With SharePoint Framework (SPFx) Extensions, you can now customize more facets of the SharePoint experience, including standard page elements like headers as well as command sets and list rendering. Since the launch of the first preview of SPFx Extensions in June, we’ve been looking at feedback and scenarios from developers and adjusting the release. We are pleased to announce a Release Candidate 0 (RC0) which includes some updates to SPFx APIs for Extensions as well as a number of fixes and improvements. View the latest release notes, try the latest SPFx extensions tutorials, and install the latest SharePoint Framework Extensions tooling updates to get your code ready for upcoming general availability.
One of the most significant changes in RC0 comes for Application Customizers. In modern client web apps such as SharePoint, the page lifecycle has a variety of different entry points and updates that can happen – pages get opened, in-page navigations happen, parts are added and removed, and so on. Based on these changes, the availability of placeholders can change, and SharePoint Framework Extensions need to be flexible for that. For these reasons, we have shifted the Application Customizer extensions model to an event driven model in RC0 and away from the render() method. In RC0, you will need to attach to events such as this.context.placeholderProvider.changed (typically in your onInit methods) to customize placeholder elements as they are added. We have also updated the placeholders from "header" and "footer" nomenclature over to "top" and "bottom" placeholders.
With the RC0 release and over the next day, SharePoint Framework Extensions will also be made available in First Release tenancies so you can try Extensions across a broader set of scenarios.
Finally, the RC0 release also brings many improvements and fixes to SharePoint Framework, including for web part scenarios: we’ve now moved SPFx tooling to include TypeScript 2.4, new packaging flexibility allows multiple web parts and common code in one bundle, new improvements to the Dialog APIs, and more.
There are many different scenarios for customizing SharePoint pages, lists, and sites for which SharePoint Framework Extensions provides the foundation. With the release of RC, now is the best time to evaluate SharePoint Framework Extensions in your sites and applications and for your scenarios. We look forward to your feedback at the SharePoint Developer TechCommunity and on GitHub.