fix resource_link_id in gradespeeder launch

closes QUIZ-8106
flag=none

test plan:
- complete a NQ student submission
- in speedgrader, launch a student submission
- in devtool/network, make sure `context_id` and `resource_link_id` are
  different, and `resource_link_id` is assignment.lti_resource_link_id

Change-Id: I30b2e929bd31e1241776c1ad838432bd8e2e5cec
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/256408
Reviewed-by: Weston Dransfield <wdransfield@instructure.com>
Reviewed-by: Stephen Kacsmark <skacsmark@instructure.com>
QA-Review: Mark McDermott <mmcdermott@instructure.com>
Product-Review: Han Yan <hyan@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>

app/controllers/external_tools_controller.rb

@@ -537,9 +537,15 @@ class ExternalToolsController < ApplicationController
         selected_html: params[:selection],
         domain: HostUrl.context_host(@domain_root_account, request.host)
     }
+
     opts = default_opts.merge(opts)
 
     assignment = api_find(@context.assignments.active, params[:assignment_id]) if params[:assignment_id]
+
+    # from specs, seems this is only a fix for Quizzes Next
+    # resource_link_id in regular QN launches is assignment.lti_resource_link_id
+    opts[:link_code] = @tool.opaque_identifier_for(assignment.external_tool_tag) if assignment.present? && assignment.quiz_lti?
+
     expander = variable_expander(assignment: assignment,
       tool: tool, launch: lti_launch,
       post_message_token: opts[:launch_token],

spec/controllers/external_tools_controller_spec.rb

@@ -916,6 +916,41 @@ describe ExternalToolsController do
       expect(assigns[:lti_launch].params['ext_lti_assignment_id']).to eq lti_assignment_id
     end
 
+    context 'for Quizzes Next launch' do
+      let(:assignment) { assignment_model(course: @course) }
+
+      before do
+        params = {
+          :name => "Quizzes.Next",
+          :url => 'http://example.com/launch',
+          :domain => "example.com",
+          :consumer_key => 'test_key',
+          :shared_secret => 'test_secret',
+          :privacy_level => 'public',
+          :tool_id => 'Quizzes 2'
+        }
+        account.context_external_tools.create!(params)
+        assignment.submission_types = 'external_tool'
+        assignment.external_tool_tag_attributes = {url: "http://example.com/launch"}
+        assignment.save!
+      end
+
+      it 'sets consistent resource_link_id with that in regular lti launch' do
+        u = user_factory(active_all: true)
+        account.account_users.create!(user: u)
+        user_session(@user)
+
+        get :retrieve, params: {
+          course_id: @course.id,
+          assignment_id:assignment.id,
+          url: 'http://example.com/launch'
+        }
+
+        expect(assigns[:lti_launch].params['resource_link_id']).to eq assignment.lti_resource_link_id
+        expect(assigns[:lti_launch].params['context_id']).to eq opaque_id(@course)
+      end
+    end
+
     context 'collaborations' do
       let(:collab) do
         collab = ExternalToolCollaboration.new(