logstash-plugin preventing colored output from ansicolor

[tszmytka]

I have the same issue but i have found why we have the issue.

Jenkins: 2.263.4
AnsiColor: 0.7.5

To confirm our issue, while the job is running, the output is correct all the way up to completion. When we refresh the page or revisit it, the problem occurs. I have found a fixed (in our use case) and can replicate:

This pipeline job works fine including after refresh:

ansiColor('xterm') {
    node {
        stage('test') { // for display purposes
            sh 'printf "\\e[31mHello World\\e[0m\\n"'
            sh 'printf "Normal \\e[1mBold\\e[0m\\n"'
            sh 'printf "Normal \\e[4mUnderlined\\e[0m\\n"'
        }
    }
}

But we use the logstash plugin to output the logs to ES so the actual setup we use is this:

logstash {
    ansiColor('xterm') {
        node {
            stage('test') { // for display purposes
                sh 'printf "\\e[31mHello World\\e[0m\\n"'
                sh 'printf "Normal \\e[1mBold\\e[0m\\n"'
                sh 'printf "Normal \\e[4mUnderlined\\e[0m\\n"'
                
                sleep 5
            }
        }
    }
}

The output is fine during the run (had to put a sleep in to see the job showed correctly during the run) but after refreshing i get the issue:

If i switch around the logstash and ansi classes it works fine:

ansiColor('xterm') {
    logstash {
        node {
            stage('test') { // for display purposes
                sh 'printf "\\e[31mHello World\\e[0m\\n"'
                sh 'printf "Normal \\e[1mBold\\e[0m\\n"'
                sh 'printf "Normal \\e[4mUnderlined\\e[0m\\n"'
                
                sleep 5
            }
        }
    }
}

Originally posted by @thenom in #216 (comment)

[tszmytka]

Similar to #193 and #201

[tszmytka]

@thenom Thank you for identifying the issue.
As mentioned earlier - this is not really a bug in ansicolor-plugin but rather in logstash-plugin - if used around other steps it doesn't transfer metadata for some of the log lines which coloring functionality relies on.
Nevertheless I've prepared a workaround that forces correct behavior at a small cost of 2 additional empty lines in the log output.