Jenkins: Bypass Shell Variable validation when not set

I have conditionally set Jenkins parameter to read USER_INPUT_VALUE based on upstream ${SHOW_OPTION} condition YES or NO.

if ("$SHOW_OPTION" == ("NO")) {
     properties([ //No USER INPUT passed
       ])
else
{
     properties([
       parameters([ string(name: 'USER_INPUT_VALUE', defaultValue: 'mydefault']")
     ])
}

Later Jenikinsfile calls a shell script as ONE Liner which assigns a shell variable like below, When SHOW_OPTION is NO, I am assigning the hardcoded value, else actual USER value,

if [ ${SHOW_OPTION} == "NO" ]; then TARGET='"NO_USER_VALUE"'; else TARGET=$USER_INPUT_VALUE; fi;

But when SHOW_OPTION is NO, build complains as groovy.lang.MissingPropertyException: No such property: USER_INPUT_VALUE for class: groovy.lang.Binding

Why script is validating else part here as it is not applicable. Is there any way to skip this validation in shell script.

Note: When I run one liner on regular shell I dont see any issue (verified with echo $?)

declarative pipeline

• Don't forget to start the bash script with #!/bin/bash
• Build parameters are not sent to shell script.
• Only jenkins env vars are sent to the shell script.

def scriptContent = """#!/bin/bash

echo "script arguments"
echo "$@" 

#echo "env variables passed to script"
#env 

if [ $SHOW_OPTION == "NO" ]; then TARGET=\'"NO_USER_VALUE"\'; else TARGET=$USER_INPUT_VALUE; fi;

echo "shell result:"
echo TARGET="$TARGET"
""";

pipeline {
    agent any
    
    environment {
        SHOW_OPTION="NO"
    }    
    
    stages {
        stage('Setup parameters') {
            steps {
                
                //simulating your shell script
                writeFile(file: "script.sh" , text: scriptContent) 
                
                script { 
                    if ("$SHOW_OPTION" == ("NO")) {
                         println "no parameters are configured"
                    }else{
                         properties([
                           parameters([
                                string(defaultValue: 'mydefault', name: 'USER_INPUT_VALUE')
                            ])  
                         ])
                    }
                }
                
                println "build params"
                println params
                //simulating your shell script
                sh "chmod +x script.sh"
                sh "./script.sh"
            }
        }
    }   
}

Result when SHOW_OPTION is "YES":

Result when SHOW_OPTION is "NO":

> Note: The parameter should be deleted manually because when SHOW_OPTION=YES , the parameters was added to the pipeline. Because of this, I advice to not configure dynamic parameters in the pipeline. You could add the parameter in a standard way and compare if its value is null

scripted pipeline

In case someone is using a scripted pipeline, this work as expected:

def SHOW_OPTION= "true";

node {

    if ("$SHOW_OPTION" == "NO") {
     println "no parameters"
    }else{
        properties(
            [
                parameters([
                        string(defaultValue: 'mydefault', name: 'USER_INPUT_VALUE')
                ])   
            ]
        )      
    }

    println params.USER_INPUT_VALUE
    
}