Liferay edit mode: content disappears when moving portlet in another position

[mcollovati]

While editing a Liferay Content Page, when a Vaadin portlet is moved from a position to another its content is no more visible.
The issue seems to happen mainly when moving widgets inside layout containers.

To reproduce this bug:

• Build adressbook-portlet example and deploy it to the Liferay by copying in to {liferay_home}/deploy folder.
• Open localhost:8080 and login into Liferay
• Click on the "Edit" icon to start edit the page
• Open "Fragments and Widgets" panel on the right side of the page, go to "Widget" tab
• Find "Vaadin Sample" category on the botton and then "ContactList" element
• Drag and drop the widget to the page.
• Click on the "Publish" button to exit from editing mode to browse mode and click "Edit" icon again (this is needed until Vaadin Portlet content is blank in Liferay 7 page editing mode #202 is fixed).
• Drag and drop the widget in another position, for example over the "Welcome to Liferay" text
• Check that the portlet/widget is blank

Expected behavior: Portlet content is rendered
Actual behavior: Portlet content is not rendered

Versions:
Vaadin Portlet version - 1.0.0.beta4
Flow version - 2.7.8
Liferay version - 7.4
Java version - 11

[mcollovati]

At a first glance, it seems like that the problem is that when moving the portlet, a new web-component with a different id is created on the client side and a new server-side Java view component is instantiated. However, in VaadinPortlet.initComponent an already existing PortletViewContext is found, but with a reference to the previous java component instance.

Since the PortletViewContext is found, onPortletViewContextInit is not invoked on the new component, so, if the component tree is built on that method, the result on the client side will be an empty element.

A quick and dirty fix may be to check if context view is the same as the component that is being initialized, and if not create and set a new PortletViewContext, but perhaps it may be worth to do some further investigation.

// if (context == null) { // Actual code
if (context == null || context.getView() != component) { // Fix
    needViewInit = true;
    context = new PortletViewContext(component, portlet.isPortlet3,
            request.getPortletMode(), request.getWindowState());
    portlet.setViewContext(session, namespace, windowName, context);
}