move deleted enrollments when cross listing sections

fixes CNVS-13828

test plan
 - prior to checking out patch set
 - enroll a user in a section
 - delete the enrollment
 - cross list the section
 - attempt to add user to sections new course
 - it should fail
 - checkout patch set and run migration
 - attempt to add user to sections new course
 - it should succeed

 - enroll a user in a section
 - delete the enrollment
 - cross list the section
 - attempt to add user to sections new course
 - it should work (it will restore the old enrollment)

 - enroll a user in a cross listed section
 - delete the enrollment
 - uncross list the section
 - attempt to add the user to the sections current course
 - it should work (it will restore the old enrollment)

Change-Id: Ib397f96b0761d87bf6f9fb11ffc978012f0f5b39
Reviewed-on: https://gerrit.instructure.com/37036
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jeremy Putnam <jeremyp@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>

app/models/course_section.rb

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2011 - 2013 Instructure, Inc.
+# Copyright (C) 2011 - 2014 Instructure, Inc.
 #
 # This file is part of Canvas.
 #
@@ -180,15 +180,15 @@ class CourseSection < ActiveRecord::Base
     old_course.course_sections.reset
     course.course_sections.reset
     assignment_overrides.active.destroy_all
-    user_ids = self.enrollments.map(&:user_id).uniq
+    user_ids = self.all_enrollments.map(&:user_id).uniq
 
     old_course_is_unrelated = old_course.id != self.course_id && old_course.id != self.nonxlist_course_id
     if self.root_account_id_changed?
       self.save!
-      self.enrollments.update_all :course_id => course, :root_account_id => self.root_account_id
+      self.all_enrollments.update_all :course_id => course, :root_account_id => self.root_account_id
     else
       self.save!
-      self.enrollments.update_all :course_id => course
+      self.all_enrollments.update_all :course_id => course
     end
     User.send_later_if_production(:update_account_associations, user_ids) if old_course.account_id != course.account_id && !User.skip_updating_account_associations?
     if old_course.id != self.course_id && old_course.id != self.nonxlist_course_id

db/migrate/20140628015850_fix_invalid_course_ids_for_enrollments.rb

@@ -0,0 +1,11 @@
+class FixInvalidCourseIdsForEnrollments < ActiveRecord::Migration
+  tag :postdeploy
+  disable_ddl_transaction!
+
+  def self.up
+    DataFixup::FixInvalidCourseIdsOnEnrollments.send_later_if_production(:run)
+  end
+
+  def self.down
+  end
+end

lib/data_fixup/fix_invalid_course_ids_on_enrollments.rb

@@ -0,0 +1,9 @@
+module DataFixup::FixInvalidCourseIdsOnEnrollments
+  def self.run
+    Enrollment.joins(:course_section).
+      where("course_sections.course_id<>enrollments.course_id").
+      includes(:course_section).find_each do |e|
+      Enrollment.where(id: e).update_all(course_id: e.course_section.course_id)
+    end
+  end
+end

spec/models/course_section_spec.rb

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2011 - 2013 Instructure, Inc.
+# Copyright (C) 2011 - 2014 Instructure, Inc.
 #
 # This file is part of Canvas.
 #
@@ -159,6 +159,8 @@ describe CourseSection, "moving to new course" do
     e = course1.enroll_user(u, 'StudentEnrollment', :section => cs)
     e.workflow_state = 'active'
     e.save!
+    #should also move deleted enrollments
+    e.destroy
     course1.reload
     course2.reload
     course3.workflow_state = 'active'