Add correct answer to response

common/lib/capa/capa/capa_problem.py

@@ -495,6 +495,27 @@ class LoncapaProblem(object):
             answer_ids.append(results.keys())
         return answer_ids
 
+    def find_correct_answer_text(self, answer_id):
+        """
+        Returns the correct answer(s) for the provided answer_id as a single string.
+
+        Arguments::
+            answer_id (str): a string like "98e6a8e915904d5389821a94e48babcf_13_1"
+
+        Returns:
+            str: A string containing the answer or multiple answers separated by commas.
+        """
+        xml_elements = self.tree.xpath('//*[@id="' + answer_id + '"]')
+        if not xml_elements:
+            return
+        xml_element = xml_elements[0]
+        answer_text = xml_element.xpath('@answer')
+        if answer_text:
+            return answer_id[0]
+        if xml_element.tag == 'optioninput':
+            return xml_element.xpath('@correct')[0]
+        return ', '.join(xml_element.xpath('*[@correct="true"]/text()'))
+
     def find_question_label(self, answer_id):
         """
         Obtain the most relevant question text for a particular answer.

common/lib/capa/capa/tests/test_capa_problem.py

@@ -659,6 +659,44 @@ class CAPAProblemReportHelpersTest(unittest.TestCase):
         )
         self.assertEquals(problem.find_answer_text(answer_id, choice_id), answer_text)
 
+    @ddt.data(
+        # Test for ChoiceResponse
+        ('1_2_1', 'over-suspicious'),
+        # Test for MultipleChoiceResponse
+        ('1_3_1', 'The iPad, Napster'),
+        # Test for OptionResponse
+        ('1_4_1', 'blue'),
+    )
+    @ddt.unpack
+    def test_find_correct_answer_text_choices(self, answer_id, answer_text):
+        """
+        Verify that ``find_correct_answer_text`` can find the correct answer for
+        ChoiceResponse, MultipleChoiceResponse and OptionResponse problems.
+        """
+        problem = new_loncapa_problem(
+            """
+            <problem>
+                <choiceresponse>
+                    <checkboxgroup label="Select the correct synonym of paranoid?">
+                        <choice correct="true">over-suspicious</choice>
+                        <choice correct="false">funny</choice>
+                    </checkboxgroup>
+                </choiceresponse>
+                <multiplechoiceresponse>
+                    <choicegroup type="MultipleChoice">
+                        <choice correct="true">The iPad</choice>
+                        <choice correct="true">Napster</choice>
+                        <choice correct="false">The iPod</choice>
+                    </choicegroup>
+                </multiplechoiceresponse>
+                <optionresponse>
+                    <optioninput options="('yellow','blue','green')" correct="blue" label="Color_1"/>
+                </optionresponse>
+            </problem>
+            """
+        )
+        self.assertEquals(problem.find_correct_answer_text(answer_id), answer_text)
+
     def test_find_answer_text_textinput(self):
         problem = new_loncapa_problem(
             """

common/lib/xmodule/xmodule/capa_module.py

@@ -393,13 +393,17 @@ class CapaDescriptor(CapaFields, RawDescriptor):
 
                 question_text = lcp.find_question_label(answer_id)
                 answer_text = lcp.find_answer_text(answer_id, current_answer=orig_answers)
+                correct_answer_text = lcp.find_correct_answer_text(answer_id)
 
                 count += 1
-                yield (user_state.username, {
+                report = {
                     _("Answer ID"): answer_id,
                     _("Question"): question_text,
                     _("Answer"): answer_text,
-                })
+                }
+                if correct_answer_text is not None:
+                    report[_("Correct Answer")] = correct_answer_text
+                yield (user_state.username, report)
 
     # Proxy to CapaModule for access to any of its attributes
     answer_available = module_attr('answer_available')

lms/djangoapps/instructor_task/tests/test_tasks_helper.py

@@ -598,6 +598,7 @@ class TestProblemResponsesReport(TestReportMixin, InstructorTaskModuleTestCase):
             'title': 'Problem1',
             'Answer ID': 'i4x-edx-1_23x-problem-Problem1_2_1',
             'Answer': 'Option 1',
+            'Correct Answer': u'Option 1',
             'Question': u'The correct answer is Option 1',
         }, student_data[0])
         self.assertIn('state', student_data[0])