What version have you used before?

The temporary "workaround" is to remove configuration filters from project configurations. Then the Groovy script evaluation will be skipped.

BTW, evaluation failures should not break the jobs loading...

I don't know which version exactly was running before, sorry.

The workaround works (somewhat) – I manually edited the config.xml file and commented out the <combinationFilter> line, which makes the project appear again after a jenkins restart or "reload config from disk".

However, the filter was there intentionally of course, i.e. we need to filter there otherwise other things would break, so a permanent fix for this would be very welcome.

Could you share the failing script?

I'm getting the same error. I didn't lose all my jobs. Can't parse out why I lost the ones I did and kept others. But heres the log output

Failed Loading job Api_Trunk
groovy.lang.MissingPropertyException: No such property: hudson for class: Script1
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:50)
at org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:49)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGroovyObjectGetProperty(AbstractCallSite.java:231)
at Script1.run(Script1.groovy:1)
at hudson.matrix.FilterScript.evaluate(FilterScript.java:36)
at hudson.matrix.FilterScript.apply(FilterScript.java:73)
at hudson.matrix.Combination.evalGroovyExpression(Combination.java:101)
at hudson.matrix.Combination.evalGroovyExpression(Combination.java:91)
at hudson.matrix.MatrixProject.rebuildConfigurations(MatrixProject.java:623)
at hudson.matrix.MatrixProject.onLoad(MatrixProject.java:490)
at hudson.model.Items.load(Items.java:273)
at jenkins.model.Jenkins$18.run(Jenkins.java:2593)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:904)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

zgallagher: Your script is likely referencing a class that's not available in the new Matrix Project plugin's class loader by it's fully qualified name (e.g. hudson.model.Hudson). But it'd be best if you would share your script(s) – or a simplified variant that also shows the problem – to facilitate further analysis.

I've tried with a Groovy script (in Combination Filter) that contains only "true" (the simplest possible expression). Same error and stacktrace.