Jenkins - get list of parameters from internal memory

vars_lib.groovy

static def getBuildParameters(currentBuild) {
    def project = currentBuild.getRawBuild().getParent()
    def params = null

    // Find or create parameters object
    for (e in project.properties) {
        if (e.value instanceof ParametersDefinitionProperty) {
            params = e.value
            break
        }
    }

    // If there wasn't one, create and set so we have something to return
    if (! params) {
        params = new ParametersDefinitionProperty([])
        project.addProperty(params)
    }

    return params.parameterDefinitions
}