graphql: add grading_type to assignments

closes RECNVS-276

Test plan:
  * query assignment grading_types in graphql

Change-Id: I37e607f41fbb7ab27d4de663a1ff244f4c52479a
Reviewed-on: https://gerrit.instructure.com/139655
Tested-by: Jenkins
Reviewed-by: Michael Jasper <mjasper@instructure.com>
QA-Review: Collin Parrish <cparrish@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>

app/graphql/types/assignment_type.rb

@@ -64,6 +64,10 @@ module Types
       end
     end
 
+    field :gradingType, AssignmentGradingType, resolve: ->(assignment, _, _) {
+      GRADING_TYPES[assignment.grading_type]
+    }
+
     field :submissionTypes, types[!AssignmentSubmissionType],
       resolve: ->(assignment, _, _) {
         # there's some weird data in the db so we'll just ignore anything that
@@ -140,6 +144,10 @@ module Types
     wiki_page
   ].to_set
 
+  GRADING_TYPES = Hash[
+    Assignment::ALLOWED_GRADING_TYPES.zip(Assignment::ALLOWED_GRADING_TYPES)
+  ]
+
   AssignmentSubmissionType = GraphQL::EnumType.define do
     name "SubmissionType"
     description "Types of submissions an assignment accepts"
@@ -147,4 +155,9 @@ module Types
       value(submission_type)
     }
   end
+
+  AssignmentGradingType = GraphQL::EnumType.define do
+    name "GradingType"
+    Assignment::ALLOWED_GRADING_TYPES.each { |type| value(type) }
+  end
 end

schema.graphql

@@ -27,6 +27,7 @@ type Assignment implements Node, Timestamped {
 
   # when this assignment is due
   dueAt: String
+  gradingType: GradingType
   htmlUrl: URL
   id: ID!
   name: String
@@ -415,6 +416,15 @@ type GradingPeriodEdge {
   node: GradingPeriod
 }
 
+enum GradingType {
+  gpa_scale
+  letter_grade
+  not_graded
+  pass_fail
+  percent
+  points
+}
+
 type Group implements Timestamped {
   # legacy canvas id
   _id: ID!

spec/graphql/types/assignment_type_spec.rb

@@ -84,4 +84,11 @@ describe Types::AssignmentType do
     assignment.update_attribute :submission_types, "none,foodfight"
     expect(assignment_type.submissionTypes).to eq ["none"]
   end
+
+  it "returns (valid) grading types" do
+    expect(assignment_type.gradingType).to eq assignment.grading_type
+
+    assignment.update_attribute :grading_type, "fakefakefake"
+    expect(assignment_type.gradingType).to be_nil
+  end
 end