wtf nth

App Engine Fails to Start with GWT

I fired up Eclipse today, and saw this error when I tried to run or debug my GWT app:

Unable to load server class 'com.google.appengine.tools.development.gwt.AppEngineLauncher'
java.lang.ClassNotFoundException: com.google.appengine.tools.development.gwt.AppEngineLauncher
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at com.google.gwt.dev.DevMode$ArgHandlerServer.setString(DevMode.java:117)
at com.google.gwt.util.tools.ArgHandlerString.handle(ArgHandlerString.java:26)
at com.google.gwt.util.tools.ToolBase.processArgs(ToolBase.java:238)
at com.google.gwt.dev.ArgProcessorBase.processArgs(ArgProcessorBase.java:29)
at com.google.gwt.dev.DevMode.main(DevMode.java:308)

(more junk omitted at the end)

I don’t know what caused it, but I was able to clone the again from Bitbucket (to the same revision) and now it works. Ugh. GWT is so finicky.