In content library transformer handle the cases where the old selected modules…

In content library transformer handle the cases where the old selected modules are no longer valid and update the user's set of selected modules.

common/lib/xmodule/xmodule/library_content_module.py

@@ -135,84 +135,116 @@ class LibraryContentModule(LibraryContentFields, XModule, StudioEditableModule):
     any particular student.
     """
 
-    def _publish_event(self, event_name, result, **kwargs):
-        """ Helper method to publish an event for analytics purposes """
-        event_data = {
-            "location": unicode(self.location),
-            "result": result,
-            "previous_count": getattr(self, "_last_event_result_count", len(self.selected)),
-            "max_count": self.max_count,
-        }
-        event_data.update(kwargs)
-        self.runtime.publish(self, "edx.librarycontentblock.content.{}".format(event_name), event_data)
-        self._last_event_result_count = len(result)  # pylint: disable=attribute-defined-outside-init
-
-    def selected_children(self):
+    @classmethod
+    def make_selection(cls, selected, children, max_count, mode, location, lib_tools, emit):
         """
-        Returns a set() of block_ids indicating which of the possible children
-        have been selected to display to the current user.
+        Dynamically selects block_ids indicating which of the possible children are displayed to the current user.
 
-        This reads and updates the "selected" field, which has user_state scope.
+        Arguments:
+            selected - list of (block_type, block_id) tuples assigned to this student
+            children - children of this block
+            max_count - number of components to display to each student
+            mode - how content is drawn from the library
+            location -
+            lib_tools - instance of LibraryToolsService
+            emit - function to emit events
 
-        Note: self.selected and the return value contain block_ids. To get
-        actual BlockUsageLocators, it is necessary to use self.children,
-        because the block_ids alone do not specify the block type.
+        Returns:
+            a set of (block_type, block_id) tuples used to record
+            which random/first set of matching blocks was selected per user
         """
-        if hasattr(self, "_selected_set"):
-            # Already done:
-            return self._selected_set  # pylint: disable=access-member-before-definition
 
-        selected = set(tuple(k) for k in self.selected)  # set of (block_type, block_id) tuples assigned to this student
+        def publish_event(event_name, result, **kwargs):
+            """ Helper method to publish an event for analytics purposes """
+            event_data = {
+                "location": unicode(location),
+                "result": result,
+                "previous_count": last_event_result_count,
+                "max_count": max_count,
+            }
+            event_data.update(kwargs)
+            emit("edx.librarycontentblock.content.{}".format(event_name), event_data)
 
-        lib_tools = self.runtime.service(self, 'library_tools')
-        format_block_keys = lambda keys: lib_tools.create_block_analytics_summary(self.location.course_key, keys)
+        last_event_result_count = len(selected)
+        selected = set(tuple(k) for k in selected)  # set of (block_type, block_id) tuples assigned to this student
+        format_block_keys = lambda keys: lib_tools.create_block_analytics_summary(location.course_key, keys)
 
         # Determine which of our children we will show:
-        valid_block_keys = set([(c.block_type, c.block_id) for c in self.children])  # pylint: disable=no-member
+        valid_block_keys = set([(c.block_type, c.block_id) for c in children])  # pylint: disable=no-member
         # Remove any selected blocks that are no longer valid:
         invalid_block_keys = (selected - valid_block_keys)
         if invalid_block_keys:
             selected -= invalid_block_keys
             # Publish an event for analytics purposes:
             # reason "invalid" means deleted from library or a different library is now being used.
-            self._publish_event(
+            publish_event(
                 "removed",
                 result=format_block_keys(selected),
                 removed=format_block_keys(invalid_block_keys),
                 reason="invalid"
             )
+
         # If max_count has been decreased, we may have to drop some previously selected blocks:
         overlimit_block_keys = set()
-        while len(selected) > self.max_count:
+        while len(selected) > max_count:
             overlimit_block_keys.add(selected.pop())
+
         if overlimit_block_keys:
             # Publish an event for analytics purposes:
-            self._publish_event(
+            publish_event(
                 "removed",
                 result=format_block_keys(selected),
                 removed=format_block_keys(overlimit_block_keys),
                 reason="overlimit"
             )
+
         # Do we have enough blocks now?
-        num_to_add = self.max_count - len(selected)
-        if num_to_add > 0:
+        num_to_add = max_count - len(selected)
+
         added_block_keys = None
+        if num_to_add > 0:
             # We need to select [more] blocks to display to this user:
             pool = valid_block_keys - selected
-            if self.mode == "random":
+            if mode == "random":
                 num_to_add = min(len(pool), num_to_add)
                 added_block_keys = set(random.sample(pool, num_to_add))
                 # We now have the correct n random children to show for this user.
             else:
                 raise NotImplementedError("Unsupported mode.")
             selected |= added_block_keys
+
             if added_block_keys:
                 # Publish an event for analytics purposes:
-                self._publish_event(
+                publish_event(
                     "assigned",
                     result=format_block_keys(selected),
                     added=format_block_keys(added_block_keys)
                 )
+
+        return selected
+
+    def selected_children(self):
+        """
+        Returns a set() of block_ids indicating which of the possible children
+        have been selected to display to the current user.
+
+        This reads and updates the "selected" field, which has user_state scope.
+
+        Note: self.selected and the return value contain block_ids. To get
+        actual BlockUsageLocators, it is necessary to use self.children,
+        because the block_ids alone do not specify the block type.
+        """
+        if hasattr(self, "_selected_set"):
+            # Already done:
+            return self._selected_set  # pylint: disable=access-member-before-definition
+
+        lib_tools = self.runtime.service(self, 'library_tools')
+        emit = lambda *args: self.runtime.publish(self, *args)
+
+        selected = self.make_selection(
+            self.selected, self.children, self.max_count, "random", self.location, lib_tools, emit
+        )
+
         # Save our selections to the user state, to ensure consistency:
         self.selected = list(selected)  # TODO: this doesn't save from the LMS "Progress" page.
         # Cache the results

lms/djangoapps/course_blocks/transformers/library_content.py

@@ -6,6 +6,10 @@ from courseware.access import _has_access_to_course
 from courseware.models import StudentModule
 from opaque_keys.edx.locator import BlockUsageLocator
 from openedx.core.lib.block_cache.transformer import BlockStructureTransformer
+from xmodule.library_content_module import LibraryContentModule
+from xmodule.library_tools import LibraryToolsService
+from xmodule.modulestore.django import modulestore
+from eventtracking import tracker
 
 
 class ContentLibraryTransformer(BlockStructureTransformer):
@@ -47,6 +51,9 @@ class ContentLibraryTransformer(BlockStructureTransformer):
         Returns:
             dict[UsageKey: dict]
         """
+        block_structure.request_xblock_fields('mode')
+        block_structure.request_xblock_fields('max_count')
+
         # For each block check if block is library_content.
         # If library_content add children array to content_library_children field
         for block_key in block_structure.topological_traversal():
@@ -63,6 +70,22 @@ class ContentLibraryTransformer(BlockStructureTransformer):
             user_info(object)
             block_structure (BlockStructureCollectedData)
         """
+        store = modulestore()
+        lib_tools = LibraryToolsService(store)
+
+        def build_key(block_type, block_id):
+            """
+            Helper method to build a BlockUsageLocator for user_info.course_key
+            """
+            return BlockUsageLocator(user_info.course_key, block_type, block_id)
+
+        def update_selection(selected, children, max_count, mode, location):
+            """
+            Helper method to update library content selection
+            """
+            return LibraryContentModule.make_selection(
+                selected, children, max_count, mode, location, lib_tools, tracker.emit
+            )
 
         def check_child_removal(block_key):
             """
@@ -82,19 +105,25 @@ class ContentLibraryTransformer(BlockStructureTransformer):
             library_children = block_structure.get_transformer_block_data(block_key, self, 'content_library_children')
             if library_children:
                 children.extend(library_children)
+                selected = []
+                mode = block_structure.get_xblock_field(block_key, 'mode')
+                max_count = block_structure.get_xblock_field(block_key, 'max_count')
+
                 # Retrieve "selected" json from LMS MySQL database.
                 modules = self._get_selected_modules(user_info.user, user_info.course_key, block_key)
                 for module in modules:
                     module_state = module.state
                     state_dict = json.loads(module_state)
                     # Check all selected entries for this user on selected library.
-                    # Add all selected to selected_children list.
+                    # Add all selected to selected list.
                     for state in state_dict['selected']:
-                        usage_key = BlockUsageLocator(
-                            user_info.course_key, block_type=state[0], block_id=state[1]
-                        )
+                        usage_key = build_key(state[0], state[1])
                         if usage_key in library_children:
-                            selected_children.append(usage_key)
+                            selected.append((state[0], state[1]))
+
+                # update selected
+                selected = update_selection(selected, children, max_count, mode, block_key)
+                selected_children.extend([build_key(s[0], s[1]) for s in selected])
 
         # Check and remove all non-selected children from course structure.
         block_structure.remove_block_if(

lms/djangoapps/course_blocks/transformers/tests/test_library_content.py

@@ -127,10 +127,15 @@ class ContentLibraryTransformerTestCase(CourseStructureTestCase):
             transformers={self.transformer}
         )
 
-        self.assertEqual(
-            set(trans_block_structure.get_block_keys()),
-            self.get_block_key_set(self.blocks, 'course', 'chapter1', 'lesson1', 'vertical1', 'library_content1')
-        )
+        # Should dynamically assign a block to student
+        trans_keys = set(trans_block_structure.get_block_keys())
+        block_key_set = self.get_block_key_set(self.blocks, 'course', 'chapter1', 'lesson1', 'vertical1', 'library_content1')
+        for key in block_key_set:
+            self.assertIn(key, trans_keys)
+
+        vertical2_selected = self.get_block_key_set(self.blocks, 'vertical2').pop() in trans_keys
+        vertical3_selected = self.get_block_key_set(self.blocks, 'vertical3').pop() in trans_keys
+        self.assertTrue(vertical2_selected or vertical3_selected)
 
         # Check course structure again, with mocked selected modules for a user.
         with mock.patch(