These "security" fixes start driving me crazy.

There seems to be no way to preserve the state across Jenkins restarts anymore in my library.

None of the classical Java singleton patterns (that relies on static fields) work because CPS does not serialize static fields.

`@Singleton` annotation doesn't work because AST transformation will define a `getInstance()` method without `@NonCPS` annotation making this singleton unusable from my `@NonCPS` annotated code.

Now this - I can't preserve state as a global var `@Field` anymore.

Really starting to feel like the whole objective here is to make user's life harder...

I just had a brilliant idea to implement InvisibleAction in my library and use it to store state... and what do you think? Yeah that's right - they took care of that too!

https://www.jenkins.io/blog/2018/03/15/jep-200-lts/

Well done Jenkins! Well done.

I'm feeling like Alice falling down the rabbit hole. I've tried to (for the sake of testing) executing this:

def f = ExtensionList.lookup(jenkins.security.CustomClassFilter.Static.class)[0]
f.overrides.put('my.JenkinsfileContext', true)

Which is an equivalent of `-Dhudson.remoting.ClassFilter=my.JenkinsfileContext` so I don't have to restart my Jenkins for testing.
And then I had this in my library:

@NonCPS
def diag() {
    echo "isBlacklisted(String) = ${hudson.remoting.ClassFilter.DEFAULT.isBlacklisted('my.JenkinsfileContext').toString()}"
    echo "isBlacklisted(Class) = ${hudson.remoting.ClassFilter.DEFAULT.isBlacklisted(my.JenkinsfileContext.class).toString()}"
}

It reports

[Pipeline] echo
isBlacklisted(String) = false
[Pipeline] echo
isBlacklisted(Class) = false

But, I still get

java.lang.UnsupportedOperationException: Refusing to marshal my.JenkinsfileContext for security reasons; see https://jenkins.io/redirect/class-filter/

I am looking at https://github.com/jenkinsci/jenkins/blob/jenkins-2.289.2/core/src/main/java/hudson/util/XStream2.java#L561 and I can clearly see

return ClassFilter.DEFAULT.isBlacklisted(name) || ClassFilter.DEFAULT.isBlacklisted(type);

How in the world my `my.JenkinsfileContext ` is still end up in this `BlacklistedTypesConverter`??? How many more circles of Hell I'' have to go through for such a simple basic thing as preserving my groovy lib state between the Jenkins restarts?

I am raising priority of this ticket. This does NOT conform to the "Minor". This is fundamental basic functionality that is broken.

jglick, oleg_nenashev, abayer, dnusbaum - tagging as participants on both SECURITY-1336 and JEP-200.

We need a way to preserve groovy lib state across Jenkins restarts within the same pipeline run. One way or another - this is basic requirement. The whole CPS survivability makes no sense if my groovy lib is inoperable after a restart. From my perspective fixing the `@Field` annotation sounds like the right thing to do. But if the proper way to preserve state is through InvisibleAction - we need to be able to implement action in the the lib, which I'm not sure even feasible - it won't be on the class path outside of the `WorkflowRun` (probably that's why `BlacklistedTypesConverter` still caught me above). Meanwhile any other ideas/workarounds are highly appreciated.

llibicpep I think you are overthinking this. Do not write a plugin. If @Field is broken in this context, just do not use it unless and until the bug is fixed. (Obviously it had never occurred to anyone to write a functional test with load + @Field.)

a way to preserve groovy lib state across Jenkins restarts within the same pipeline run

Just have the Jenkinsfile pass a Map or other stateful object to the library or load’ed script? Or just use a local variable?

jglick - that's what I am already doing. The problem is with saving it or a pointer to it. Library doesn't have access to local variables defined in the Jenkinsfile context.

Consider I have something like this

```groovy
myLib(this, 'pipeline.yaml')
```

As my Jenkinsfile. Yes, I was thinking about extending it to:

```groovy
def state = [:]
myLib(this, 'pipeline.yaml', state)
```

But this library generates a pipeline (as String) and `evaluate`s it. I tried to evaluate it with a custom GroovyShell and passing a Binding inside - CPS is not happy about that. Otherwise - my dynamic Jenkinsfile has no access to that state object. When other steps being called from that dynamic Jenkinsfile - they don't have access to that either. I was trying to solve it with Singleton and it works - up until Controller restarts. `@Field` doesn't work at all.

Even if I didn't had the dynamic Jenkinsfile generation - I would then had to recursively pass `state` object to every step and method in my library, which is an inconvenience at the very least.

recursively pass state object to every step and method in my library

Yes do this.