refactor(assessment): de-stutter answer.submission.submission via Answer/SubmissionQuestion#attempt alias

The extension accessor chain read as answer.submission.submission because Answer#submission
returns the Attempt base (FK column is misleadingly submission_id). Add a reader-only #attempt
alias on Answer and SubmissionQuestion and rewrite the 8 chain sites to answer.attempt.submission.
Attempt#submission (the extension has_one) is unchanged. Behavior-preserving.

Also extract the identical submission= writer that coerces a Submission (extension) to its
Attempt (base) — shared verbatim by Answer, SubmissionQuestion, and QuestionBundleAssignment —
into the new Course::Assessment::CoercesSubmissionToAttempt concern. Behavior-preserving.

Author: LWS49

app/controllers/course/assessment/submission/answer/programming/annotations_controller.rb

@@ -66,7 +66,7 @@ def create_topic_subscription
 
     # Ensure all group managers get a notification when someone adds a programming annotation
     # to the answer.
-    answer_course_user = @answer.submission.submission.course_user
+    answer_course_user = @answer.attempt.submission.course_user
     answer_course_user.my_managers.each do |manager|
       @discussion_topic.ensure_subscribed_by(manager.user)
     end

app/controllers/course/assessment/submission_question/comments_controller.rb

@@ -34,7 +34,7 @@ def create_topic_subscription
     @discussion_topic.ensure_subscribed_by(@submission_question.submission.creator)
 
     # Ensure all group managers get a notification when someone comments on this submission question
-    submission_question_course_user = @submission_question.submission.submission.course_user
+    submission_question_course_user = @submission_question.attempt.submission.course_user
     submission_question_course_user.my_managers.each do |manager|
       @discussion_topic.ensure_subscribed_by(manager.user)
     end

app/jobs/course/assessment/answer/base_auto_grading_job.rb

@@ -46,7 +46,7 @@ def perform_tracked(answer, redirect_to_path = nil)
       # `answer.submission` is the Attempt base; EXP (awarder/awarded_at/points_awarded) lives on its
       # Submission extension. Recompute against the extension (nil for a preview attempt, which has no
       # EXP and must be skipped).
-      submission = answer.submission.submission
+      submission = answer.attempt.submission
       if submission && update_exp?(submission)
         Course::Assessment::Submission::CalculateExpService.update_exp(submission)
       end

app/models/concerns/course/assessment/coerces_submission_to_attempt.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+# Lets a caller assign a `Course::Assessment::Submission` (the extension) to a `submission`
+# association whose real target is the `Course::Assessment::Attempt` base. The `belongs_to` writer
+# strictly checks `record.is_a?(reflection.klass)`, so a `Submission` would otherwise raise
+# `ActiveRecord::AssociationTypeMismatch`. Coerce it to its `Attempt` so every caller works
+# unchanged. Shared verbatim by Answer, SubmissionQuestion, and QuestionBundleAssignment.
+module Course::Assessment::CoercesSubmissionToAttempt
+  extend ActiveSupport::Concern
+
+  def submission=(value)
+    value = value.attempt if value.is_a?(Course::Assessment::Submission)
+    super
+  end
+end

app/models/course/assessment/answer.rb

@@ -57,18 +57,15 @@ class Course::Assessment::Answer < ApplicationRecord
   # base record: `submission_id` identifies an Attempt row (the base), not a Submission row.
   belongs_to :submission, class_name: 'Course::Assessment::Attempt', inverse_of: :answers,
                           foreign_key: 'submission_id'
+  include Course::Assessment::CoercesSubmissionToAttempt
+
   belongs_to :question, class_name: 'Course::Assessment::Question', inverse_of: nil
 
-  # Coerce a `Course::Assessment::Submission` passed here into its `Attempt` (the association's real
-  # target). Several question helpers accept either a `Submission` or an `Attempt` as their
-  # "submission" argument and thread it straight into `Answer::<Type>.new(submission: ...)`; without
-  # this coercion, passing the `Submission` raises `ActiveRecord::AssociationTypeMismatch`, since
-  # `belongs_to`'s writer strictly checks `record.is_a?(reflection.klass)`. Coercing here keeps every
-  # caller working without a per-call-site change.
-  def submission=(value)
-    value = value.attempt if value.is_a?(Course::Assessment::Submission)
-    super
-  end
+  # `attempt` is the accurate name for what `:submission` returns — the Attempt base record. Prefer it in
+  # new code: `answer.attempt.submission` reads clearly where `answer.submission.submission` stuttered (the
+  # FK column is misleadingly named `submission_id`). Reader-only alias; the association stays `:submission`
+  # for existing call sites.
+  alias_method :attempt, :submission
   belongs_to :grader, class_name: 'User', inverse_of: nil, optional: true
   has_one :auto_grading, class_name: 'Course::Assessment::Answer::AutoGrading',
                          dependent: :destroy, inverse_of: :answer, autosave: true

app/models/course/assessment/answer/programming_ability.rb

@@ -13,7 +13,7 @@ def allow_create_programming_files
     can :create_programming_files, Course::Assessment::Answer::Programming do |programming_answer|
       multiple_file_submission?(programming_answer.question) &&
         creator?(programming_answer.submission) &&
-        can_update_submission?(programming_answer.submission.submission) &&
+        can_update_submission?(programming_answer.attempt.submission) &&
         current_answer?(programming_answer)
     end
   end
@@ -22,7 +22,7 @@ def allow_destroy_programming_files
     can :destroy_programming_file, Course::Assessment::Answer::Programming do |programming_answer|
       multiple_file_submission?(programming_answer.question) &&
         creator?(programming_answer.submission) &&
-        can_update_submission?(programming_answer.submission.submission) &&
+        can_update_submission?(programming_answer.attempt.submission) &&
         current_answer?(programming_answer)
     end
   end

app/models/course/assessment/question_bundle_assignment.rb

@@ -5,21 +5,13 @@ class Course::Assessment::QuestionBundleAssignment < ApplicationRecord
                           foreign_key: :assessment_id, inverse_of: :question_bundle_assignments
   belongs_to :submission, class_name: 'Course::Assessment::Attempt', optional: true,
                           foreign_key: :submission_id, inverse_of: :question_bundle_assignments
+  include Course::Assessment::CoercesSubmissionToAttempt
+
   belongs_to :question_bundle, class_name: 'Course::Assessment::QuestionBundle',
                                foreign_key: :bundle_id, inverse_of: :question_bundle_assignments
 
   validate :submission_belongs_to_assessment_and_user
 
-  # Coerce a `Course::Assessment::Submission` passed here into its `Attempt` (the association's
-  # real target post-repoint) — mirrors the same coercion on `Course::Assessment::Answer`/
-  # `Course::Assessment::SubmissionQuestion` (see `Answer#submission=` for the full rationale).
-  # `spec/controllers/course/assessment/submission/submissions_controller_spec.rb`'s
-  # `randomized_submission` fixture passes the `Submission` half directly.
-  def submission=(value)
-    value = value.attempt if value.is_a?(Course::Assessment::Submission)
-    super
-  end
-
   private
 
   def submission_belongs_to_assessment_and_user

app/models/course/assessment/submission.rb

@@ -225,7 +225,7 @@ def self.on_dependent_status_change(answer)
     # `answer.submission` resolves to an Attempt (the association name is `:submission`, its
     # `class_name` is Attempt). `last_graded_time` is a course-coupled column that lives only on the
     # real Submission, reached via the attempt's `has_one :submission`.
-    answer.submission.submission&.last_graded_time = Time.now
+    answer.attempt.submission&.last_graded_time = Time.now
   end
 
   # Returns an array of submission rows for the given students and assessments.

app/models/course/assessment/submission_question.rb

@@ -12,20 +12,15 @@ class Course::Assessment::SubmissionQuestion < ApplicationRecord
   # since the association name stays `submission`.
   belongs_to :submission, class_name: 'Course::Assessment::Attempt', foreign_key: 'submission_id',
                           inverse_of: :submission_questions
+  include Course::Assessment::CoercesSubmissionToAttempt
+
   belongs_to :question, class_name: 'Course::Assessment::Question',
                         inverse_of: :submission_questions
 
-  # Coerce a `Course::Assessment::Submission` passed here into its `Attempt` (the association's
-  # real target post-repoint) — mirrors the same coercion on `Course::Assessment::Answer` (see its
-  # comment for the full rationale). Both `spec/factories/course_assessment_submission_questions.rb`'s
-  # own default `submission { create(:submission, ...) }` and
-  # `spec/models/course/assessment/submission_spec.rb`'s own `create(:course_assessment_submission_question,
-  # submission: submission, ...)` pass the `Submission` half, which otherwise raises
-  # `ActiveRecord::AssociationTypeMismatch`.
-  def submission=(value)
-    value = value.attempt if value.is_a?(Course::Assessment::Submission)
-    super
-  end
+  # `attempt` is the accurate name for what `:submission` returns — the Attempt base record. Prefer it in
+  # new code (e.g. `@submission_question.attempt.submission`); the association stays `:submission` for
+  # existing call sites. Reader-only alias.
+  alias_method :attempt, :submission
 
   has_many :threads, class_name: 'Course::Assessment::LiveFeedback::Thread',
                      inverse_of: :submission_question, dependent: :destroy

app/services/course/assessment/answer/ai_generated_post_service.rb

@@ -80,7 +80,7 @@ def create_topic_subscription(discussion_topic)
     # Ensure the student who wrote the answer amd all group managers
     # gets notified when someone comments on his answer
     discussion_topic.ensure_subscribed_by(@answer.submission.creator)
-    answer_course_user = @answer.submission.submission.course_user
+    answer_course_user = @answer.attempt.submission.course_user
     answer_course_user.my_managers.each do |manager|
       discussion_topic.ensure_subscribed_by(manager.user)
     end