fix: lgeacy library block child.save fails in production instance while migrating

[navinkarkera]

Description

The child.save() call while migrating legacy library block to library version 2 fails with InvalidScopeError due to presence of LmsFieldData in _bound_field_data field.
Removing this call does not seem to have any adverse affect.

Error log:

Traceback (most recent call last):
  File "/openedx/edx-platform/cms/djangoapps/contentstore/views/preview.py", line 77, in preview_handler
    resp = instance.handle(handler, req, suffix)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/xblock/core.py", line 483, in handle
    return self.runtime.handle(self, handler_name, request, suffix)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/edx-platform/xmodule/x_module.py", line 1008, in handle
    return super().handle(block, handler_name, request, suffix=suffix)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/xblock/runtime.py", line 1057, in handle
    results = handler(request, suffix)
              ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/edx-platform/xmodule/library_content_block.py", line 401, in upgrade_to_v2_library
    self._v2_update_children_upstream_version()
  File "/openedx/edx-platform/xmodule/library_content_block.py", line 329, in _v2_update_children_upstream_version
    child.save()
  File "/openedx/venv/lib/python3.11/site-packages/xblock/core.py", line 514, in save
    self.force_save_fields(fields_to_save)
  File "/openedx/venv/lib/python3.11/site-packages/xblock/core.py", line 531, in force_save_fields
    self._field_data.set_many(self, fields_to_save_json)
  File "/openedx/venv/lib/python3.11/site-packages/xblock/field_data.py", line 166, in set_many
    field_data.set_many(block, new_update_dict)
  File "/openedx/venv/lib/python3.11/site-packages/xblock/field_data.py", line 88, in set_many
    self.set(block, key, value)
  File "/openedx/venv/lib/python3.11/site-packages/xblock/field_data.py", line 196, in set
    raise InvalidScopeError(f"{block}.{name} is read-only, cannot set")
xblock.exceptions.InvalidScopeError

Child field data:

{'_asides': [], '_cds_init_args': False, '_parent_block': <LegacyLibraryContentBlockWithMixins @5303 copied_from_block=None, downstream_customized=[], top_level_downstream_parent_key=None, upstream=None, upstream_display_name=None, upstream_version=None, upstream_version_declined=None, name=None, parent=BlockUsageLocator(CourseLocator('SampleTaxonomyOrg1', 'Chris456', 'chris456', None, None), 'vertical', 'd6b6fc5fd9104961aa83406773ddeea9'), tags=[], display_name='Randomized Content Block', course_edit_method='Studio', days_early_for_beta=None, due=None, edxnotes=False, edxnotes_visibility=True, giturl=None, graceperiod=None, graded=False, group_access={}, hide_from_toc=False, in_entrance_exam=False, matlab_api_key=None, max_attempts=None, relative_weeks_due=None, rerandomize='never', self_paced=False, show_correctness='always', show_reset_button=False, showanswer='finished', start=datetime.datetime(2030, 1, 1, 0, 0, tzinfo=tzlocal()), static_asset_path='', use_latex_compiler=False, user_partitions=[], video_auto_advance=False, video_bumper={}, video_speed_optimizations=True, visible_to_staff_only=False, xqa_key=None, chrome=None, default_tab=None, format=None, source_file=None, allow_resetting_children=False, children=[BlockUsageLocator(CourseLocator('SampleTaxonomyOrg1', 'Chris456', 'chris456', None, None), 'video', '4efeb593d14c61314395')], max_count=1, selected=[], xml_attributes={}, capa_type='any', is_migrated_to_v2=False, source_library_id='library-v1:tlmigration+tl123', source_library_version='68dc402f7ef716eebf702cf0'>, '_parent_block_id': BlockUsageLocator(CourseLocator('SampleTaxonomyOrg1', 'Chris456', 'chris456', None, None), 'library_content', '69629111a73b4504a0467511696a42ef'), '_child_cache': {}, '_runtime': <xmodule.modulestore.split_mongo.runtime.SplitModuleStoreRuntime object at 0x7f69e3bc34d0>, '_deprecated_per_instance_field_data': None, '_field_data_cache': {'upstream': 'lb:OpenCraft:chrislibrary:video:2cd6ffa4549b40ea8eb0521f9d34c3a8', 'upstream_version': 0}, '_dirty_fields': {<String upstream>: fields.EXPLICITLY_SET, <Integer upstream_version>: fields.EXPLICITLY_SET}, 'scope_ids': ScopeIds(user_id=40, block_type='video', def_id=ObjectId('68dc402f7ef716eebf702cef'), usage_id=BlockUsageLocator(CourseLocator('SampleTaxonomyOrg1', 'Chris456', 'chris456', None, None), 'video', '4efeb593d14c61314395')), '_edited_by': 40, '_edited_on': datetime.datetime(2025, 10, 30, 5, 51, 54, 319000, tzinfo=<bson.tz_util.FixedOffset object at 0x7f69e3bcdc50>), 'previous_version': None, 'update_version': ObjectId('6902fcfab505035c80dbd175'), 'source_version': None, 'definition_locator': DefinitionLocator(ObjectId('68dc402f7ef716eebf702cef'), 'video'), 'course_version': ObjectId('6902fcfab505035c80dbd175'), '_bound_field_data': LmsFieldData(ReadOnlyFieldData(InheritingFieldData(<xmodule.modulestore.split_mongo.split_mongo_kvs.SplitMongoKVS object at 0x7f69e3c2f010>)), KvsFieldData(<cms.djangoapps.contentstore.views.session_kv_store.SessionKeyValueStore object at 0x7f69e3c2c390>))}

Supporting information

• Related PR: feat: follow migrated legacy library content block #37405

Deadline

Before ULMO Cut off

Other information

Include anything else that will help reviewers and consumers understand the change.

• Does this change depend on other changes elsewhere?
• Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility.
• If your database migration can't be rolled back easily.

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[navinkarkera]

@kdmccormick @bradenmacdonald We noticed this issue in the sandbox. I am not sure if save() is even required as we are calling store.update_item to save the changes.

cc: @ChrisChV

[kdmccormick]

I haven't tested, but I'll take your word that you've tested that this still properly updates the upstream_version of the source block.

You weren't accidentally triggering this code from the LMS, were you? I'm not sure why you would be, but that's the only logical reason I could think of for .save() to cause this exception (of course, given how messy xblock field data APIs are, there are plenty of illogical reasons for .save() to cause this exception...)

[kdmccormick]

Suggested change

	# Save fails with InvalidScopeError due to `_bound_field_data` field containing LmsFieldData which
	# is ready-only. This was only seen in production instance and not observed in local dev instance.
	# child.save()
	# Save fails with InvalidScopeError due to `_bound_field_data` field containing LmsFieldData which
	# is ready-only. This was only seen in production instance and not observed in local dev instance.
	# child.save()

Unless you hope to reinstate child.save(), there's no reason to leave a comment on dead code. Just remove it :)

[navinkarkera]

Yeah, makes sense.

[navinkarkera]

You weren't accidentally triggering this code from the LMS, were you?

Nope, there is no option to trigger it in lms. It is really weird.

[navinkarkera]

Yeah, makes sense.