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Fix 'panic: sync: negative WaitGroup counter' #1427

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Fix 'panic: sync: negative WaitGroup counter' #1427

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22 changes: 6 additions & 16 deletions allocate.go
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Expand Up @@ -211,9 +211,6 @@ func (a *ExecAllocator) Allocate(ctx context.Context, opts ...BrowserOption) (*B
case <-c.allocated: // for this browser's root context
}
a.wg.Add(1) // for the entire allocator
if a.combinedOutputWriter != nil {
a.wg.Add(1) // for the io.Copy in a separate goroutine
}
go func() {
// First wait for the process to be finished.
// TODO: do we care about this error in any scenario? if the
Expand All @@ -239,7 +236,7 @@ func (a *ExecAllocator) Allocate(ctx context.Context, opts ...BrowserOption) (*B
var wsURL string
wsURLChan := make(chan struct{}, 1)
go func() {
wsURL, err = readOutput(stdout, a.combinedOutputWriter, a.wg.Done)
wsURL, err = readOutput(stdout, a.combinedOutputWriter, &a.wg)
wsURLChan <- struct{}{}
}()
select {
Expand All @@ -248,11 +245,6 @@ func (a *ExecAllocator) Allocate(ctx context.Context, opts ...BrowserOption) (*B
err = errors.New("websocket url timeout reached")
}
if err != nil {
if a.combinedOutputWriter != nil {
// There's no io.Copy goroutine to call the done func.
// TODO: a cleaner way to deal with this edge case?
a.wg.Done()
}
return nil, err
}

Expand Down Expand Up @@ -282,11 +274,10 @@ func (a *ExecAllocator) Allocate(ctx context.Context, opts ...BrowserOption) (*B
// readOutput grabs the websocket address from chrome's output, returning as
// soon as it is found. All read output is forwarded to forward, if non-nil.
// done is used to signal that the asynchronous io.Copy is done, if any.
func readOutput(rc io.ReadCloser, forward io.Writer, done func()) (wsURL string, _ error) {
func readOutput(rc io.ReadCloser, forward io.Writer, wg *sync.WaitGroup) (wsURL string, _ error) {
prefix := []byte("DevTools listening on")
var accumulated bytes.Buffer
bufr := bufio.NewReader(rc)
readLoop:
for {
line, err := bufr.ReadBytes('\n')
if err != nil {
Expand All @@ -300,11 +291,9 @@ readLoop:
}

if bytes.HasPrefix(line, prefix) {
line = line[len(prefix):]
// use TrimSpace, to also remove \r on Windows
line = bytes.TrimSpace(line)
wsURL = string(line)
break readLoop
wsURL = string(bytes.TrimSpace(line[len(prefix):]))
break
}
accumulated.Write(line)
}
Expand All @@ -314,9 +303,10 @@ readLoop:
} else {
// Copy the rest of the output in a separate goroutine, as we
// need to return with the websocket URL.
wg.Add(1)
go func() {
io.Copy(forward, bufr)
done()
wg.Done()
}()
}
return wsURL, nil
Expand Down