Use withCredentials([usernamePassword( ... ) ]) in Jenkins Pipeline Library - jenkins

Question

I'm trying to move some functions from a Jenkins Pipeline to a shared jenkins library. But I get errors when using the Credentials Binding Plugin (withCredentials)
For example I have this block of code:
withCredentials([usernamePassword(credentialsId: 'foobar', usernameVariable: 'fooUser', passwordVariable: 'fooPassword')]) {
// do something with credentials
}
When I move this block to a static library function I get the following error:
hudson.remoting.ProxyException:
groovy.lang.MissingMethodException:
No signature of method: static mylib.MyClass.usernamePassword() is applicable for argument types:
(java.util.LinkedHashMap) values: [[credentialsId:foobar, usernameVariable:fooUser, ...]]
Library Code:
package mylib;
class MyClass {
def static String doSomething() {
withCredentials([usernamePassword(credentialsId: 'foobar', usernameVariable: 'fooUser', passwordVariable: 'fooPassword')]) {
// some code
}
}
}
Usage in Jenkins Pipeline:
#Library('my-pipeline-library')
import mypackage.MyClass
...
MyClass.doSomething();
How can I use withCredentials/usernamePassword in my Jenkins Library? Do I need to qualify the functions with some package? Do I need extra imports? Is there any documentation about this?

Answer 1

I found a possible solution, not sure if i really like it:
I can pass the current script (this) from the pipeline script to the library. Then I can use this script variable to use functions in my pipeline library.
Looks like this:
Library Code:
package mylib;
class MyClass {
def static String doSomething(script) {
script.withCredentials([script.usernamePassword(credentialsId: 'foobar', usernameVariable: 'fooUser', passwordVariable: 'fooPassword')]) {
// some code
}
}
}
Usage in Jenkins Pipeline:
#Library('my-pipeline-library')
import mypackage.MyClass
...
MyClass.doSomething(this);

Answer 2

Myabe not the best method, but you can use the credential in the pipeline and pass what you extract from it as a parameter to the class:
jenkinsfile:
import com.mydomain.gcp
Gcp gcp = new Gcp()
Pipeline{
environment {
gcpCredentialId = 'YOUR-CREDENTIAL-ID'
}
stages {
stage('Authenticate') {
steps {
script {
withCredentials([file(credentialsId: env.gcpCredentialId, variable: 'gcpAuthFile')]) {
gcp.authenticate("${gcpAuthFile}")
}
}
}
}
}
}
then in the src\com\mydomain\Gcp.groovy file:
package com.mydomain.gcp
def authenticate(final String keyFile) {
sh "gcloud auth activate-service-account --key-file=${keyFile}"
}
return this