Allow instructors to also be CAs

app/assets/javascripts/course_user_data_edit.js

@@ -16,30 +16,27 @@ function formvalidation(form){
   }
 }
 
-// User can be at most one of the following: instructor, course assistant, or dropped (student)
 const $instructor_checkbox = $('#course_user_datum_instructor');
 const $course_assistant_checkbox = $('#course_user_datum_course_assistant');
 const $dropped_checkbox = $('#course_user_datum_dropped');
-const mutually_exclusive_fields = [
-  $instructor_checkbox, $course_assistant_checkbox, $dropped_checkbox
-];
+const $fields = [$instructor_checkbox, $course_assistant_checkbox, $dropped_checkbox];
 
-function mutual_exclusion() {
-  const fields = mutually_exclusive_fields; // For brevity
-  // Enable all fields
-  fields.forEach((field) => field.prop('disabled', false));
+function disable_fields(cur_field, excluded_fields) {
+  const checked = cur_field.is(':checked');
+  if (checked) {
+    excluded_fields.forEach((field) => {
+      field.prop('disabled', true);
+      field.prop('checked', false);
+    });
+  }
+}
 
-  // If any field is checked, disable the rest
-  fields.forEach((field, idx) => {
-    if (field.is(':checked')) {
-      fields.forEach((field2, idx2) => {
-        if (idx !== idx2) {
-          field2.prop('disabled', true);
-          field2.prop('checked', false);
-        }
-      });
-    }
-  });
+// User can't be dropped if they are an instructor or course assistant
+function instructor_or_ca_not_dropped() {
+  $fields.forEach((field) => field.prop('disabled', false));
+  disable_fields($instructor_checkbox, [$dropped_checkbox]);
+  disable_fields($course_assistant_checkbox, [$dropped_checkbox]);
+  disable_fields($dropped_checkbox, [$instructor_checkbox, $course_assistant_checkbox]);
 }
 
 $(document).ready(function(){
@@ -48,6 +45,6 @@ $(document).ready(function(){
     e.preventDefault();
   });
 
-  mutual_exclusion();
-  mutually_exclusive_fields.forEach((field) => field.on("click", mutual_exclusion));
+  instructor_or_ca_not_dropped();
+  $fields.forEach((field) => field.on("click", instructor_or_ca_not_dropped));
 });

app/models/course_user_datum.rb

@@ -31,7 +31,7 @@ def initialize(user_message, dev_message)
   accepts_nested_attributes_for :tweak, allow_destroy: true
   accepts_nested_attributes_for :user, allow_destroy: false
   validate :valid_nickname?
-  validate :instructor_or_ca_or_dropped
+  validate :instructor_or_ca_not_dropped
   after_create :create_AUDs_modulo_callbacks
 
   def self.conditions_by_like(value, *columns)
@@ -75,13 +75,11 @@ def valid_nickname?
     errors.add("nickname", "can only contain ASCII characters")
   end
 
-  # User can be at most one of the following: instructor, course assistant, or dropped (student)
-  def instructor_or_ca_or_dropped
-    status_count = [instructor?, course_assistant?, dropped?].count(true)
+  # User can't be dropped if they are an instructor or course assistant
+  def instructor_or_ca_not_dropped
+    return unless dropped? && (instructor? || course_assistant?)
 
-    return if status_count <= 1
-
-    errors.add(:base, "User can be at most one of instructor, course assistant, or dropped")
+    errors.add(:base, "User can't be dropped if they are an instructor or course assistant")
   end
 
   ##