Vaadin: failed to load widgetset.nocache.js

I had the same problem 'Failed to load the widgetset: ' and it came up when I tried to run the Vernotologist demo application by fetching from svn. To solve this:

1. Goto your gwt.xml file and make sure it is selected in the project explorer in eclipse
2. Make sure your Vaadin in eclipse plugin is installed
3. Find the Compile Widgetset Button in Eclipse Toolbar which comes as part of the vaadin plugin and looks like a gear. Click it
4. Step 3 will compile the widget set for you
5. Restart server and re-run your application

Source: 16.2.2. Compiling the Widget Set from Book of Vaadin at this link: https://vaadin.com/book/-/page/gwt.eclipse.html

You need to compile your widgetset. To enable it, you need something like this in your pom:

        <!-- vaadin update widgetset step 1: need (re)build? -->
        <plugin>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-maven-plugin</artifactId>
            <version>1.0.2</version>
            <executions>
                <execution>
                    <goals>
                        <goal>update-widgetset</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

        <!-- vaadin update widgetset part 2: compile -->
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>gwt-maven-plugin</artifactId>
            <version>2.3.0-1</version>
            <configuration>
                <webappDirectory>src/main/webapp/VAADIN/widgetsets</webappDirectory>
                <extraJvmArgs>-Xmx512M -Xss1024k</extraJvmArgs>
                <runTarget>clean</runTarget>
                <hostedWebapp>${project.build.directory}/${project.build.finalName}</hostedWebapp>
                <noServer>true</noServer>
                <port>8080</port>
                <soyc>false</soyc>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>resources</goal>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

When in place, recompile your app. You should see something similar to what is described in chapter 15.5.3 following the link you provided. It takes some time to compile the widgetset, so it cannot go unnoticed.

You also need a ProjectWidgetSet.gwt.xml and a reference to it in web.xml, but since the error message you are getting already mentions ProjectWidgetSet (as opposed to DefaultWidgetset), I am guessing you already did that.