Exclude dropped students from watchlist during refresh and updates

app/controllers/metrics_controller.rb

@@ -64,9 +64,9 @@ def get_watchlist_instances
     user_data = User.joins(:course_user_data)
                     .where(course_user_data: { id: course_user_data_ids })
                     .select('users.id as user_id,
-								     users.first_name,
-									 users.last_name,users.email,
-									 course_user_data.id as course_user_datum_id')
+								             users.first_name,
+									           users.last_name,users.email,
+									           course_user_data.id as course_user_datum_id')
                     .as_json
 
     user_hash = user_data.index_by do |entry|

app/models/watchlist_instance.rb

@@ -42,9 +42,13 @@ def self.refresh_instances_for_course(course_name, metrics_update = false)
       # no-op
     else
       # case 2: current risk conditions exist
+
+      # remove dropped students from watchlist
+      filtered_instances = remove_dropped_students(course, current_instances)
+
       # take category blocklist into consideration
       new_instances, deprecated_instances = add_new_instances_for_conditions(
-        current_conditions, course, category_blocklist, current_instances
+        current_conditions, course, category_blocklist, filtered_instances
       )
     end
 
@@ -342,14 +346,31 @@ def delete_watchlist_instance
   end
   # rubocop:enable Style/GuardClause
 
+  ##
+  # Archives instances of dropped students
+  #
+  # Given course and current instances
+  # archives instances where the student is no longer in the course
+  # returns the remaining instances
+  def self.remove_dropped_students(course, current_instances)
+    dropped_cuds = CourseUserDatum.where(course_id: course.id, instructor: false,
+                                         course_assistant: false, dropped: true).pluck(:id)
+    current_instances.where(course_user_datum_id: dropped_cuds)
+                     .find_each(&:archive_watchlist_instance)
+    current_instances.where.not(course_user_datum_id: dropped_cuds)
+  end
+
   def self.add_new_instances_for_conditions(conditions, course, category_blocklist,
                                             current_instances)
     new_instances = []
+
+    # prevent dropped students from being considered
     course_user_data = CourseUserDatum.where(course_id: course.id, instructor: false,
-                                             course_assistant: false)
+                                             course_assistant: false, dropped: false)
 
     # new
     criteria2 = current_instances.where(status: :pending)
+
     # contacted or resolved
     criteria1 = current_instances - criteria2
     deprecated_instances = current_instances

app/views/metrics/index.html.erb

@@ -102,7 +102,7 @@
               </div>
               <div class="results"></div>
             </div>
-          <h5> Archived students </h5> <b>Resolved and contacted students becomes archived when student metrics are changed </b>
+          <h5> Archived students </h5> <b>Resolved and contacted students become archived when student metrics are changed OR when dropped from the course </b>
         </div>
         <span class="instances" id="archived_instances"></span>
         </div>