Jenkinsfile Interpolation Syntax Issue

I have the following Step in my Declarative Jenkinsfile:

stage('Download Lambda Artifacts') {
    steps {
        script {
            withCredentials([usernamePassword(credentialsId: ARTIFACTORY_CREDENTIALS_ID, usernameVariable: 'ARTIFACTORY_USERNAME', passwordVariable: 'ARTIFACTORY_PASSWORD')]) {
                def lambdaNames = env.LAMBDA_NAME.tokenize(',')
                for (lambdaName in lambdaNames) {
                    sh '''
                        python get-artifact.py -u ${ARTIFACTORY_USERNAME} -p ${ARTIFACTORY_PASSWORD} -b "${lambdaName}.jar"
                    '''
                }
            }
        }
    }
}

The python script essentially just downloads the ${lambdaName}.jar from my Artifactory, and LAMBDA_NAME is just a bunch of strings separated by a comma.

Here is my issue: "${lambdaName}.jar" is not being interpolated, and is an empty value.

If i use """ for my sh instead of ''', it works, but then I get the warning about my ARTIFACTORY_USERNAME/PASSWORD having insecure interpolation of sensitive variables.

I'm sure it's a simple syntax issue, and I though wrapping my ${lambdaName} within "" would fix the issue. Is anyone able to see an solution? Many thanks.

As you seem to already know from the question, you need to interpolate the lambdaName as a Groovy variable within the string, and resolve the credentials variables as environment variables in the shell interpreter to avoid leaking them in the pipeline logs. You can achieve this via:

sh "python get-artifact.py -u \${ARTIFACTORY_USERNAME} -p \${ARTIFACTORY_PASSWORD} -b ${lambdaName}.jar"

Escaping the $ characters prevents Groovy from interpolating them within the string, and will instead cause them to be resolved by the shell interpreter. The " syntax interpolates the lambdaName as per usual within the Groovy string as you expect.