Jenkins "unable to resolve class Declarative" error when building Python script-CodePudding

I began learning to use to Jenkins and wanted to make it run a Python script of mine automatically. I followed their tutorial and created a new Project called Pipeline Test.

I've also added the GitHub repo of a Python script I wanted to test (https://github.com/mateasmario/spam-bot).

As you can see, I've created a Jenkinsfile in that repo. Because my script is called spam-bot.py, I want my Jenkinsfile to run that script every time I click "Build now" inside Jenkins. This is the content of my Jenkinsfile:

Jenkinsfile (Declarative Pipeline)
pipeline {
    agent { docker { image 'python:3.10.1-alpine' } }
    stages {
        stage('build') {
            steps {
                sh 'python spam-bot.py'
            }
        }
    }
}

The problem is, whenever I click "Build now", my build fails and the console outputs the following error:

Started by user Mario Mateas
Obtained Jenkinsfile from git https://github.com/mateasmario/spam-bot.git
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 1: unable to resolve class Declarative 
 @ line 1, column 26.
   Jenkinsfile (Declarative Pipeline)
                            ^

1 error

    at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:310)
    at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:958)
    at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:605)
    at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:554)
    at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:298)
    at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:268)
    at groovy.lang.GroovyShell.parseClass(GroovyShell.java:688)
    at groovy.lang.GroovyShell.parse(GroovyShell.java:700)
    at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell.doParse(CpsGroovyShell.java:142)
    at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell.reparse(CpsGroovyShell.java:127)
    at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.parseScript(CpsFlowExecution.java:571)
    at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.start(CpsFlowExecution.java:523)
    at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:334)
    at hudson.model.ResourceController.execute(ResourceController.java:99)
    at hudson.model.Executor.run(Executor.java:432)
Finished: FAILURE

I looked up for this error on the internet, but didn't find any useful information, and that's why I decided to ask here. I also don't have any Docker container configured. Do I need to configure one? I took a look over Jenkins' documentation for Docker, but didn't see any useful information for adding a Python image (as the one mentioned at the beginning of the Jenkinsfile) to the container.

CodePudding user response：

Your Jenkinsfile contains invalid syntax on the first line, which is why the error is being thrown. Assuming you intended that first line to be a comment, you can modify the pipeline code to be:

// Jenkinsfile (Declarative Pipeline)
pipeline {
  ...
}

and your pipeline code will have valid syntax.