Vaadin arquetype and wildfly

I have created a maven project using vaadin-arquetype. 
I did Run as --> Maven install (to create the war package)
I deployed to the wildfly server (adding the package from local repository)

In the browser (loclahost:8080/app) i saw the ERROR:
FAILED TO LOAD WIDGETSET.

I dont know what is the problem
Someone could help me?

In the pom i found the dependency vaadin - client - compìler commented.
And the info...
<!--
          Needed when using the widgetset optimizer (custom ConnectorBundleLoaderFactory).
          For widgetset compilation, vaadin-client-compiler is automatically added on the
          compilation classpath by vaadin-maven-plugin so normally there is no need for an
          explicit dependency.
        -->
I had to commented the scope so now my POM is ...        

<dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-client-compiler</artifactId>
            <!--  scope>provided</scope-->
 </dependency>
        
Now it works but i don't know why...

Three questions:

• Why did i need the dependency vaadin-client-compiler?
• Why vaadin-maven-plugin did't add the compiler?
• Why have i comment the provided scope?

In the section Create a project with Eclipse (using eclipse maven plugin) it is said...

Before running the project for the first time, select Compile Widgetset and Theme from the menu shown in Compile Widgetset and Theme Menu.

But in create project with maven they don't mentioned it. But it's said ... 
If you use Vaadin add-ons that include a widget set or make your custom widgets, you need to enable widget set compilation in the POM.

-----------------------------------------------

In the vaadin libraries section it is said:

vaadin-client-compiler-7.x.x.jar
The Vaadin Client Compiler is a Java-to-JavaScript compiler that allows building client-side modules, such as the Client-Side Engine (widget set) required for server-side applications. The compiler is needed, for example, for compiling add-on components to the application widget set, as described in Using Vaadin Add-ons.

vaadin-client-compiled-7.x.x.jar
A pre-compiled Vaadin Client-Side Engine (widget set) that includes all the basic built-in widgets in Vaadin. This library is not needed if you compile the application widget set with the Vaadin Client Compiler.
-----------------------------------------------

So when i create a maven project with the arquetype i only use built-in widgets.
I suppose that i have to compile them.

So now i understand to enable the dependency vaadin-client-compiler in the POM .

However with the plugin you can compile the widgetset and the theme before.
That will solve the problem with the widgetset,
Why the documentation don't say anything about that in the section create the proyect with maven or in the tutorial?