allow capa poroblems access to anonymous_student_id

fix system->capa_system in capa_problem change for anonid

common/lib/capa/capa/capa_problem.py

@@ -620,6 +620,7 @@ class LoncapaProblem(object):
         """
         context = {}
         context['seed'] = self.seed
+        context['anonymous_student_id'] = self.capa_system.anonymous_student_id
         all_code = ''
 
         python_path = []

common/lib/capa/capa/tests/test_html_render.py

@@ -73,6 +73,24 @@ class CapaHtmlRenderTest(unittest.TestCase):
         span_element = rendered_html.find('span')
         self.assertEqual(span_element.text, 'Test text')
 
+    def test_anonymous_student_id(self):
+        # make sure anonymous_student_id is rendered properly as a context variable
+        xml_str = textwrap.dedent("""
+            <problem>
+            <span>Welcome $anonymous_student_id</span>
+            </problem>
+        """)
+
+        # Create the problem
+        problem = new_loncapa_problem(xml_str)
+
+        # Render the HTML
+        rendered_html = etree.XML(problem.get_html())
+
+        # Expect that the anonymous_student_id was converted to "student"
+        span_element = rendered_html.find('span')
+        self.assertEqual(span_element.text, 'Welcome student')
+
     def test_render_script(self):
         # Generate some XML with a <script> tag
         xml_str = textwrap.dedent("""