Jenkins pipeline parameter being evaluated to previous value - jenkins

Question

I've got a pipeline which builds software, with a parameter used for the version.
The parameter defaults to a Groovy expression evaluating to the current date.
But when I run it, the value it's using is actually the date of the previous build.
Example:
Build #17 (25 Mar 2022, 10:37:57) prints 2022-03-25T10:37:51.471369100
Build #18 (25 Mar 2022, 11:08:33) prints 2022-03-25T10:37:57.857506500
Build #19 (25 Mar 2022, 11:09:52) prints Build version 2022-03-25T11:08:33.802312
Pipeline Script:
pipeline {
agent any
parameters {
string(
name: "BUILD_VERSION",
defaultValue: "Build version "+java.time.LocalDateTime.now()
)
}
stages {
stage("Print") {
steps {
echo params.BUILD_VERSION
}
}
}
}
What am I missing? How can I default the parameter to the date it's executed?

Answer 1

When you are using the the defaultValue attribute of the string parameter you are actually setting the default value for the next execution of the project, not for the current one - as the default value is updated only after the build started to run with the given parameters.
Therefore the next build will be executed with the value set by the previous one.
To overcome this you need to define a parameter that is updated before the builds starts to run, and then the build will use that parameter in the execution.
One way to do it is with the Extended Choice Parameter Plugin which will generated the default value on runtime when you click the Build With Parameters in your job. This way the default time value will be used for the current running build.
Here is the code example:
pipeline {
agent any
parameters {
extendedChoice(name: 'BUILD_VERSION', type: 'PT_TEXTBOX',
defaultGroovyScript: 'return java.time.LocalDateTime.now().toString()')
}
stages {
stage("Print") {
steps {
echo params.BUILD_VERSION
}
}
}
}