Update

app/decorators/course_decorator.rb

@@ -143,14 +143,14 @@ def apprenticeship
   end
 
   def sorted_subjects
-    object.course_subjects.map{ _1.subject.subject_name }.join('<br>').html_safe
+    object.course_subjects.map { _1.subject.subject_name }.join('<br>').html_safe
   end
 
   def chosen_subjects
     return sorted_subjects if master_subject_nil?
 
     if main_subject_is_modern_languages?
-      format_name(modern_language_subjects.to_a.push(additional_subjects.sort_by { |x| [x.subject.type, x.subject.subject_name] }).flatten.uniq.unshift(main_subject))
+      format_name(modern_language_subjects.to_a.push(additional_subjects.sort_by { |x| [x.type, x.subject_name] }).flatten.uniq.unshift(main_subject))
     elsif !main_subject_is_modern_languages? && modern_languages_subjects.present?
       format_name(additional_subjects.push(modern_language_subjects.to_a).flatten.uniq.unshift(main_subject))
     else
@@ -489,14 +489,14 @@ def main_subject_is_modern_languages?
   end
 
   def main_subject
-    Subject.find(course.master_subject_id)
+    @main_subject ||= Subject.find(course.master_subject_id)
   end
 
   def additional_subjects
-    object.course_subjects.reject { |subject| subject.subject_id == main_subject.id }
+  object.course_subjects.reject { |subject| subject.subject_id == main_subject.id }.map(&:subject)
   end
 
   def format_name(subjects)
-    course_subjects.map { _1.subject.subject_name }.join('<br>').html_safe
+    subjects.map { _1.subject_name }.join('<br>').html_safe
   end
 end

app/models/course.rb

@@ -579,7 +579,7 @@ def publish_enrichment(current_user)
   end
 
   def is_modern_language_course?
-    course_subjects.any? { |s| s.subject == SecondarySubject.modern_languages }
+    course_subjects.any? { |cs| cs.subject == SecondarySubject.modern_languages }
   end
 
   def sites=(desired_sites)
@@ -808,10 +808,10 @@ def remove_carat_from_error_messages
   end
 
   def modern_language_subjects
-    if persisted?
+    if persisted? && course_subjects.all?(&:persisted?)
       subjects.where(type: 'ModernLanguagesSubject')
     else
-      course_subjects.select { _1.subject.type == 'ModernLanguagesSubject' }
+    course_subjects.select { |cs| cs.subject.type == 'ModernLanguagesSubject' }.map(&:subject)
     end
   end
 
@@ -820,11 +820,7 @@ def master_subject_nil?
   end
 
   def has_any_modern_language_subject_type?
-    if persisted?
-      subjects.any? { |subject| subject.type == 'ModernLanguagesSubject' }
-    else
-      course_subjects.any? { |subject| subject.subject.type == 'ModernLanguagesSubject' }
-    end
+    course_subjects.any? { |cs| cs.subject.type == 'ModernLanguagesSubject' }
   end
 
   def current_published_enrichment
@@ -1011,11 +1007,7 @@ def has_the_modern_languages_secondary_subject_type?
     raise 'SecondarySubject not found' if SecondarySubject.nil?
     raise 'SecondarySubject.modern_languages not found' if SecondarySubject.modern_languages.nil?
 
-    if persisted?
-      subjects.any? { |subject| subject&.id == SecondarySubject.modern_languages.id }
-    else
-      course_subjects.any? { |subject| subject.subject&.id == SecondarySubject.modern_languages.id }
-    end
+    course_subjects.any? { |cs| cs.subject&.id == SecondarySubject.modern_languages.id }
   end
 
   def validate_has_languages
@@ -1030,9 +1022,9 @@ def validate_subject_count
 
     case level
     when 'primary', 'further_education'
-      errors.add(:subjects, 'has too many subjects') if subjects.count > 1
+      errors.add(:subjects, 'has too many subjects') if course_subjects.count > 1
     when 'secondary'
-      errors.add(:subjects, 'has too many subjects') if subjects.count > 2 && !has_any_modern_language_subject_type?
+      errors.add(:subjects, 'has too many subjects') if course_subjects.count > 2 && !has_any_modern_language_subject_type?
     end
   end
 

app/services/courses/assign_subjects_service.rb

@@ -54,14 +54,13 @@ def update_subjects
         if course.persisted?
           Course.transaction do
             course.course_subjects.clear
-            # subject_ids.each_with_index { |subject_id, position| puts subject_id, position}
             subject_ids.each_with_index do |subject_id, position|
               course.course_subjects.create(subject_id:, position:)
             end
             course.save
           end
         else
-          subject_ids.each_with_index do |subject_id|
+          subject_ids.each do |subject_id|
             course.course_subjects.build(subject_id:)
           end
         end

spec/decorators/course_decorator_spec.rb

@@ -260,8 +260,7 @@
     context 'when modern languages only is chosen' do
       let(:french) { build_stubbed(:modern_languages_subject, :french) }
       let(:german) { build_stubbed(:modern_languages_subject, :german) }
-      let(:mod_lang) { build_stubbed(:secondary_subject, :modern_languages) }
-      let(:subjects) { [mod_lang, french, german] }
+      let(:subjects) { [french, german] }
       let(:course) do
         build_stubbed(
           :course,

spec/models/course_spec.rb

@@ -2693,11 +2693,11 @@
     end
 
     context 'when course has two subjects' do
-      # it 'set the subordinate subject id to the second subjects_id' do
-      #   subordinate_subject = find_or_create(:secondary_subject, :physics)
-      #   course.subjects << subordinate_subject
-      #   expect(course.reload).to have_attributes({ subordinate_subject_id: subordinate_subject.id })
-      # end
+      it 'set the subordinate subject id to the second subjects_id' do
+        subordinate_subject = find_or_create(:secondary_subject, :physics)
+        course.subjects << subordinate_subject
+        expect(course.reload).to have_attributes({ subordinate_subject_id: subordinate_subject.id })
+      end
     end
   end