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Blanket-implement tracing::instrument::WithSubscriber #1424

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hawkw merged 1 commit into from
Jun 7, 2021
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Blanket-implement tracing::instrument::WithSubscriber #1424

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2 changes: 2 additions & 0 deletions tracing/src/instrument.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -120,6 +120,8 @@ pub trait WithSubscriber: Sized {
}
}

impl<T: Sized> WithSubscriber for T {}
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@nightkr nightkr Jun 7, 2021

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The bound here is copied from tracing-futures. It might be worth adding a Future bound to avoid polluting autocompletes too much though?

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@hawkw hawkw Jun 7, 2021 •
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The tracing-futures version does not have a Future bound because it also allows wrapping types implementing other traits, such as Stream, with a subscriber. However, tracing's version only provides implementations for Future, because tracing depends only on the standard library, not the futures crate. So, it should be fine to restrict the blanket impl to T: Future, here.

However, when the Stream trait eventually does make it into std, we'll probably want to add a Stream impl for WithSubscriber<T: Stream>, as well. Then, we'll have to make the blanket impl more general. Technically, I think this is a breaking change, as it could break user WithSubscriber impls for types that don't implement Future. To protect against that, I think we would need to seal the trait so that downstream code can't add WithSubscriber impls. Then, it would be fine to add a Future bound on the blanket impl, for now.


pin_project! {
/// A future that has been instrumented with a `tracing` subscriber.
#[derive(Clone, Debug)]
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