[DEPR]: Extraneous XBlock Mixins #714

Proposal Date

2024-01-31

Target Ticket Acceptance Date

2024-02-09

Earliest Open edX Named Release Without This Functionality

Redwood - 2024-04

Rationale

The implementations of the XBlock and XBlockAside classes are chopped into about a dozen tiny mixins. This was done many years ago, probably for some mix of reasons including code organization and theoretical reusability. Now, in 2024 in the openedx GitHub org, there are uses of the XBlock, XBlockAside, and XBlockMixin classes, but we do not see uses of any of the other classes or mixins (other than one extraneous reference to HandlersMixin in edx-platform, which can be removed).

Unfortunately, these mixins make it harder/impossible to write robust type constraints for XBlock and XBlockAside. They also make it harder to find code in the XBlock package. See discussion.

Removal

In an upcoming XBlock 2.0.0 release...

• Removed: class xblock.core.SharedBlockBase.
• Removed: module xblock.mixins, including...
  • these classes, collapsed into xblock.core.Blocklike:
    • xblock.mixins.RuntimeServicesMixin
    • xblock.mixins.ScopedStorageMixin
    • xblock.mixins.IndexInfoMixin
    • xblock.mixins.XmlSerializationMixin
    • xblock.mixins.HandlersMixin
  • these classes, collapsed into xblock.core.XBlock:
    • xblock.mixins.ChildrenModelMetaclass
    • xblock.mixins.HierarchyMixin
    • xblock.mixins.ViewsMixin
• New: class xblock.core.Blocklike, serving as a shared base for xblock.core.XBlockMixin, xblock.core.XBlock, and xblock.core.XBlockAsidse.
• No functional changes to xblock.plugin.Plugin, xblock.core.XBlock and xblock.core.XBlockAside.
• Backwards-compatible enhancements to xblock.core.XBlockMixin include the functionality of these former classes:
  • xblock.mixins.IndexInfoMixin
  • xblock.mixins.XmlSerializationMixin
  • xblock.mixins.HandlersMixin

The resulting class hierarchy will look like this:

# xblock/plugin.py:
class Plugin:
   ... # No changes.

# xblock/core.py:
class Blocklike:
   ... # Collapse in: RuntimeServicesMixin, ScopedStorageMixin, XmlSerializationMixin, HandlersMixin, IndexInfoMixin
class XBlockMixin(Blocklike):
   ... # No changes (but XmlSerializationMixin, HandlersMixin, and IndexInfoMixin have been added via Blocklike).
class XBlockAside(Blocklike, Plugin):
   ... # No changes.
class XBlock(Blocklike, Plugin):
   ... # Collapse in: HierarchyMixin, ViewMixin

Replacement

See "Removal"

Deprecation

No plan.

Migration

See "Removal"

Additional Info

No response

Task List

No response