent of this location in this
@@ -1134,9 +1151,19 @@ class SplitMongoModuleStore(SplitBulkWriteMixin, ModuleStoreWriteBase):
             raise ItemNotFoundError(locator)
 
         course = self._lookup_course(locator.course_key)
-        parent_ids = self._get_parents_from_structure(BlockKey.from_usage_key(locator), course.structure)
+        all_parent_ids = self._get_parents_from_structure(BlockKey.from_usage_key(locator), course.structure)
+
+        # Check and verify the found parent_ids are not orphans; Remove parent which has no valid path
+        # to the course root
+        parent_ids = [
+            valid_parent
+            for valid_parent in all_parent_ids
+            if self.has_path_to_root(valid_parent, course)
+        ]
+
         if len(parent_ids) == 0:
             return None
+
         # find alphabetically least
         parent_ids.sort(key=lambda parent: (parent.type, parent.id))
         return BlockUsageLocator.make_relative(

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

@@ -643,7 +643,7 @@ class TestMixedModuleStore(CommonMixedModuleStoreSetup):
         test_course = self.store.create_course('test_org', 'test_course', 'test_run', self.user_id)
 
         # create sequential and vertical to test against
-        sequential = self.store.create_item(self.user_id, test_course.id, 'sequential', 'test_sequential')
+        sequential = self.store.create_child(self.user_id, test_course.location, 'sequential', 'test_sequential')
         vertical = self.store.create_child(self.user_id, sequential.location, 'vertical', 'test_vertical')
 
         # publish sequential changes