adding first attempted timestamp to subsection grades

for TNL-5895

lms/djangoapps/grades/migrations/0008_persistentsubsectiongrade_first_attempted.py

+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('grades', '0007_add_passed_timestamp_column'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='persistentsubsectiongrade',
+            name='first_attempted',
+            field=models.DateTimeField(null=True, blank=True),
+        ),
+    ]

lms/djangoapps/grades/models.py

@@ -236,6 +236,11 @@ class PersistentSubsectionGrade(TimeStampedModel):
     earned_graded = models.FloatField(blank=False)
     possible_graded = models.FloatField(blank=False)
 
+    # timestamp for the learner's first attempt at content in
+    # this subsection. If null, indicates no attempt
+    # has yet been made.
+    first_attempted = models.DateTimeField(null=True, blank=True)
+
     # track which blocks were visible at the time of grade calculation
     visible_blocks = models.ForeignKey(VisibleBlocks, db_column='visible_blocks_hash', to_field='hashed')
 
@@ -253,7 +258,9 @@ class PersistentSubsectionGrade(TimeStampedModel):
         """
         Returns a string representation of this model.
         """
-        return u"{} user: {}, course version: {}, subsection {} ({}). {}/{} graded, {}/{} all".format(
+        return (
+            u"{} user: {}, course version: {}, subsection: {} ({}). {}/{} graded, {}/{} all, first_attempted: {}"
+        ).format(
             type(self).__name__,
             self.user_id,
             self.course_version,
@@ -263,6 +270,7 @@ class PersistentSubsectionGrade(TimeStampedModel):
             self.possible_graded,
             self.earned_all,
             self.possible_all,
+            self.first_attempted,
         )
 
     @classmethod

lms/djangoapps/grades/tests/test_models.py

@@ -210,6 +210,7 @@ class PersistentSubsectionGradeTest(GradesModelTestCase):
             "earned_graded": 6.0,
             "possible_graded": 8.0,
             "visible_blocks": self.block_records,
+            "first_attempted": "2016-08-01 18:53:24.354741",
         }
 
     def test_create(self):
@@ -235,10 +236,27 @@ class PersistentSubsectionGradeTest(GradesModelTestCase):
         with self.assertRaises(IntegrityError):
             PersistentSubsectionGrade.create_grade(**self.params)
 
-    def test_course_version_is_optional(self):
-        del self.params["course_version"]
+    @ddt.data("course_version", "first_attempted")
+    def test_optional_fields(self, field):
+        del self.params[field]
         PersistentSubsectionGrade.create_grade(**self.params)
 
+    @ddt.data(
+        ("user_id", IntegrityError),
+        ("usage_key", KeyError),
+        ("subtree_edited_timestamp", IntegrityError),
+        ("earned_all", IntegrityError),
+        ("possible_all", IntegrityError),
+        ("earned_graded", IntegrityError),
+        ("possible_graded", IntegrityError),
+        ("visible_blocks", KeyError),
+    )
+    @ddt.unpack
+    def test_non_optional_fields(self, field, error):
+        del self.params[field]
+        with self.assertRaises(error):
+            PersistentSubsectionGrade.create_grade(**self.params)
+
     @ddt.data(True, False)
     def test_update_or_create_grade(self, already_created):
         created_grade = PersistentSubsectionGrade.create_grade(**self.params) if already_created else None