Extending String with dojo.extend breaks String.toString() in IE

[[email protected]…]

If you extend the built-in String class using dojo.extend, it breaks the String class in Internet Explorer by overwriting the original String.toString with Object.toString.

Example:

dojo.lang.extend(String, { mytest: function() { } });

The problem occurs in source:trunk/src/bootstrap1.js in dojo._mixin(), which has an explicit block that handles custom toString methods in IE:

// IE doesn't recognize custom toStrings in for..in
if(dojo.render.html.ie && dojo.lang.isFunction(props["toString"]) && 
   props["toString"] != obj["toString"])

Assuming the user did not add a custom toString method, the property object passed in automatically inherits a toString() method from Object. In the test above, propstoString? is the same as Object.toString() and will never match objtoString? because the String prototype overrides toString().

In my opinion, the appropriate fix is to add an additional test against Object.toString:

dojo._mixin = function(/*Object*/ obj, /*Object*/ props){
    // summary:     Adds all properties and methods of props to obj.
    var tobj = {};
    for(var x in props){
        // the "tobj" condition avoid copying properties in "props"
        // inherited from Object.prototype.  For example, if obj has a custom
        // toString() method, don't overwrite it with the toString() method
        // that props inherited from Object.protoype
        if(typeof tobj[x] == "undefined" || tobj[x] != props[x]) {
            obj[x] = props[x];
        }
    }
    // IE doesn't recognize custom toStrings in for..in
    if(dojo.render.html.ie && dojo.lang.isFunction(props["toString"]) && 
       props["toString"] != obj["toString"]) && 
       props["toString"] != tobj["toString"]) { // <-- ADDED test against tobj
        obj.toString = props.toString;
    }
    return obj;
}

[[email protected]…]

Diff against trunk at r5100

[[email protected]…]

Whoops, forget to specify this was the 0.3x series. Reproduced against trunk and the patch was against trunk at revision 5100.

[Tom Trenka]

I'll take it, will fix shortly.

[Tom Trenka]

Fixed, r5267

[(none)]

Milestone 0.4 deleted