IntelliJ IDEA Scratch File: JSF xmlns URI not registered

Question

From the Intellij website:

Scratch Files, a very handy feature that helps you experiment and prototype. With this feature you can sketch something really quick right in the editor, without modifying your project or creating any files.

You can open an infinite number of Scratch Files and easily switch between them. IntelliJ IDEA will provide all of its coding assistance features for these files according to the type you will select for them in a status bar widget.

However, when I create a facelet scratch file the "URI is not registered" error appears, none of the tags are recognized, and tab-completion of tags as I type does not happen.

I create the new facelet scratch file as follows:

Tools -> New Scratch -> XHTML file

When the mouse hovers over one of the red-highlighted xmlns lines a balloon pops up: URI is not registered (Settings | Project Settings | Schemas and DTDs). When the mouse hovers over the h:outputLabel tag a balloon pops up: Cannot resolve symbol: 'h:outputLabel'. However, in my project there are no such errors in any of my Facelet files.

According to Jetbrains, "IntelliJ IDEA will provide all of its coding assistance features for these files according to the type you will select for them in a status bar widget." Is this just a broken feature or is there a way to resolve this problem? It's completely not useful to have a XHTML scratch file that does not provide coding assistance.

UPDATE:

Changing to java.sun.com namespace does not resolve the issue:

Answer 1

I've fixed this issue on IntelliJ. In "settings > plugins", install "Jakarta EE:Server Faces(JSF)" or enable it