bg: ensure init is complete before returning

[rusq]

I encountered an issue, where i started Auth immediately after calling Connect, and it seems that the Auth kicked in before the client.Run has finished initialisation.

The code that revealed the problem:

// for context
type Client {
	cl *telegram.Client
	auth auth.UserAuthenticator
	sendcodeOpts auth.SendCodeOptions
}

func (c *Client) Start(ctx context.Context) error {
// <...>

	stop, err := bg.Connect(c.cl)
	if err != nil {
		return err
	}

	// time.Sleep(500*time.Millisecond) // works around the issue

	flow := auth.NewFlow(c.auth, c.sendcodeOpts)
	if err := c.cl.Auth().IfNecessary(ctx, flow); err != nil {
		return err
	}
	log.Println("auth success")

}

To confirm this theory, I added a time.Sleep(500*time.Millisecond) after Connect, and before Auth (as shown on the commented line above)

Introducing the synchronisation in Connect fixes the described problem.

[rusq]

FIXED: If the Run errors out, the error is not returned until the wg.Wait() returns it, and wg.Wait is called only in Stop(), which is usually deferred. Consider the following example:

With (c *Client) defined as:

type Client struct {
  cl *telegram.Client
  auth         auth.UserAuthenticator
  sendcodeOpts auth.SendCodeOptions
}

// func (c *Client) Run() error {
stop, err := bg.Connect(c.cl)
if err != nil {
  return err
}
defer func() {
  if err := stop(); err!=nil {
    log.Print(err)
  }
}()
// even if Run fails with error, we will reach this point


flow := auth.NewFlow(c.auth, c.sendcodeOpts)

// *** the following will hang indefinitely ***
if err := c.cl.Auth().IfNecessary(ctx, flow); err != nil {
  return err
}

log.Debug("auth success")

return nil
}

[codecov]

Codecov Report

Merging #216 (cea888c) into master (9a5b21a) will increase coverage by 16.39%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #216       +/-   ##
===========================================
+ Coverage   55.47%   71.87%   +16.39%     
===========================================
  Files          48        9       -39     
  Lines        1871      256     -1615     
===========================================
- Hits         1038      184      -854     
+ Misses        752       51      -701     
+ Partials       81       21       -60     

Impacted Files	Coverage Δ
bg/connect.go
bbolt/auth.go
invoker/debug.go
auth/terminal/code.go
storage/find.go
auth/localization/catalog.go
pebble/peer_storage.go
middleware/floodwait/queue.go
invoker/update.go
storage/peer_as.go
... and 29 more

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