Cannot get ProxyWriter to show bytes written

[AlexThurston]

When using the ProxyWriter, it doesn't seem as though CurrentKibiByte is being displayed or updated correctly.

Using the following example:

package main

import (
	"fmt"
	"io"
	"net/http"

	"github.com/vbauerster/mpb/v8"
	"github.com/vbauerster/mpb/v8/decor"
)

func main() {
	url := "https://httpbin.org/drip?duration=10&numbytes=20&delay=0&code=200"
	resp, err := http.Get(url)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		panic(fmt.Sprintf("bad status code: %d", resp.StatusCode))
	}

	p := mpb.New(mpb.WithWidth(4))
	bar := p.New(-1,
		mpb.NopStyle(),
		mpb.PrependDecorators(decor.CurrentKibiByte("% .2f")),
		mpb.AppendDecorators(decor.Elapsed(decor.ET_STYLE_GO)),
	)

	pw := bar.ProxyWriter(io.Discard)
	_, err = io.Copy(pw, resp.Body)
	if err != nil {
		panic(err)
	}
}

The output is as follows:

0.00 b  10s

Notice that it continues to show 0.00b

Interestingly (and without totally understanding the code base), I looked at proxywriter.go in function newProxyWriter and noticed lines 62-64:

pw := proxyWriter{wc, b}
if _, ok := w.(io.ReaderFrom); ok {
    return proxyReaderFrom{pw}
}
return pw

If I remove that check so that the pw is returned, the bytes are displayed correctly.

For example:

19.00 b  10s

[vbauerster]

Hi! Thanks for example and report. I've refactored implementation in 9050bce which should fix the issue with ProxyWriter.

However in your example you still need to call following at the very end of main.

  bar.SetTotal(-1, true) // because you initialized bar with total <= 0
  p.Wait() // let bar gracefully render and shutdown itself (it's the reason why you got 19.00 b instead of 20.00 b)

If you pass real io.Writer like *os.File into ProxyWriter don't forget to defer pw.Close().

Will appreciate if you can confirm that recent commits have fixed this.

[AlexThurston]

Hey @vbauerster looks like things are working like a charm. Thanks for the very quick response time.