Skip to content

Overloading Steps

Function Overloading1 is when there are multiple methods with the same name and different implementation.

Conflicting Library Steps

To allow multiple libraries to contribute the same step, the Pipeline Configuration must have jte.permissive_initialization set to true.

If multiple libraries do contribute the same step, the step will no longer be able to be invoked by its short_name. Instead, overloaded steps must be accessed using the Pipeline Primitive Namespace.

Overloaded Library Steps

The following example assumes a gradle and npm library are available that both contribute a build() step.

pipeline_config.groovy
jte{
  permissive_initialization = true // pipeline will fail if not set
}
libraries{
  npm    // contributes build()
  gradle // contributes build()
}
Jenkinsfile
// build() <-- would fail because step is overloaded
jte.libraries.npm.build() 
jte.libraries.gradle.build()

Default Mode is to Fail

By default, if two libraries are loaded that contribute the same step then the Pipeline Run will fail during Pipeline Initialization.

This behavior is modified by setting jte.permissive_initialization to True.

Library Steps Overriding Jenkins Pipeline Steps

Jenkins Pipeline DSL steps can be overridden by Library Steps.

If a Library Step has the same name as a Jenkins Pipeline DSL step, such as node or build, the Library Step will take precedence.

To invoke the original Jenkins Pipeline DSL Step, use the steps Global Variable.

Declarative Syntax

This isn't true for Declarative Syntax. Check out the Declarative Syntax page to learn more.

Use Case: Overriding node

If a library were to contribute a Library Step called node, then it would override the node step used in Jenkins Scripted Pipelines.

The following example shows how to override the default node step to augment its functionality.

node.groovy
// support the original node interface
void call(String label = null, Closure body){
    if(label){
      steps.node(label, body) // steps var used to access original "node" implementation
    } else {
      steps.node(body)
    }
}

// support new functionality
void call(Map args = [:], Closure body){
  if(args.containsKey("container")){
    docker.image(args.container).inside(body)
  }
}
Jenkinsfile
// assume the Pipeline Configuration loaded the library contributing node.groovy
node{ println "hi" }
node("my-label"){ println "hi" }
node(container: "maven"){ sh "mvn -v" } // custom functionality

  1. Function Overloading ↩

Back to top