I'm trying to write a common library building Docker images from Dockerfile. I wrote a reusable global pipeline, where I'm iterating over Dockerfile lines. I tried to use Java 8 Streams, however I ended up with issue potentially related to JENKINS-26307 and JENKINS-42769, which is not related not to Groovy functional features, but Java 8 feature.

 An example code used:

def getMissingLabels(Map<String, String> labels) {
 ['label1', 'label2', 'label3', 'label4'].stream()
        .filter({ label -> !isLabelDefined(label, labels) })
        .collect(Collectors.toList())
}

Whole stream execution results in "false" boolean result, instead of a list. Even complex streams are passing through, but evaluates to "false". When using more complex stream like:

Arrays.stream(splitted)
            .filter { it.startsWith('LABEL') }
            .map { it.replaceAll('(LABEL)|"', '') }
            .map { it.trim() }
            .map { it.split('=', 2) }
            .collect(Collectors.toMap(
            { val -> val[0].toLowerCase() },
            { val -> val[1] }))

it enters only first filter expression and does not evaluate the rest.

When replaced functional style code with typical imperative style (for loop) it works.