Understanding Promise deprecation warnings in ArcGIS API for JavaScript?

Question

I am trying to update legacy map code to the latest ArcGIS version of 4.6 and noticed this warning in the console when querying a feature layer. [esri.core.Promise] DEPRECATED: then() -- use .when(callback, errback) instead So I tried to change then to when, but got when is not a function errors. I also tried running the sample code from the site and got the same errors. view.whenLayerView(featureLayer).then(function(lyrView) { lyrView.watch("updating", function(val) { if (!val) { // wait for the layer view to finish updating // query all the features available for drawing. lyrView.queryFeatures().then(function(results) { graphics = results; var fragment = document.createDocumentFragment(); results.forEach(function(result, index) { var attributes = result.attributes; var name = attributes.ZIP + " (" + attributes.PO_NAME + ")" // Create a list zip codes in NY var li = document.createElement("li"); li.classList.add("panel-result"); li.tabIndex = 0; li.setAttribute("data-result-id", index); li.textContent = name; fragment.appendChild(li); }); // Empty the current list listNode.innerHTML = ""; listNode.appendChild(fragment); }); } }); });I also tried setting the "esri-promise-compatibility" flag to 1 but that didn't help. Can't see anything in the docs or community forums about this. Anyone come across this before?

RodrigoFelga · Answer

You need to replace then for when just when a class resolve to a promise. I don't see in you code any point to change, maybe the warning came from inside the api. Also happend to me to see warnings that came from inside the api and I can't resolve. Like view.then(function(){});‍‍‍ To view.when(function(){});‍‍‍ When a method resolve to a promise you don't need to change. Read more here: Making Better Promises | ArcGIS Blog Here is a list of classes that have a then method: Overview | API Reference | ArcGIS API for JavaScript 4.6