Why Span has an enter() method?

[psandana]

Why does this enter() method exists?
https://github.com/tokio-rs/tracing/blob/master/tracing/src/span.rs#L783

Can it be the Span object itself can hold the lifetime of the span?

[mladedav]

Because sometimes you want to enter it sometime later after its creation and sometimes you want to enter and exit it multiple times (for example instrumented futures do this).

[psandana]

Interesting point the latest. For the first I would expect a scope would be enough.

Thanks, I will explore more about that pattern.

[mladedav]

The problem with scopes is you need to have all fields available where you want to create the span.

For example

let span = info_span!("name", ?local_variable);
do_stuff.instrument(span).await;

becomes impossible and if you want to have the local variable in your span, you would have to pass it along.