Title says it all

Jenkins Declarative Pipeline things I've learned the hard way

// This was failing my build:
   archiveArtifacts artifacts: '**/${env.DOCKER_FILE_NAME}', fingerprint: false
   // SHOULD BE THIS
   archiveArtifacts artifacts: "**/${env.DOCKER_FILE_NAME}", fingerprint: false
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// If you need vars that are global and changeable, you need them outside of the pipeline
   VAR="value"
   pipeline {
     ...
   }
   
// Env vars are only changeable temporarily with a "with env" block
pipeline {
  environment {
     VAR="VALUE"
  }
  stage {
    steps {
      VAR = "NEW VALUE"  // won't work
      withEnv(['VAR="NEW NEW VALUE"']){
        ...   // VAR will only be "NEW NEW VALUE" in this block. That's it. 
              // Not helpful for setting a global to be used later
      }
    }
  }
}    
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// I couldn't find another way to set variables in a script{} block
   // DIDN'T WORK
   EMAIL_TEXT = "Build is BACK TO NORMAL"
   // worked (╯°□°）╯︵ ┻━┻)
   EMAIL_TEXT = sh([script: "echo 'Build is BACK TO NORMAL'", returnStdout: true]).trim()
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// Declarative pipelines hate if else statements that expand vars.
    // didn't work
    if ("${CURRENT_BUILD}" == "UNSTABLE"){...}
  
    // didn't work
    if (${CURRENT_BUILD} == "UNSTABLE"){...}
     --> java.lang.NoSuchMethodError: No such DSL method '$' found among steps
    
    // didn't work
    if (CURRENT_BUILD == "UNSTABLE"){...}
    
    // didn't work
    if (CURRENT_BUILD == 'UNSTABLE'){...}

    // didn't work
    if ("${CURRENT_BUILD}" == "UNSTABLE")
      ...

    // worked (╯°□°）╯︵ ┻━┻)
    if (true) {...}
    
 // I added all my logic into a shell script and put the variables as params
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// Post build stuff doesn't like having it's own environment
post {
    environment {
        TESTS_PASSED = -1      // This failed my build and threw an exception
        TESTS_FAILED = -1
        TESTS_SKIPPED = -1
        TESTS_TOTAL = -1
    }
}