Ensure cursor is converted into integer as needed

To ensure #339's change to string cursors can occur smoothly, we ensure
we always convert the cursor into an integer when needed.

Specifically, the Array and CSV cursors MUST be integers when forwarded
to JobIteration's enumerator builders, or things break. The ActiveRecord
enumerator builder handles the conversion gracefully.

This should allow consumers to perform the cursor schema change from
bigint to string without worrying about stale code blowing up.

app/jobs/maintenance_tasks/task_job.rb

@@ -33,9 +33,12 @@ def build_enumerator(_run, cursor:)
       when ActiveRecord::Relation
         enumerator_builder.active_record_on_records(collection, cursor: cursor)
       when Array
-        enumerator_builder.build_array_enumerator(collection, cursor: cursor)
+        enumerator_builder.build_array_enumerator(
+          collection,
+          cursor: cursor&.to_i,
+        )
       when CSV
-        JobIteration::CsvEnumerator.new(collection).rows(cursor: cursor)
+        JobIteration::CsvEnumerator.new(collection).rows(cursor: cursor&.to_i)
       else
         raise ArgumentError, "#{@task.class.name}#collection must be either "\
           'an Active Record Relation, Array, or CSV.'

test/jobs/maintenance_tasks/task_job_test.rb

@@ -198,6 +198,15 @@ class TaskJobTest < ActiveJob::TestCase
       TaskJob.perform_now(@run)
     end
 
+    # Remove this once string cursors are shipped (#339)
+    test '.perform_now handles string cursor when Array task resumes' do
+      @run.expects(:cursor).returns('0')
+
+      TaskJob.perform_now(@run)
+
+      assert_predicate @run, :succeeded?
+    end
+
     test '.perform_now accepts Active Record Relations as collection' do
       Maintenance::TestTask.any_instance.stubs(collection: Post.all)
       Maintenance::TestTask.any_instance.expects(:process).times(Post.count)
@@ -207,6 +216,16 @@ class TaskJobTest < ActiveJob::TestCase
       assert_predicate @run.reload, :succeeded?
     end
 
+    # Remove this once string cursors are shipped (#339)
+    test '.perform_now handles string cursor when Active Record Relation task resumes' do
+      run = Run.create!(task_name: 'Maintenance::UpdatePostsTask')
+      run.expects(:cursor).returns(Post.pick(:id)&.to_s)
+
+      TaskJob.perform_now(run)
+
+      assert_predicate run, :succeeded?
+    end
+
     test '.perform_now accepts CSVs as collection' do
       Maintenance::ImportPostsTask.any_instance.expects(:process).times(5)
 
@@ -220,6 +239,20 @@ class TaskJobTest < ActiveJob::TestCase
       assert_predicate run.reload, :succeeded?
     end
 
+    # Remove this once string cursors are shipped (#339)
+    test '.perform_now handles string cursor when CSV task resumes' do
+      run = Run.new(task_name: 'Maintenance::ImportPostsTask')
+      run.csv_file.attach(
+        { io: File.open(file_fixture('sample.csv')), filename: 'sample.csv' }
+      )
+      run.save
+      run.expects(:cursor).returns('0')
+
+      TaskJob.perform_now(run)
+
+      assert_predicate run, :succeeded?
+    end
+
     test '.perform_now sets the Run as errored when the Task collection is invalid' do
       Maintenance::TestTask.any_instance.stubs(collection: 'not a collection')