CQM.js

// env.js
_documentSetter: function(document){
  this.document = document;
  // if this is a document model it will have the watch function,
  // if not it will throw an error and everything dies, but I doubt
  // a non doc-model will be passed
  if (this._constrainedProductsWatch) {
    this._constrainedProductsWatch.remove();
  }
  
  this._constrainedProductsWatch = this.document.watch('constrainedProducts', lang.hitch(this, function(name, oldValue, newValue){
    if (newValue.length) {
      topic.publish('showCQM');
    }
  }));
}

/// builder.js
topic.subscribe('constrainedProducts', lang.hitch(this, function(){
  if (this._constrainedProductsTimeout) {
    clearTimeout(this._constrainedProductsTimeout);
  }
  
  this._constrainedProductsTimeout = setTimeout(lang.hitch(this, function(){
    this._constrainedProductsTimeout = null;
    this.CQM.show();
  }), 300);
}));

/// models/document/PageItem.js
 _atsInfoSetter: function(atsInfo){
  this.atsInfo = atsInfo;

  if (atsInfo.availableQuantity < this.quantity) {
    // something like this
    topic.publish('tooMuchQty', this.stockItem);
  }
},