Require pair programming for a given set of exercises

app/controllers/exercises_controller.rb

@@ -315,6 +315,8 @@ class ExercisesController < ApplicationController
       # we are just acting on behalf of a single user who has already worked on this exercise as part of a programming group **in the context of the current study group**
       session[:pg_id] = pg.id
       @current_contributor = pg
+    elsif session[:pg_id].blank? && PairProgramming23Study.participate_in_pp?(current_user, @exercise) && PairProgramming23Study::FORCED_EXERCISE_IDS.include?(@exercise.id)
+      return redirect_back(fallback_location: new_exercise_programming_group_path(@exercise))
     elsif session[:pg_id].blank? && PairProgramming23Study.participate?(current_user, @exercise) && current_user.submissions.where(study_group_id: current_user.current_study_group_id, exercise: @exercise).none?
       Event.find_or_create_by(category: 'pp_work_alone', user: current_user, exercise: @exercise, data: nil, file_id: nil)
       current_user.pair_programming_waiting_users&.find_by(exercise: @exercise)&.update(status: :worked_alone)

app/views/programming_groups/new.html.slim

@@ -30,9 +30,10 @@ h1.d-inline-block = t('programming_groups.new.create_programming_pair')
     .col-12.d-none.d-md-block
       = render('form')
 
-  .row
-    .col-12
-      h5 = t('programming_groups.new.work_alone')
-      == t('programming_groups.new.work_alone_description', path: implement_exercise_path(@exercise))
+  - unless PairProgramming23Study.participate_in_pp?(current_user, @exercise) && PairProgramming23Study::FORCED_EXERCISE_IDS.include?(@exercise.id)
+    .row
+      .col-12
+        h5 = t('programming_groups.new.work_alone')
+        == t('programming_groups.new.work_alone_description', path: implement_exercise_path(@exercise))
 
 = render('shared/modal', classes: 'modal-lg', id: 'modal-info-pair-programming', template: 'programming_groups/_info_pair_programming', title: t('programming_groups.new.pair_programming_info'))