Trust information from the launch instead of the DB for is_gradable

We use assignment.is_gradable for record keeping but ultimately the
source of truth should be the current launch. If we don't have the
necessary parameters to call the grading APIs, it's not a gradable launch.

The discrepancy of both method for `is_gradable` comes (as far as we know) from SpeedGrader launches
which are always not gradable (!?) and confuse the course and assignment
parameters.

After 387ec0a we stopped recording that
bogus data in the DB. As a result of that assignment are correctly
marked as gradable in the DB but launches by students in the "submission
details" view (which used SpeedGrader launches) fail because they are in
fact, not gradable launches.

lms/product/canvas/_plugin/misc.py

@@ -24,7 +24,7 @@ def post_launch_assignment_hook(self, request, js_config, assignment):
         # `lis_result_sourcedid` associates a specific user with an
         # assignment.
         if (
-            assignment.is_gradable
+            self.is_assignment_gradable(lti_params)
             and lti_user.is_learner
             and lti_params.get("lis_result_sourcedid")
         ):

tests/unit/lms/product/canvas/_plugin/misc_test.py

@@ -1,4 +1,4 @@
-from unittest.mock import create_autospec, sentinel
+from unittest.mock import create_autospec, patch, sentinel
 
 import pytest
 
@@ -25,16 +25,18 @@ def test_post_launch_assignment_hook(
         is_learner,
         grading_id,
         focused_user,
+        is_assignment_gradable,
     ):
-        assignment = factories.Assignment(is_gradable=is_gradable)
+        assignment = factories.Assignment()
         pyramid_request.lti_params["lis_result_sourcedid"] = grading_id
         pyramid_request.params["focused_user"] = focused_user
+        is_assignment_gradable.return_value = is_gradable
         if is_learner:
             request.getfixturevalue("user_is_learner")
 
         plugin.post_launch_assignment_hook(pyramid_request, js_config, assignment)
 
-        if assignment.is_gradable and is_learner and grading_id:
+        if is_gradable and is_learner and grading_id:
             js_config.add_canvas_speedgrader_settings.assert_called_once_with(
                 assignment.document_url
             )
@@ -179,6 +181,14 @@ def test_get_deep_linked_assignment_configuration(
         else:
             assert "url" not in result
 
+    @pytest.mark.parametrize(
+        "get,expected", [({}, False), ({"learner_canvas_user_id": "ID"}, True)]
+    )
+    def test_is_speed_grader_launch(self, get, expected, plugin, pyramid_request):
+        pyramid_request.GET = get
+
+        assert plugin.is_speed_grader_launch(pyramid_request) == expected
+
     def test_factory(self, pyramid_request):
         plugin = CanvasMiscPlugin.factory(sentinel.context, pyramid_request)
         assert isinstance(plugin, CanvasMiscPlugin)
@@ -194,3 +204,8 @@ def js_config(self):
     @pytest.fixture
     def VSBookLocation(self, patch):
         return patch("lms.product.canvas._plugin.misc.VSBookLocation")
+
+    @pytest.fixture
+    def is_assignment_gradable(self, plugin):
+        with patch.object(plugin, "is_assignment_gradable") as is_assignment_gradable:
+            yield is_assignment_gradable