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docs: provide an example to explain the cloning inner services #762

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docs: provide an example to explain the cloning inner services #762

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5 changes: 4 additions & 1 deletion tower-service/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -236,7 +236,10 @@ use std::task::{Context, Poll};
///
/// Services are permitted to panic if `call` is invoked without obtaining `Poll::Ready(Ok(()))`
/// from `poll_ready`. You should therefore be careful when cloning services for example to move
/// them into boxed futures. Even though the original service is ready, the clone might not be.
/// them into boxed futures. Even though the original service is ready, the clone might not be,
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I don't understand how ConcurrencyLimit exemplifies what this docs section is trying to convey. If you're referring to the fact that cloning an inner ConcurrencyLimit service resets the permit to unacquired and that poll_ready acquires it, that will only be understood by readers who have read ConcurrencyLimit's source code.

/// as in the case of the [`ConcurrencyLimit`] middleware.
///
/// [`ConcurrencyLimit`]: crate::limit::ConcurrencyLimit#impl-Clone
///
/// Therefore this kind of code is wrong and might panic:
///
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