I have a jenkins job using the credentials-helper and which runs perfectly fine with the underlying tool set (maven, ant).

When running the build job, ant echoproperties lists the variable twice

01:26:21 [echoproperties] #Ant properties
01:26:21 [echoproperties] #Fri Aug 31 01:26:22 CEST 2018
01:26:21 [echoproperties] env.mgr.target.user=****
01:26:21 [echoproperties] mgr.target.user=****

When switching to jenkins pipeline (declarative) the credentials binding is used the same way:

withCredentials([[$class: 'UsernamePasswordMultiBinding', credentialsId: 'my.user', 
    usernameVariable: 'mgr.target.user', 
    passwordVariable: 'mgr.target.password']]) {

But here the variable is only available as env.mgr.target.user but not as mgr.target.user

01:30:31 [echoproperties] #Ant properties
01:30:31 [echoproperties] #Fri Aug 31 01:30:32 CEST 2018
01:30:31 [echoproperties] env.mgr.target.user=****

Result is that the build job fails cause the maven/ant task running as ant does not find the property mgr.target.user

To me this seems an issue as the behavior from a Jenkins job vs. Jenkins pipeline is different.

Obviously the underling maven/ant files could be changed to use the existing variable but this is not the point as the behaviour of my jenkins job should be the same.