Correctly check observer self-enrollments across shards

When loading dashboard cards for users who are observers but have
their own enrollments as well, we check if the selected observee has
the same ID as the current user when determining which enrollments to
load. This causes issues if some the logged-in users enrollments are
on a different shard from their home shard, since we were comparing a
passed-in global ID to the user's local ID in that scenario.

This PS updates the observed user's own-enrollments check to actually
load the associated user before comparisons, ensuring that Switchman
takes the cross-shard nature of this check into account.

fixes LS-2820, LS-2834
flag = k5_parent_support

Test plan:
  - Make sure you have muliple shards set up
  - Find a user with the following properties:
    * Is not observing any users
    * Is enrolled in some courses in a C4E account
    * Has logins on multiple trusted shards
  - Enroll a user as an observer in a concluded course on one shard
  - Log in as the user on a different shard
  - Expect the user's enrollments to show up as usual
  - To verify the behavior is correct, you can compare the results of
    these API calls (they should return the same results)
    * /api/v1/dashboard/dashboard_cards
    * /api/v1/dashboard/dashboard_cards?observed_user=<user's gid>

Change-Id: Ibbdf6cd0d80493198203c59a62b2e07464b13cf6
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/279002
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Jackson Howe <jackson.howe@instructure.com>
QA-Review: Jackson Howe <jackson.howe@instructure.com>
Product-Review: Jeff Largent <jeff.largent@instructure.com>

app/controllers/favorites_controller.rb

@@ -70,7 +70,7 @@ class FavoritesController < ApplicationController
   def list_favorite_courses
     includes = Set.new(Array(params[:include]))
     opts = {}
-    opts[:observee_user] = params[:observed_user].to_i if params.key?(:observed_user)
+    opts[:observee_user] = User.find_by(id: params[:observed_user].to_i) || @current_user if params.key?(:observed_user)
 
     courses = @current_user.menu_courses(nil, opts)
     if courses.any? && value_to_boolean(params[:exclude_blueprint_courses])

app/controllers/users_controller.rb

@@ -583,7 +583,7 @@ class UsersController < ApplicationController
 
   def dashboard_cards
     opts = {}
-    opts[:observee_user] = params[:observed_user].to_i if params.key?(:observed_user)
+    opts[:observee_user] = User.find_by(id: params[:observed_user].to_i) || @current_user if params.key?(:observed_user)
     dashboard_courses = map_courses_for_menu(@current_user.menu_courses(nil, opts), tabs: DASHBOARD_CARD_TABS)
     published, unpublished = dashboard_courses.partition { |course| course[:published] }
     Rails.cache.write(['last_known_dashboard_cards_published_count', @current_user.global_id].cache_key, published.count)

app/models/user.rb

@@ -425,12 +425,12 @@ class User < ActiveRecord::Base
   after_save :self_enroll_if_necessary
 
   def courses_for_enrollments(enrollment_scope, associated_user = nil)
-    if associated_user && associated_user != id
+    if associated_user && associated_user != self
       Course.active.joins(:observer_enrollments)
             .merge(enrollment_scope.except(:joins))
-            .where(enrollments: { associated_user_id: associated_user })
+            .where(enrollments: { associated_user_id: associated_user.id })
     else
-      enrollments_to_include = associated_user == id ? :non_observer_enrollments : :all_enrollments
+      enrollments_to_include = associated_user == self ? :non_observer_enrollments : :all_enrollments
       Course.active.joins(enrollments_to_include).merge(enrollment_scope.except(:joins)).distinct
     end
   end

spec/models/user_spec.rb

@@ -806,16 +806,16 @@ describe User do
         observer_enrollment2.save!
 
         @teacher_course = course_factory(:course_name => "English ", :active_course => true)
-        teacher_entollment = @teacher_course.enroll_user(@user, 'TeacherEnrollment', :enrollment_state => 'active')
-        teacher_entollment.save!
+        teacher_enrollment = @teacher_course.enroll_user(@user, 'TeacherEnrollment', :enrollment_state => 'active')
+        teacher_enrollment.save!
 
         @student_course = course_factory(:course_name => "Leadership", :active_course => true)
-        teacher_entollment = @student_course.enroll_user(@user, 'StudentEnrollment', :enrollment_state => 'active')
-        teacher_entollment.save!
+        student_enrollment = @student_course.enroll_user(@user, 'StudentEnrollment', :enrollment_state => 'active')
+        student_enrollment.save!
       end
 
       it "returns observed courses related to the associated_user" do
-        expect(@observer.courses_with_primary_enrollment(:current_and_invited_courses, nil, :observee_user => @student.id)
+        expect(@observer.courses_with_primary_enrollment(:current_and_invited_courses, nil, :observee_user => @student)
         .map { |c| [c.id, c.primary_enrollment_type] }).to eq [
           [@observer_course2.id, 'ObserverEnrollment'],
           [@observer_course.id, 'ObserverEnrollment']
@@ -824,12 +824,39 @@ describe User do
 
       it "returns only own courses if the associated_user is the current user" do
         expect(@observer
-        .courses_with_primary_enrollment(:current_and_invited_courses, nil, :observee_user => @observer.id)
+        .courses_with_primary_enrollment(:current_and_invited_courses, nil, :observee_user => @observer)
         .map { |c| [c.id, c.primary_enrollment_type] }).to eq [
           [@teacher_course.id, 'TeacherEnrollment'],
           [@student_course.id, 'StudentEnrollment']
         ]
       end
+
+      describe "with cross sharding" do
+        specs_require_sharding
+
+        before(:once) do
+          @shard2.activate do
+            account = Account.create!
+            course_with_teacher(account: account, active_all: true)
+
+            observer_enrollment = @observer_course.enroll_user(@teacher, 'ObserverEnrollment', :enrollment_state => 'active')
+            observer_enrollment.associated_user_id = @student.id
+            observer_enrollment.save!
+          end
+        end
+
+        it "returns the user's courses across shards when they are the observee" do
+          own_courses = @teacher.courses_with_primary_enrollment(:current_and_invited_courses, nil, :observee_user => @teacher)
+          expect(own_courses.count).to be 1
+          expect(own_courses.first.id).to be @course.id
+        end
+
+        it "returns the observer's courses across shards when observing someone else" do
+          observed_courses = @teacher.courses_with_primary_enrollment(:current_and_invited_courses, nil, :observee_user => @student)
+          expect(observed_courses.count).to be 1
+          expect(observed_courses.first.id).to be @observer_course.id
+        end
+      end
     end
 
     it "includes invitations to temporary users" do