[Refactor] Slash-n-Burn Problem BuiltIn XBlock

[irfanuddinahmad]

See parent epic: openedx/openedx-platform#37819

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Rollout Position

Step 8 of 8 — Largest and highest-risk block (~15K LOC). The Problem/CAPA block is deeply integrated with the grading system and instructor dashboard, and supports many problem types (multiple choice, code input, circuit schematic, MATLAB, image input). Leave this for last.

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Block Details

Toggle	USE_EXTRACTED_PROBLEM_BLOCK in openedx/envs/common.py
Shim class	_BuiltInProblemBlock in xmodule/capa_block.py
Entrypoint	problem = "xmodule.capa_block:ProblemBlock" in pyproject.toml

Note on stale annotation: The toggle annotation in openedx/envs/common.py still says toggle_default: False but the code has been set to True (via refactor: Enable Extracted Problem XBlock #38152). The PR for this block should update the annotation to toggle_default: True before removing the toggle entirely.

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Checklist

Pre-condition

• Review PRs merged into the built-in Problem XBlock code in edx-platform after the extraction work was done — port any bug fixes or improvements to xblocks-contrib if not already there.
• Confirm all problem types (multiple choice, code input, circuit schematic, MATLAB, image input) work correctly in xblocks-contrib.
• Confirm grading pipeline integration is unaffected.

Steps (single PR)

• Fix stale annotation — update # .. toggle_default: False → # .. toggle_default: True at openedx/envs/common.py before removing the toggle.
• Remove the toggle — delete USE_EXTRACTED_PROBLEM_BLOCK from openedx/envs/common.py and all usages.
• Remove the shim — delete _BuiltInProblemBlock class and the from xblocks_contrib.problem import ProblemBlock as _ExtractedProblemBlock import from xmodule/capa_block.py.
• Remove the entrypoint — delete problem = "xmodule.capa_block:ProblemBlock" from pyproject.toml.
• Remove remaining assets:
  • xmodule/capa_block.py (Python class, 2,481 LOC)
  • xmodule/js/src/capa/ (display.js, imageinput.js, schematic.js — 7,759 LOC)
  • xmodule/static/css-builtin-blocks/ProblemBlockDisplay.css (2,304 LOC)
  • xmodule/templates/problem/ (template files)
  • Webpack entries ProblemBlockDisplay / ProblemBlockEditor in webpack.builtinblocks.config.js
• Run smoke tests on the extracted Problem block covering all problem types and grading scenarios.

[irfanuddinahmad]

Implementation PR: openedx/openedx-platform#38751