Iterate FileWrapper, fails with shell script within the loop

[Sverre Moe]

Problem looping through the result of findFiles.

The result from this method returns a org.jenkinsci.plugins.pipeline.utility.steps.fs.FileWrapper

node {
    stage("Publish") {        
        def files = findFiles(glob: '**/*.rpm')

        for (def file : files) {
            sh "echo Hello World! ${file.path}"
        }
}

Fails with java.io.NotSerializableException: java.util.AbstractList$Itr

Trying to use @NonCPS

node {
    stage("Publish") {
        def files = findFiles(glob: '**/*.rpm')
        loopFiles(files)
    }
}

@NonCPS
void loopFiles(files) {
    for (def file : files) {
        sh "echo Hello World! ${file.path}"
    }
}

It breaks the loop after first item in list. If 3 files found, then there is only one output.

However, if I remove the shell script and just use println it loops through all 3 files found.

Works if I loop the files first and put the file path in a new list:

node {
    stage("Publish") {
        def files = findFiles(glob: '**/*.rpm')
        def packages = []
        for (def file : files) {
            packages.add(file.path)
        }

        for (def packagePath : packages) {
            sh "echo Hello World! ${packagePath}"
        }
}

I reckon that FileWrapper is not serializable, hence the problem, but why doesn't the @NonCPS work on all items?

[Björn Pedersen]

See https://github.com/jenkinsci/pipeline-examples/blob/master/docs/BEST_PRACTICES.md#groovy-gotchas

[Björn Pedersen]

And of course in methods marked  as NonCPS, you can not use jenkins steps (e.g. sh).

Björn

[Sverre Moe]

Was aware of it. Iterating for loops using for(def foo : foos) will work for List. Using closure forEach does not work in Pipeline without using @NonCPS.

• Beware for (Foo f: foos) loops and Groovy closure-style operators like .each and the like. They will not work right in normal Pipeline script contexts where Pipeline steps are involved directly.

I have been using shell script within for (String f: foos) 

for (def file : files) {
  sh "scp $file user@$server:$path"
}

This works fine. No problem at all. However this time I had problem iterating through a list of FileWrapper, regardless of existing shell script within or just a simple println of it. 

Thus, putting the iteration of FileWrapper within a method annotated with @NonCPS should fix that serializable problem.

However I was unaware the sh step could not be executed within a method annotated with @NonCPS. If that is mentioned in the documentation I must have missed it.

In any case, I have a workaround with first iterating the list of FileWrapper and putting it in a new list of Strings.