GWT Module com.vaadin.v7.Vaadin7WidgetSet not found

Question

I have converted my existing project from vaadin 7 to vaadin 8 successfully. There is no error in the project, but when I use mvn install to build the project. I am getting this error:- GWT Module com.vaadin.v7.Vaadin7WidgetSet not found in project sources or resources.

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 02:51 min
[INFO] Finished at: 2017-12-19T12:31:15+05:30
[INFO] Final Memory: 94M/1007M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.vaadin:vaadin-maven-plugin:8.0.6:compile (default) on project XXX: GWT Module com.vaadin.v7.Vaadin7WidgetSet not found in project sources or resources. -> [Help 1]

Answer 1

From here:

Check the following:

You have to replace the vaadin-server dependency with vaadin-compatibility-server.

If you are using the default widgetset (you are not compiling it by yourself):

Replace the vaadin-client-compiled dependency with vaadin-compatibility-client-compiled.

Add @Widgetset("com.vaadin.v7.Vaadin7WidgetSet") to your UI implementations.

If you are using a custom widgetset:

Replace the vaadin-client dependency with vaadin-compatibility-client.

Recompile it.

In your POM I see these lines:

    <dependency>
        <groupId>com.vaadin</groupId>
        <artifactId>vaadin-server</artifactId>
        <version>7.5.10</version>
    </dependency>

    <dependency>
        <groupId>com.vaadin</groupId>
        <artifactId>vaadin-themes</artifactId>
        <version>7.5.10</version>
    </dependency>
    <dependency>
        <groupId>com.vaadin</groupId>
        <artifactId>vaadin-client-compiled</artifactId>
        <version>7.5.10</version>
    </dependency>

    <dependency>
        <groupId>com.vaadin</groupId>
        <artifactId>vaadin-client</artifactId>
        <version>7.5.10</version>
        <exclusions>
            <exclusion>
                <groupId>javax.validation</groupId>
                <artifactId>validation-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

This won't work, you can't include any version 7 components, servers, clients. The only valid thing, is to use the v8-compatibility things.