Allow excluding users with no results

closes OUT-1859

test plan:
  - in a course, create about 10 outcomes and 10 student users
  - create an assignment, aligned to an outcome
  - submit to the assignment with two student users
  - assess the rubrics for each submission in speed grader
  - load LMGB, confirm that all students and outcomes appear,
    with the results of the two students
  - using a tool like Postman, perform an API call with an
    access to the following endpoint:

    http://canvas.docker/api/v1/courses/<course id>/outcome_rollups

  - confirm that a rollup appears for each student, and only scores
    appear for students whose assignments were assessed
  - append "?exclude[]=missing_user_rollups" to the request above
    and resubmit
  - confirm that only rollups with scores appears (should be two)
  - append "&include[]=outcomes" to the request above and resubmit
  - confirm that under the "linked" section, that "outcomes" contains
    all outcomes in the course

Change-Id: I399715093943455659ed5a05c39befca8dc2e801
Reviewed-on: https://gerrit.instructure.com/156247
QA-Review: Dariusz Dzien <ddzien@instructure.com>
Tested-by: Jenkins
Reviewed-by: Neil Gupta <ngupta@instructure.com>
Reviewed-by: Frank Murphy <fmurphy@instructure.com>
Product-Review: Michael Brewer-Davis <mbd@instructure.com>

app/controllers/outcome_results_controller.rb

@@ -265,6 +265,10 @@ class OutcomeResultsController < ApplicationController
   # @argument include[] [String, "courses"|"outcomes"|"outcomes.alignments"|"outcome_groups"|"outcome_links"|"outcome_paths"|"users"]
   #   Specify additional collections to be side loaded with the result.
   #
+  # @argument exclude[] [String, "missing_user_rollups"]
+  #   Specify additional values to exclude. "missing_user_rollups" excludes
+  #   rollups for users without results.
+  #
   # @example_response
   #    {
   #      "rollups": [OutcomeRollup],
@@ -320,8 +324,9 @@ class OutcomeResultsController < ApplicationController
   end
 
   def user_rollups(_opts = {})
+    excludes = Api.value_to_array(params[:exclude]).uniq
     @results = find_results.preload(:user)
-    outcome_results_rollups(@results, @users)
+    outcome_results_rollups(@results, @users, excludes)
   end
 
   def user_rollups_json

lib/outcomes/result_analytics.rb

@@ -68,13 +68,20 @@ module Outcomes
     # users - (Optional) Ensure rollups are included for users in this list.
     #         A listed user with no results will have an empty score array.
     #
+    # excludes - (Optional) Specify additional values to exclude. "missing_user_rollups" excludes
+    #            rollups for users without results.
+    #
     # Returns an Array of Rollup objects.
-    def outcome_results_rollups(results, users=[])
+    def outcome_results_rollups(results, users=[], excludes = [])
       ActiveRecord::Associations::Preloader.new.preload(results, :learning_outcome)
       rollups = results.chunk(&:user_id).map do |_, user_results|
         Rollup.new(user_results.first.user, rollup_user_results(user_results))
       end
-      add_missing_user_rollups(rollups, users)
+      if excludes.include? 'missing_user_rollups'
+        rollups
+      else
+        add_missing_user_rollups(rollups, users)
+      end
     end
 
     # Public: Calculates an average rollup for the specified results

spec/controllers/outcome_results_controller_spec.rb

@@ -200,5 +200,25 @@ describe OutcomeResultsController do
         expect(json['outcome_results'].length).to eq 0
       end
     end
+
+    it 'exclude missing user rollups' do
+      user_session(@teacher)
+      # save a reference to the 1st student
+      student1 = @student
+      # create a 2nd student that is saved as @student
+      student_in_course(active_all: true, course: outcome_course)
+      get 'rollups', params: {:context_id => @course.id,
+                      :course_id => @course.id,
+                      :context_type => "Course",
+                      :user_ids => [student1.id, @student.id],
+                      :outcome_ids => [@outcome.id],
+                      exclude: ['missing_user_rollups']},
+                      format: "json"
+      json = JSON.parse(response.body.gsub("while(1);", ""))
+      # the rollups requests for both students, but excludes the 2nd student
+      # since they do not have any results, unlike the 1st student,
+      # which has a single result in `outcome_result`
+      expect(json['rollups'].length).to be 1
+    end
   end
 end

spec/lib/outcomes/result_analytics_spec.rb

@@ -248,6 +248,15 @@ describe Outcomes::ResultAnalytics do
       end
     end
 
+    it 'excludes missing user rollups' do
+      results = [
+        outcome_from_score(5.0, {user: MockUser[20, 'b']})
+      ]
+      users = [MockUser[10, 'a'], MockUser[30, 'c']]
+      rollups = ra.outcome_results_rollups(results, users, ['missing_user_rollups'])
+      expect(rollups.length).to eq 1
+    end
+
     it 'returns hide_points value of true if all results have hide_points set to true' do
       results = [
         outcome_from_score(4.0,{hide_points: true}),