stringify: do not use unescapedIndexOf in property parameters

… as \ is no escape character there.  When the propery parameter
contains :, then it must be quoted, the colon cannot be escaped.

As the function stringify.propertyValue in fact stringifies
property parameter values, it is renamed accordingly.

lib/ical/stringify.js

@@ -4,7 +4,7 @@
  * Portions Copyright (C) Philipp Kewisch */
 
 import design from "./design.js";
-import { foldline, unescapedIndexOf } from "./helpers.js";
+import { foldline } from "./helpers.js";
 
 const LINE_ENDING = '\r\n';
 const DEFAULT_VALUE_TYPE = 'unknown';
@@ -122,16 +122,15 @@ stringify.property = function(property, designSet, noFold) {
     if (multiValue && Array.isArray(value)) {
       value = value.map(function(val) {
         val = stringify._rfc6868Unescape(val);
-        val = stringify.paramPropertyValue(val, paramDesign.multiValueSeparateDQuote);
+        val = stringify.propertyParameterValue(val, paramDesign.multiValueSeparateDQuote);
         return val;
       });
       value = stringify.multiValue(value, multiValue, "unknown", null, designSet);
     } else {
       value = stringify._rfc6868Unescape(value);
-      value = stringify.paramPropertyValue(value);
+      value = stringify.propertyParameterValue(value);
     }
 
-
     line += ';' + paramName.toUpperCase() + '=' + value;
   }
 
@@ -209,16 +208,16 @@ stringify.property = function(property, designSet, noFold) {
  * If any of the above are present the result is wrapped
  * in double quotes.
  *
- * @function ICAL.stringify.paramPropertyValue
+ * @function ICAL.stringify.propertyParameterValue
  * @param {String} value      Raw property value
  * @param {boolean} force     If value should be escaped even when unnecessary
  * @return {String}           Given or escaped value when needed
  */
-stringify.paramPropertyValue = function(value, force) {
+stringify.propertyParameterValue = function(value, force) {
   if (!force &&
-      (unescapedIndexOf(value, ',') === -1) &&
-      (unescapedIndexOf(value, ':') === -1) &&
-      (unescapedIndexOf(value, ';') === -1)) {
+      (value.indexOf(',') === -1) &&
+      (value.indexOf(':') === -1) &&
+      (value.indexOf(';') === -1)) {
 
     return value;
   }

test/stringify_test.js

@@ -113,6 +113,13 @@ suite('ICAL.stringify', function() {
       delete ICAL.design.defaultSet.param.type;
     });
 
+    test('stringify property value containing "escaped" ; , :', function() {
+      let subject = new ICAL.Property('attendee');
+      subject.setParameter('cn', 'X\\:');
+      subject.setValue('mailto:id');
+      assert.equal(subject.toICALString(), 'ATTENDEE;CN="X\\:":mailto:id');
+    });
+
     test('rfc6868 roundtrip', function() {
       let subject = new ICAL.Property('attendee');
       let input = "caret ^ dquote \" newline \n end";