Uiprogress runtime error during "nats bench" when the number of publishers exceeds the number of messages

[giacomoquinalia]

Observed behavior

Running a command like nats bench foo.bar --pub 2 --msgs 1 I receive the output:

10:51:24 Starting Core NATS pub/sub benchmark [subject=foo.bar, multisubject=false, multisubjectmax=100000, msgs=1, msgsize=128 B, pubs=2, subs=0, pubsleep=0s, subsleep=0s]
10:51:24 Starting publisher, publishing 1 messages
10:51:24 Starting publisher, publishing 0 messages
panic: runtime error: index out of range [0] with length 0

goroutine 39 [running]:
github.com/gosuri/uiprogress.(*Bar).Bytes(0xc000254000)
    /home/giacomo/go/pkg/mod/github.com/gosuri/uiprogress@v0.0.1/bar.go:195 +0x40b
github.com/gosuri/uiprogress.(*Bar).String(...)
    /home/giacomo/go/pkg/mod/github.com/gosuri/uiprogress@v0.0.1/bar.go:214
github.com/gosuri/uiprogress.(*Progress).print(0xc0000a2480)
    /home/giacomo/go/pkg/mod/github.com/gosuri/uiprogress@v0.0.1/progress.go:127 +0x8f
github.com/gosuri/uiprogress.(*Progress).Listen(0xc0000a2480)
    /home/giacomo/go/pkg/mod/github.com/gosuri/uiprogress@v0.0.1/progress.go:116 +0xb3
created by github.com/gosuri/uiprogress.(*Progress).Start in goroutine 1
    /home/giacomo/go/pkg/mod/github.com/gosuri/uiprogress@v0.0.1/progress.go:134 +0x4f

Expected behavior

To prevent a runtime error when the number of messages for a publisher is zero, the progress bar could be shown as already completed instead of attempting to update it. A possible solution:

File: https://github.com/nats-io/natscli/blob/main/cli/bench_command.go#L1718

    if c.progressBar {
        barCount := numMsg
        if barCount == 0 {
            barCount = 1
        }

        progress = uiprogress.AddBar(barCount).AppendCompleted().PrependElapsed()
        progress.Width = progressWidth()

        if numMsg == 0 {
            progress.PrependFunc(func(b *uiprogress.Bar) string {
                return "Finished  "
            })
            progress.Incr()
        }
    }

    if numMsg == 0 {
        donewg.Done()
        errChan <- nil
        return
    }

Server and client version

NATS server: 2.10.20 CLI client: v0.1.5

Host environment

No response

Steps to reproduce

No response

[ripienaar]

Thanks @giacomoquinalia, feel like sending a PR with that in?

[giacomoquinalia]

Sure, here it is: https://github.com/nats-io/natscli/pull/1138