Allow empty DSN instead of returning an error

[chuyeow]

Based on

sentry-go/client.go

Line 130 in e3426d1

Logger.Println("Sentry client initialized with an empty DSN")

, it looks like the intent is to allow an empty DSN (e.g. when the SENTRY_DSN env var is not set).

The current behavior when the DSN is empty is to return an error from NewClient(). This PR allows the DSN to be empy.

[kamilogorek]

Thanks for filling a PR!

To make it fully functional, we need to also create NoopTransport which implements Transport interface and just logs information about the error being dropped. With the current code, transport will still be installed and it'll try to create Dsn which will fail -

sentry-go/transport.go

Lines 100 to 104 in e3426d1

	dsn, err := NewDsn(options.Dsn)
	if err != nil {
	Logger.Printf("%v\n", err)
	return
	}

We need to use NoopTransport as the default transport for empty Dsn scenario instead.

[chuyeow]

With the current code, transport will still be installed and it'll try to create Dsn which will fail

Whoops, I hadn't expected that. I'd assumed that because the global Hub has no Client bound (

sentry-go/hub.go

Line 24 in e3426d1

var currentHub = NewHub(nil, NewScope()) // nolint: gochecknoglobals

), it will "do the right thing" and do nothing. Can you confirm that my thinking is wrong? I just looked at

sentry-go/sentry.go

Lines 39 to 40 in e3426d1

	hub := CurrentHub()
	return hub.CaptureException(exception)

and

sentry-go/hub.go

Lines 172 to 174 in e3426d1

	client, scope := hub.Client(), hub.Scope()
	if client == nil || scope == nil {
	return nil

and it looks to me that since hub.Client() is nil, nothing is done.

[kamilogorek]

It binds a client during the first init call, and your change makes empty DSN not return an error, thus it will be bound correctly.

https://github.com/getsentry/sentry-go/blob/master/sentry.go#L12-L20

Current output when calling init will be:

[Sentry] 2019/07/09 15:20:01 Sentry client initialized with an empty DSN
[Sentry] 2019/07/09 15:20:01 [Sentry] DsnParseError: invalid scheme

We need to disable transport (or use noop) and log information about it.

[kamilogorek]

Closed in favor of #27
@chuyeow your commit is preserved :)

[chuyeow]

@kamilogorek woah thanks for doing that! I couldn’t find the time to work on this before, sorry for the late response.

[kamilogorek]

No worries! Thanks :)