Understanding Jenkins Groovy scripted pipeline code-CodePudding

I am looking at a Jenkins Scripted Pipeline tutorial here https://www.jenkins.io/blog/2019/12/02/matrix-building-with-scripted-pipeline/ and found that I need to learn some Groovy to understand this.

I have been reading through Groovy documentation, but still and not understanding all of this code. I will list the areas of question.

1

List getMatrixAxes(Map matrix_axes) {
List axes = []
matrix_axes.each { axis, values ->
    List axisList = []
    values.each { value ->
        axisList << [(axis): value]
    }
    axes << axisList
}
// calculate cartesian product
axes.combinations()*.sum()
}

In most of the Groovy documentation I have seen, it defines lists such as List axes = []. The syntax above looks more like a function which would return a List. If this is what this is, I don't see any return statement inside the curly brackets, which just confuses me.

2

node(nodeLabel) {
            withEnv(axisEnv) {
                stage("Build") {
                    echo nodeLabel
                    sh 'echo Do Build for ${PLATFORM} - ${BROWSER}'
                }
                stage("Test") {
                    echo nodeLabel
                    sh 'echo Do Build for ${PLATFORM} - ${BROWSER}'
                }
            }
        }

I have seen this concept of node in Groovy scripts before, somethings with the parameter section, ie: node(nodelabel) {...} and sometimes without, ie: node {...}. Is this core Groovy or somehow something specific to Jenkins? What does it mean and where can I find documentation about it?

CodePudding user response：

getMatrixAxes is a function. In Groovy return statement is optional. If you don't explicitly return something in a function, the last expression evaluated in the body of a method or a closure is returned. In your case, the output generated by the axes.combinations()*.sum() will be returned. In the example, it's generating a List. You can read more from here.
These constructs are something specific to Jenkins. Specifically the mentioned syntax is from Jenkins Scripted Pipeline Syntax. node {...} Simply means run on any agent. node(nodelabel) {...} means run on the agent with the label nodelabel. Jenkins has a new Job DSL called Declarative syntax which is preferred over Scripted Syntax. You can read more about both here.