Allows ChoiceResponse CAPA problems to use script-computed variables to

determine choice correctness, as MultipleChoiceResponse problems already do.

Adds a unit test for this change, and for the existing MultipleChoiceResponse
computed correctness capability.

common/lib/capa/capa/responsetypes.py

@@ -851,31 +851,30 @@ class ChoiceResponse(LoncapaResponse):
     def setup_response(self):
         self.assign_choice_names()
 
-        correct_xml = self.xml.xpath(
-            '//*[@id=$id]//choice[@correct="true"]',
-            id=self.xml.get('id')
-        )
+        self.correct_choices = set()
+        self.incorrect_choices = set()
+        for choice in self.get_choices():
 
-        self.correct_choices = set([
-            choice.get('name') for choice in correct_xml
-        ])
+            # contextualize the name and correct attributes
+            name = contextualize_text(choice.get('name'), self.context)
+            correct = contextualize_text(choice.get('correct'), self.context).upper()
 
-        incorrect_xml = self.xml.xpath(
-            '//*[@id=$id]//choice[@correct="false"]',
-            id=self.xml.get('id')
-        )
+            # divide choices into correct and incorrect
+            if correct == 'TRUE':
+                self.correct_choices.add(name)
+            elif correct == 'FALSE':
+                self.incorrect_choices.add(name)
 
-        self.incorrect_choices = set([
-            choice.get('name') for choice in incorrect_xml
-        ])
+    def get_choices(self):
+        """Returns this response's XML choice elements."""
+        return self.xml.xpath('//*[@id=$id]//choice', id=self.xml.get('id'))
 
     def assign_choice_names(self):
         """
         Initialize name attributes in <choice> tags for this response.
         """
 
-        for index, choice in enumerate(self.xml.xpath('//*[@id=$id]//choice',
-                                                      id=self.xml.get('id'))):
+        for index, choice in enumerate(self.get_choices()):
             choice.set("name", "choice_" + str(index))
             # If a choice does not have an id, assign 'A' 'B', .. used by CompoundHint
             if not choice.get('id'):

common/lib/capa/capa/tests/response_xml_factory.py

@@ -172,6 +172,8 @@ class ResponseXMLFactory(object):
                 correctness = 'false'
             elif 'partial' in correct_val:
                 correctness = 'partial'
+            else:
+                correctness = correct_val
 
             choice_element.set('correct', correctness)
 

common/lib/capa/capa/tests/test_responsetypes.py

@@ -169,6 +169,35 @@ class MultiChoiceResponseTest(ResponseTest):  # pylint: disable=missing-docstrin
         correct_map = problem.grade_answers({'1_2_1': 'choice_2'})
         self.assertAlmostEqual(correct_map.get_npoints('1_2_1'), 0)
 
+    def test_contextualized_choices(self):
+        script = textwrap.dedent("""
+            a = 2
+            b = 9
+            c = a + b
+
+            ok0 = c % 2 == 0 # check remainder modulo 2
+            text0 = "$a + $b is even"
+
+            ok1 = c % 2 == 1 # check remainder modulo 2
+            text1 = "$a + $b is odd"
+
+            ok2 = "partial"
+            text2 = "infinity may be both"
+        """)
+        choices = ["$ok0", "$ok1", "$ok2"]
+        choice_names = ["$text0 ... (should be $ok0)",
+                        "$text1 ... (should be $ok1)",
+                        "$text2 ... (should be $ok2)"]
+        problem = self.build_problem(script=script,
+                                     choices=choices,
+                                     choice_names=choice_names,
+                                     credit_type='points')
+
+        # Ensure the expected correctness and choice names
+        self.assert_grade(problem, 'choice_2 + 9 is even ... (should be False)', 'incorrect')
+        self.assert_grade(problem, 'choice_2 + 9 is odd ... (should be True)', 'correct')
+        self.assert_grade(problem, 'choice_infinity may be both ... (should be partial)', 'partially-correct')
+
 
 class TrueFalseResponseTest(ResponseTest):  # pylint: disable=missing-docstring
     xml_factory_class = TrueFalseResponseXMLFactory
@@ -1292,6 +1321,26 @@ class ChoiceResponseTest(ResponseTest):  # pylint: disable=missing-docstring
         correct_map = problem.grade_answers({})
         self.assertEqual(correct_map.get_correctness('1_2_1'), 'incorrect')
 
+    def test_contextualized_choices(self):
+        script = textwrap.dedent("""
+            a = 6
+            b = 4
+            c = a + b
+
+            ok0 = c % 2 == 0 # check remainder modulo 2
+            ok1 = c % 3 == 0 # check remainder modulo 3
+            ok2 = c % 5 == 0 # check remainder modulo 5
+            ok3 = not any([ok0, ok1, ok2])
+        """)
+        choices = ["$ok0", "$ok1", "$ok2", "$ok3"]
+        problem = self.build_problem(script=script,
+                                     choice_type='checkbox',
+                                     choices=choices)
+
+        # Ensure the expected correctness
+        self.assert_grade(problem, ['choice_0', 'choice_2'], 'correct')
+        self.assert_grade(problem, ['choice_1', 'choice_3'], 'incorrect')
+
 
 class JavascriptResponseTest(ResponseTest):  # pylint: disable=missing-docstring
     xml_factory_class = JavascriptResponseXMLFactory