parsing and converting curly bracket variable names on client side

cms/static/grammars/main.jspeg

@@ -22,7 +22,7 @@ KeyValueString
     }
 
 KeyValuePair
-  = key:KeyValueString _ ':' _ value:KeyValueString
+  = key:KeyValueString ' '* ':' ' '* value:KeyValueString
     {
       return {'key': key, 'value': value};
     } 
@@ -70,7 +70,7 @@ ImageTitle
     }
 
 Image
-  = ImageIdentifier title:ImageTitle? _ '(' _ url:ImageLink ')' ' '* Linebreak
+  = ImageIdentifier title:ImageTitle? ' '* '(' ' '* url:ImageLink ')' ' '* Linebreak
     {
       return {'type': 'image', 'url': url, 'title': title};
     }
@@ -91,14 +91,24 @@ CorrectAnswerIdentifier
 
 /* StringResponse */
 
+QuotedVariableName
+  = '"' name:VariableName '"'    { return name; }
+  / '\'' name:VariableName '\''    { return name; }
+
+VariableName
+  = '{' chars:([a-zA-Z0-9_]+) '}'
+    {
+      return '{' + chars.join("") + '}'
+    }
+
 StringResponse
-  = CorrectAnswerIdentifier _ !'(' value:(QuotedString / Text) Linebreak
+  = CorrectAnswerIdentifier ' '* !'(' value:(QuotedString / QuotedVariableName / Text) Linebreak
     {
       return {'type': 'string', 'answer': $.trim(value)};
     }
 
 NumericalOrStringResponse
-  = CorrectAnswerIdentifier _ value:NumericalValue _ tolerance:NumericalTolerance? _ Linebreak
+  = CorrectAnswerIdentifier ' '* value:NumericalValue ' '* tolerance:NumericalTolerance? ' '* Linebreak
     {
       if (tolerance == "")
         tolerance = "5%"
@@ -117,7 +127,7 @@ ChoiceTextLine
 Choice
   = correct:ChoiceIdentifier lines:(ChoiceTextLine)+
     {
-      return {'type': 'choice', 'correct' : correct, 'text': lines.join("")};
+      return {'type': 'choice', 'correct' : correct, 'text': lines.join("").replace(/[\n\r]$/,"")};
     }
 
 MultipleChoice
@@ -156,12 +166,6 @@ Text
       return chars.join("");
     }
 
-_AndLines
-  = (' ' / '\n' / '\t')*
-
-_
-  = (' ' / '\t')*
-
 Linebreak
   = ('\n')
 
@@ -308,13 +312,13 @@ NumericalToleranceValueType
   = decimal / percentage / integer
 
 NumericalTolerance
-  = '+-' _ value:NumericalToleranceValueType _
+  = '+-' ' '* value:NumericalToleranceValueType ' '*
     {
       return value;
     }
 
 NumericalResponse
-  = CorrectAnswerIdentifier _ '(' _ value:NumericalValue _ tolerance:NumericalTolerance? ')' _ Linebreak
+  = CorrectAnswerIdentifier ' '* '(' ' '* value:NumericalValue ' '* tolerance:NumericalTolerance? ')' ' '* Linebreak
     {
       if (tolerance == "")
         tolerance = "5%"
@@ -323,6 +327,7 @@ NumericalResponse
 
 NumericalValue
   = additive
+  / VariableName
 
 /* Mathematical rules */
 

common/lib/xmodule/xmodule/js/src/capa/edit.coffee

@@ -68,6 +68,10 @@ class @CapaDescriptor
             el.children().last().remove()
             return el
 
+        variable_name_wrapper = (expression) ->
+            match = /^\{(.+)\}$/.exec(expression)
+            return if match then "$" + match[1] else expression
+
         for section in parsed
             if section.type == 'text'
                 newel = create_text_element(section.text)
@@ -116,7 +120,7 @@ class @CapaDescriptor
 
             else if section.type == 'numerical'
                 newel = $(doc.createElement('numericalresponse'))
-                newel.attr 'answer', section.answer
+                newel.attr 'answer', variable_name_wrapper(section.answer)
 
                 tolerance = $(doc.createElement('responseparam'))
                 tolerance.attr 'type', 'tolerance'
@@ -131,7 +135,7 @@ class @CapaDescriptor
 
             else if section.type == 'string'
                 newel = $(doc.createElement('stringresponse'))
-                newel.attr 'answer', section.answer
+                newel.attr 'answer', variable_name_wrapper(section.answer)
 
                 newel.append doc.createElement('textline') 
                 problem.append(newel)
@@ -139,7 +143,7 @@ class @CapaDescriptor
             else if section.type == 'formula'
                 formularesponse = $(doc.createElement("formularesponse"))
                 formularesponse.attr 'samples', section.samples
-                formularesponse.attr 'answer', section.answer
+                formularesponse.attr 'answer', variable_name_wrapper(section.answer)
                 formularesponse.attr 'type', 'cs'
 
                 tolerance = $(doc.createElement('responseparam'))