graphql: add some top-level fields

These objects were originally accessible via the node/legacyNode, but
these first-class fields will be a bit more convenient to use.

Test plan:
  * retrieve objects from the top-level
    course/assignment/assignmentGroup fields

Change-Id: I6f64a0841a36dabd753e8e91aa4145689d56fc1b
Reviewed-on: https://gerrit.instructure.com/167469
Reviewed-by: Carl Kibler <ckibler@instructure.com>
Tested-by: Jenkins
QA-Review: Cameron Matheson <cameron@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>

app/graphql/types/query_type.rb

@@ -31,6 +31,30 @@ def legacy_node(type:, _id:)
       GraphQLNodeLoader.load(type, _id, context)
     end
 
+    field :course, Types::CourseType, null: true do
+      argument :id, ID, "a graphql or legacy id", required: true,
+        prepare: GraphQLHelpers.relay_or_legacy_id_prepare_func("Course")
+    end
+    def course(id:)
+      GraphQLNodeLoader.load("Course", id, context)
+    end
+
+    field :assignment, Types::AssignmentType, null: true do
+      argument :id, ID, "a graphql or legacy id", required: true,
+        prepare: GraphQLHelpers.relay_or_legacy_id_prepare_func("Course")
+    end
+    def assignment(id:)
+      GraphQLNodeLoader.load("Assignment", id, context)
+    end
+
+    field :assignment_group, Types::AssignmentGroupType, null: true do
+      argument :id, ID, "a graphql or legacy id", required: true,
+        prepare: GraphQLHelpers.relay_or_legacy_id_prepare_func("Course")
+    end
+    def assignment_group(id:)
+      GraphQLNodeLoader.load("AssignmentGroup", id, context)
+    end
+
     field :all_courses, [CourseType],
       "All courses viewable by the current user",
       null: true

schema.graphql

@@ -747,6 +747,18 @@ type PageViewAnalysis {
 type Query {
   # All courses viewable by the current user
   allCourses: [Course!]
+  assignment(
+    # a graphql or legacy id
+    id: ID!
+  ): Assignment
+  assignmentGroup(
+    # a graphql or legacy id
+    id: ID!
+  ): AssignmentGroup
+  course(
+    # a graphql or legacy id
+    id: ID!
+  ): Course
 
   # Fetches an object given its type and legacy ID
   legacyNode(_id: ID!, type: NodeType!): Node

spec/graphql/types/assignment_group_type_spec.rb

@@ -37,6 +37,19 @@
       @group_type = GraphQLTypeTester.new(@group, current_user: @student)
     end
 
+    context "top-level permissions" do
+      it "needs read permission" do
+        some_person = user_factory(active_all: true)
+        expect(@group_type.resolve("_id", current_user: some_person)).to be_nil
+
+        expect(
+          CanvasSchema.execute(<<~GQL, context: {current_user: some_person}).dig("data", "ag")
+            query { ag: assignmentGroup(id: "#{@group.id}") { id } }
+          GQL
+        ).to be_nil
+      end
+    end
+
     it "returns information about the group" do
       expect(@group_type.resolve("_id")).to eq @group.id.to_s
       expect(@group_type.resolve("name")).to eq @group.name

spec/graphql/types/assignment_type_spec.rb

@@ -43,9 +43,20 @@
     expect(assignment_type.resolve("muted")).to eq assignment.muted?
   end
 
-  it "requires read permission" do
-    assignment.unpublish
-    expect(assignment_type.resolve("_id")).to be_nil
+  context "top-level permissions" do
+    it "requires read permission" do
+      assignment.unpublish
+
+      # node / legacy node
+      expect(assignment_type.resolve("_id")).to be_nil
+
+      # assignment
+      expect(
+        CanvasSchema.execute(<<~GQL, context: {current_user: student}).dig("data", "assignment")
+          query { assignment(id: "#{assignment.id.to_s}") { id } }
+        GQL
+      ).to be_nil
+    end
   end
 
   it "returns needsGradingCount" do

spec/graphql/types/course_type_spec.rb

@@ -33,11 +33,21 @@
     expect(course_type.resolve("name")).to eq course.name
   end
 
-  it "needs read permission" do
-    course_with_student
-    @course2, @student2 = @course, @student
+  context "top-level permissions" do
+    it "needs read permission" do
+      course_with_student
+      @course2, @student2 = @course, @student
 
-    expect(course_type.resolve("_id", current_user: @student2)).to be_nil
+      # node / legacy node
+      expect(course_type.resolve("_id", current_user: @student2)).to be_nil
+
+      # course
+      expect(
+        CanvasSchema.execute(<<~GQL, context: {current_user: @student2}).dig("data", "course")
+          query { course(id: "#{course.id.to_s}") { id } }
+        GQL
+      ).to be_nil
+    end
   end
 
   describe "assignmentsConnection" do