Closure compiler --debug solves my bug

Question

So it seems that debugging is getting a new meaning, at least in Closure Compiler.

I have a rather big code base, and isolating the problem is a difficult task. In my entry point class I instantiate the dependencies. One of these, is not created correctly, the object is there, but its constructor is not being called.

This only happens in ADVANCED mode, so I tried to pass --debug flag, and voila, the bug is gone, the constructor gets called. It's mind blowing. I can't copy paste any particular code, what would you suggest?

/**
 * @param {Element} parent
 * @param {Object}  opts
 * @constructor
 */
ns.App = function(parent, opts) {
    this.options = new ns.Options(opts || {});

    var w = this.options.width || parent.offsetWidth;
    var h = this.options.height || parent.offsetHeight;
    this.view = new ns.AppView(w, h);
    this.history = new ns.CommandManager();

    // ....

    // this one doesn't get called
    this.amx_ = new ns.ActivityManager(this, this.options);
    // this one does
    this.output_ = new ns.Writer();
    this.bind_();
};

Answer 1

With Closure-compiler, when the debug flag makes the error go away it usually indicates that you have a renaming collision. This can be caused by setting properties on an externally defined object who's properties are not completely defined to the compiler. The compiler renames your property to the same name as an existing property.

This can also be caused by referencing a property using dotted syntax (obj.prop) where it was declared using quoted syntax (obj['prop']). By definition, the compiler sees these as different properties.

Make sure you turn on --warning_level VERBOSE to help identify accessing undefined properties. Although it is still possible that your particular case won't be recognized.