Merge pull request #1914 from edx/fix/sarina/new_formularesponse_defaults

Fix/sarina/new formularesponse defaults

common/lib/capa/capa/responsetypes.py

@@ -1851,6 +1851,19 @@ class FormulaResponse(LoncapaResponse):
                     'formularesponse: undefined variable in given=%s' % given)
                 raise StudentInputError(
                     "Invalid input: " + uv.message + " not permitted in answer")
+            except ValueError as ve:
+                if 'factorial' in ve.message:
+                    # This is thrown when fact() or factorial() is used in a formularesponse answer
+                    #   that tests on negative and/or non-integer inputs
+                    # ve.message will be: `factorial() only accepts integral values` or `factorial() not defined for negative values`
+                    log.debug(
+                        'formularesponse: factorial function used in response that tests negative and/or non-integer inputs. given={0}'.format(given))
+                    raise StudentInputError(
+                        "factorial function not permitted in answer for this problem. Provided answer was: {0}".format(given))
+                # If non-factorial related ValueError thrown, handle it the same as any other Exception
+                log.debug('formularesponse: error {0} in formula'.format(ve))
+                raise StudentInputError("Invalid input: Could not parse '%s' as a formula" %
+                                        cgi.escape(given))
             except Exception as err:
                 # traceback.print_exc()
                 log.debug('formularesponse: error %s in formula' % err)
@@ -1983,7 +1996,6 @@ class ImageResponse(LoncapaResponse):
         self.ielements = self.inputfields
         self.answer_ids = [ie.get('id') for ie in self.ielements]
 
-
     def get_score(self, student_answers):
         correct_map = CorrectMap()
         expectedset = self.get_mapped_answers()
@@ -2075,8 +2087,6 @@ class ImageResponse(LoncapaResponse):
 
         return answers
 
-
-
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