set root_account_id on custom gradebook column datum model

closes TALLY-696

flag=none

Test Plan:
1. Create some custom gradebook column datum that do not have
   root_account_id set (either create them before checking out this
   patchset, or create them and then force the root_account_id column
   to nil using `update_column`).

2. Verify that the CustomGradebookColumnDataApiController#bulk_update
   API endpoint fills in the root_account_id for the custom column
   data when it is called.

Change-Id: Ia35e2cde1c56be9f07eb97f365f51ec482982db0
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/239035
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Adrian Packel <apackel@instructure.com>
Product-Review: Syed Hussain <shussain@instructure.com>
Reviewed-by: Gary Mei <gmei@instructure.com>
Reviewed-by: Adrian Packel <apackel@instructure.com>

app/models/custom_gradebook_column_datum.rb

@@ -30,6 +30,8 @@ class CustomGradebookColumnDatum < ActiveRecord::Base
     can :update
   end
 
+  before_save :set_root_account_id
+
   def self.queue_bulk_update_custom_columns(context, column_data)
     progress = Progress.create!(context: context, tag: "custom_columns_submissions_update")
     progress.process_job(self, :process_bulk_update_custom_columns, {}, context, column_data)
@@ -37,7 +39,8 @@ class CustomGradebookColumnDatum < ActiveRecord::Base
   end
 
   def self.process_bulk_update_custom_columns(_, context, column_data)
-    Delayed::Batch.serial_batch(priority: Delayed::LOW_PRIORITY, n_strand: ["bulk_update_submissions", context.root_account.global_id]) do
+    root_account = context.root_account
+    Delayed::Batch.serial_batch(priority: Delayed::LOW_PRIORITY, n_strand: ["bulk_update_submissions", root_account.global_id]) do
       custom_gradebook_columns = context.custom_gradebook_columns.preload(:custom_gradebook_column_data)
       column_data.each do |data_point|
         column_id = data_point.fetch(:column_id)
@@ -49,6 +52,7 @@ class CustomGradebookColumnDatum < ActiveRecord::Base
           CustomGradebookColumnDatum.unique_constraint_retry do
             datum = custom_column.custom_gradebook_column_data.find_or_initialize_by(user_id: user_id)
             datum.content = content
+            datum.root_account_id ||= root_account.id
             datum.save!
           end
         else
@@ -57,4 +61,10 @@ class CustomGradebookColumnDatum < ActiveRecord::Base
       end
     end
   end
+
+  private
+
+  def set_root_account_id
+    self.root_account_id ||= custom_gradebook_column&.course&.root_account_id
+  end
 end

spec/models/custom_gradebook_column_datum_spec.rb

@@ -18,9 +18,12 @@
 require_relative '../spec_helper'
 
 describe CustomGradebookColumnDatum do
+  before(:once) do
+    course_with_teacher(active_all: true)
+  end
+
   describe "process_bulk_update_custom_columns" do
-    before :once do
-      course_with_teacher(active_all: true)
+    before(:once) do
       @first_student = student_in_course(active_all: true, course: @course).user
       @second_student = student_in_course(active_all: true, course: @course).user
       @first_col = @course.custom_gradebook_columns.create!(title: "cc1", position: 1)
@@ -50,6 +53,17 @@ describe CustomGradebookColumnDatum do
       ])
     end
 
+    let(:first_student_data) do
+      @course.custom_gradebook_columns.
+        find_by!(id: @first_col.id).
+        custom_gradebook_column_data.
+        find_by(user_id: @first_student.id)
+    end
+
+    it "sets the root account id on the column datum" do
+      expect(first_student_data.root_account_id).to eq @course.root_account.id
+    end
+
     it "adds a datum for a matching student and column" do
       data = @course.custom_gradebook_columns.
         find_by!(id: @first_col.id).
@@ -59,12 +73,7 @@ describe CustomGradebookColumnDatum do
     end
 
     it "checks content exists for the first student in the first column" do
-      data = @course.custom_gradebook_columns.
-        find_by!(id: @first_col.id).
-        custom_gradebook_column_data.
-        find_by!(user_id: @first_student.id).
-        content
-      expect(data).to eql "first column, first student"
+      expect(first_student_data.content).to eql "first column, first student"
     end
 
     it "adds data for multiple students for a column" do
@@ -146,9 +155,51 @@ describe CustomGradebookColumnDatum do
         },
       ])
 
-      data = @course.custom_gradebook_columns.find_by!(id: @first_col.id).
-        custom_gradebook_column_data.find_by(user_id: @first_student.id)
-      expect(data).to be_nil
+      expect(first_student_data).to be_nil
+    end
+  end
+
+  describe "root_account_id" do
+    before(:once) do
+      @column = @course.custom_gradebook_columns.create!(title: "cc1", position: 1)
+      @student = student_in_course(active_all: true, course: @course).user
+    end
+
+    context "on create" do
+      it "sets root_account_id to the course's root_account_id if root_account_id is nil" do
+        datum = @column.custom_gradebook_column_data.create!(content: "some content", user_id: @student.id)
+        expect(datum.root_account_id).to eq @course.root_account_id
+      end
+
+      it "does not modify root_account_id if it is already set" do
+        second_account = account_model
+        datum = @column.custom_gradebook_column_data.create!(
+          content: "some content",
+          user_id: @student.id,
+          root_account_id: second_account.id
+        )
+        expect(datum.root_account_id).to eq second_account.id
+      end
+    end
+
+    context "on update" do
+      it "sets root_account_id to the course's root_account_id if root_account_id is nil" do
+        datum = @column.custom_gradebook_column_data.create!(content: "some content", user_id: @student.id)
+        datum.update_column(:root_account_id, nil)
+        datum.update!(content: "some new content")
+        expect(datum.root_account_id).to eq @course.root_account_id
+      end
+
+      it "does not modify root_account_id if it is already set" do
+        second_account = account_model
+        datum = @column.custom_gradebook_column_data.create!(
+          content: "some content",
+          user_id: @student.id,
+          root_account_id: second_account.id
+        )
+        datum.update!(content: "some new content")
+        expect(datum.root_account_id).to eq second_account.id
+      end
     end
   end
 end