Add handler to receive completion events

* Submit a completion when receiving a completion event from an XBlock.
* Handle legacy progress events.
* Convert handler to use a dispatch dict instead of an if-else chain.
* Extract masquerade checking from individual handlers.
* Gate submit_completion on waffle switch
* 404 on handler views when trying to submit completion without waffle
switch enabled.

OC-3087

Disallow calling submit_completion when waffle flag is disabled.

Add tests that trying to publish completion errors.

lms/djangoapps/completion/models.py

@@ -12,6 +12,7 @@ from model_utils.models import TimeStampedModel
 from opaque_keys.edx.keys import CourseKey
 
 from openedx.core.djangoapps.xmodule_django.models import CourseKeyField, UsageKeyField
+from . import waffle
 
 # pylint: disable=ungrouped-imports
 try:
@@ -52,7 +53,8 @@ class BlockCompletionManager(models.Manager):
 
         Return Value:
             (BlockCompletion, bool): A tuple comprising the created or updated
-            BlockCompletion object and a boolean value indicating whether the value
+            BlockCompletion object and a boolean value indicating whether the
+            object was newly created by this call.
 
         Raises:
 
@@ -84,17 +86,23 @@ class BlockCompletionManager(models.Manager):
                 "block_key must be an instance of `opaque_keys.edx.keys.UsageKey`.  Got {}".format(type(block_key))
             )
 
-        obj, isnew = self.get_or_create(
-            user=user,
-            course_key=course_key,
-            block_type=block_type,
-            block_key=block_key,
-            defaults={'completion': completion},
-        )
-        if not isnew and obj.completion != completion:
-            obj.completion = completion
-            obj.full_clean()
-            obj.save()
+        if waffle.waffle().is_enabled(waffle.ENABLE_COMPLETION_TRACKING):
+            obj, isnew = self.get_or_create(
+                user=user,
+                course_key=course_key,
+                block_type=block_type,
+                block_key=block_key,
+                defaults={'completion': completion},
+            )
+            if not isnew and obj.completion != completion:
+                obj.completion = completion
+                obj.full_clean()
+                obj.save()
+        else:
+            # If the feature is not enabled, this method should not be called.  Error out with a RuntimeError.
+            raise RuntimeError(
+                "BlockCompletion.objects.submit_completion should not be called when the feature is disabled."
+            )
         return obj, isnew
 
 

lms/djangoapps/completion/tests/test_models.py

@@ -2,6 +2,8 @@
 Test models, managers, and validators.
 """
 
+from __future__ import absolute_import, division, print_function, unicode_literals
+
 from django.core.exceptions import ValidationError
 from django.test import TestCase
 from opaque_keys.edx.keys import UsageKey
@@ -9,6 +11,7 @@ from opaque_keys.edx.keys import UsageKey
 from student.tests.factories import UserFactory
 
 from .. import models
+from .. import waffle
 
 
 class PercentValidatorTestCase(TestCase):
@@ -24,13 +27,8 @@ class PercentValidatorTestCase(TestCase):
             self.assertRaises(ValidationError, models.validate_percent, value)
 
 
-class SubmitCompletionTestCase(TestCase):
-    """
-    Test that BlockCompletion.objects.submit_completion has the desired
-    semantics.
-    """
-    def setUp(self):
-        super(SubmitCompletionTestCase, self).setUp()
+class CompletionSetUpMixin(object):
+    def set_up_completion(self):
         self.user = UserFactory()
         self.block_key = UsageKey.from_string(u'block-v1:edx+test+run+type@video+block@doggos')
         self.completion = models.BlockCompletion.objects.create(
@@ -41,6 +39,19 @@ class SubmitCompletionTestCase(TestCase):
             completion=0.5,
         )
 
+
+class SubmitCompletionTestCase(CompletionSetUpMixin, TestCase):
+    """
+    Test that BlockCompletion.objects.submit_completion has the desired
+    semantics.
+    """
+    def setUp(self):
+        super(SubmitCompletionTestCase, self).setUp()
+        self._overrider = waffle.waffle().override(waffle.ENABLE_COMPLETION_TRACKING, True)
+        self._overrider.__enter__()
+        self.addCleanup(self._overrider.__exit__, None, None, None)
+        self.set_up_completion()
+
     def test_changed_value(self):
         with self.assertNumQueries(4):  # Get, update, 2 * savepoints
             completion, isnew = models.BlockCompletion.objects.submit_completion(
@@ -102,3 +113,32 @@ class SubmitCompletionTestCase(TestCase):
         completion = models.BlockCompletion.objects.get(user=self.user, block_key=self.block_key)
         self.assertEqual(completion.completion, 0.5)
         self.assertEqual(models.BlockCompletion.objects.count(), 1)
+
+
+class CompletionDisabledTestCase(CompletionSetUpMixin, TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        super(CompletionDisabledTestCase, cls).setUpClass()
+        cls.overrider = waffle.waffle().override(waffle.ENABLE_COMPLETION_TRACKING, False)
+        cls.overrider.__enter__()
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.overrider.__exit__(None, None, None)
+        super(CompletionDisabledTestCase, cls).tearDownClass()
+
+    def setUp(self):
+        super(CompletionDisabledTestCase, self).setUp()
+        self.set_up_completion()
+
+    def test_cannot_call_submit_completion(self):
+        self.assertEqual(models.BlockCompletion.objects.count(), 1)
+        with self.assertRaises(RuntimeError):
+            models.BlockCompletion.objects.submit_completion(
+                user=self.user,
+                course_key=self.block_key.course_key,
+                block_key=self.block_key,
+                completion=0.9,
+            )
+        self.assertEqual(models.BlockCompletion.objects.count(), 1)

lms/djangoapps/completion/waffle.py

@@ -0,0 +1,20 @@
+"""
+This module contains various configuration settings via
+waffle switches for the completion app.
+"""
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from openedx.core.djangoapps.waffle_utils import WaffleSwitchNamespace
+
+# Namespace
+WAFFLE_NAMESPACE = 'completion'
+
+# Switches
+ENABLE_COMPLETION_TRACKING = 'enable_completion_tracking'
+
+
+def waffle():
+    """
+    Returns the namespaced, cached, audited Waffle class for completion.
+    """
+    return WaffleSwitchNamespace(name=WAFFLE_NAMESPACE, log_prefix='completion: ')