[PATCH] prevent dojo.declare stack corruption due to unhandled exceptions

[newmanb@…]

The function dojo.lang.declare.base._inherited wraps each method of a declared class in another function which keeps track of the prototype of the receiving object while calling the original method. The prototype needs to be reset to its original value after the function call, but if an unhandled exception is thrown inside the original method, the reset step will be skipped. This (usually silent) failure leads to really nasty inheritance bugs.

I propose a simple fix: wrap the method call in a try-catch block, catch and re-throw all exceptions, but include a finally clause to ensure that the prototype will be reset no matter what happens. Just another step towards making the _inherited function invisible to the client.

If dojo.declare is going to see as much use as I anticipate, this pitfall really has to be fixed. I gave it a high priority because the fix is so simple, and yet (IMHO) pretty important.

Here's the patch:

Index: src/lang/declare.js
===================================================================
--- src/lang/declare.js (revision 5211)
+++ src/lang/declare.js (working copy)
@@ -122,10 +122,11 @@
        _getPropContext: function() { return (this.___proto||this); },
        // caches ptype context and calls method on it
        _inherited: function(ptype, method, args){
-               var stack = this.___proto;
+               var result, stack = this.___proto;
                this.___proto = ptype;
-               var result = ptype[method].apply(this,(args||[]));
-               this.___proto = stack;
+               try { result = ptype[method].apply(this,(args||[])); }
+               catch (e) { throw e; }
+               finally { this.___proto = stack; }
                return result;
        },
        // invokes ctor.prototype.method, with args, in our context

[newmanb@…]

same as the diff pasted above, but perhaps easier to apply

[sjmiles]

Agree with analysis, added try/catch/finally block to dojo.declare._inherited.

[(none)]

Milestone 0.4 deleted