graphql: make assignment override instrumenter work

closes RECNVS-308

Test plan:
  * set up assignments with overrides in a variety of situations
  * assignment dates should be overridden appropriately
  * assignment due dates are *not* overridden when enumerating
    assignmentOverrides

Change-Id: Iefec250bbcf095fb40cfb3b204f3521676e0d9f9
Reviewed-on: https://gerrit.instructure.com/142505
Tested-by: Jenkins
Reviewed-by: Keith T. Garner <[email protected]>
Reviewed-by: Jonathan Featherstone <[email protected]>
QA-Review: Collin Parrish <[email protected]>
Product-Review: Cameron Matheson <[email protected]>

app/graphql/assignment_override_instrumenter.rb

@@ -5,12 +5,6 @@ class AssignmentOverrideInstrumenter
   # overriding assignments only when necessary (for example, when the
   # due date is requested).  Thoughts/potential issues/caveats:
   #
-  # * the implementation of needs_overriding? needs to be done frd.
-  # There are many other factors that should be considered.  At the
-  # very least: when lock_at/unlock_at are requested; if
-  # assignment#only_visible_to_overrides is true.  Probably other
-  # things.
-  #
   # * I love that this automatically applies to assignments no matter
   # where they appear in the schema.  I don't love that this is
   # modifying the resolver of every item in the schema.  The best
@@ -56,8 +50,15 @@ def instrument(type, field)
     end
   end
 
-  # TODO: make this real
+  ATTRIBUTES_NEED_OVERRIDING = %w[dueAt allDay dallDayDate unlockAt lockAt].freeze
+
+  # assignments are automatically overridden in graphql whenever one of the
+  # dueAt/lockAt/unlockAt fields are requested *UNLESS* the user is also
+  # requesting the list of assignment_overrides.  The rationale is that the
+  # user won't have a way of seeing the assignment's default due date if it's
+  # overriden
   def self.needs_overriding?(selections)
-    selections.key? "dueAt"
+    ATTRIBUTES_NEED_OVERRIDING.any? { |attr| selections.key?(attr) } &&
+      !selections.key?("assignmentOverrides")
   end
 end

spec/graphql/assignment_override_instrumenter_spec.rb

@@ -0,0 +1,45 @@
+#
+# Copyright (C) 2018 Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+require File.expand_path(File.dirname(__FILE__) + '/../spec_helper.rb')
+
+describe AssignmentOverrideInstrumenter do
+  context '#needs_overriding?' do
+    it "doesn't override when no overrideable attributes are requested" do
+      expect(
+        AssignmentOverrideInstrumenter.needs_overriding?("id" => true)
+      ).to eq false
+    end
+
+    it "overrides when overrideable attributes are requested" do
+      %w[dueAt unlockAt lockAt].each { |overrideable_attribute|
+        expect(
+          AssignmentOverrideInstrumenter.needs_overriding?(overrideable_attribute => true)
+        ).to eq true
+      }
+    end
+
+    it "doesn't override if assignment_overrides are requested" do
+      expect(
+        AssignmentOverrideInstrumenter.needs_overriding?(
+          "dueAt" => true, "assignmentOverrides" => true
+        )
+      ).to eq false
+    end
+  end
+end