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sync: doc of watch::Sender::send improved #4959
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Current documentation of `sync::watch::Sender::send` may be intepreted as the method failing if at some point in past the channel has been closed because every receiver has been dropped. This isn't true, however, as the channel could have been reopened by using `sync::watch::Sender::subscribe`. This fix clarifies the behavior. Moreover, it is noted that on failure, the value isn't made available to future subscribers (but returned as part of the `SendError`). Fixes tokio-rs#4957.
@@ -604,8 +604,14 @@ impl<T> Drop for Receiver<T> { | |||
impl<T> Sender<T> { | |||
/// Sends a new value via the channel, notifying all receivers. | |||
/// | |||
/// This method fails if the channel has been closed, which happens when | |||
/// every receiver has been dropped. | |||
/// This method fails if the channel is closed, which is the case when |
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Maybe it would be worth adding something like "unlike the other methods for sending" to emphasize that only this method fails in this way.
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Thank you for pointing that out; I added another note, mentioning that the other send methods can be used to send a value even if there isn't any receiver.
sync: doc of watch::Sender::send improved Current documentation of `sync::watch::Sender::send` may be intepreted as the method failing if at some point in past the channel has been closed because every receiver has been dropped. This isn't true, however, as the channel could have been reopened by using `sync::watch::Sender::subscribe`. This fix clarifies the behavior. Moreover, it is noted that on failure, the value isn't made available to future subscribers (but returned as part of the `SendError`), and that the other send methods (`send_if_modified`, `send_modify`, or `send_replace`) can be used to always make a new value available for future receivers, even if no receiver currently exists. Fixes tokio-rs#4957.
Thanks! |
You'll need to merge master to pass CI. |
Should I create a merge commit or rebase? |
Once a PR is open, it is preferable to create a merge commit, the changes will be squashed when they're merged. |
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Thanks.
This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dependencies | minor | `1.20.1` -> `1.21.0` | | [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dev-dependencies | minor | `1.20.1` -> `1.21.0` | --- ### Release Notes <details> <summary>tokio-rs/tokio</summary> ### [`v1.21.0`](https://github.com/tokio-rs/tokio/releases/tag/tokio-1.21.0) [Compare Source](tokio-rs/tokio@tokio-1.20.1...tokio-1.21.0) ##### 1.21.0 (September 2, 2022) This release is the first release of Tokio to intentionally support WASM. The `sync,macros,io-util,rt,time` features are stabilized on WASM. Additionally the wasm32-wasi target is given unstable support for the `net` feature. ##### Added - net: add `device` and `bind_device` methods to TCP/UDP sockets ([#​4882]) - net: add `tos` and `set_tos` methods to TCP and UDP sockets ([#​4877]) - net: add security flags to named pipe `ServerOptions` ([#​4845]) - signal: add more windows signal handlers ([#​4924]) - sync: add `mpsc::Sender::max_capacity` method ([#​4904]) - sync: implement Weak version of `mpsc::Sender` ([#​4595]) - task: add `LocalSet::enter` ([#​4765]) - task: stabilize `JoinSet` and `AbortHandle` ([#​4920]) - tokio: add `track_caller` to public APIs ([#​4805], [#​4848], [#​4852]) - wasm: initial support for `wasm32-wasi` target ([#​4716]) ##### Fixed - miri: improve miri compatibility by avoiding temporary references in `linked_list::Link` impls ([#​4841]) - signal: don't register write interest on signal pipe ([#​4898]) - sync: add `#[must_use]` to lock guards ([#​4886]) - sync: fix hang when calling `recv` on closed and reopened broadcast channel ([#​4867]) - task: propagate attributes on task-locals ([#​4837]) ##### Changed - fs: change panic to error in `File::start_seek` ([#​4897]) - io: reduce syscalls in `poll_read` ([#​4840]) - process: use blocking threadpool for child stdio I/O ([#​4824]) - signal: make `SignalKind` methods const ([#​4956]) ##### Internal changes - rt: extract `basic_scheduler::Config` ([#​4935]) - rt: move I/O driver into `runtime` module ([#​4942]) - rt: rename internal scheduler types ([#​4945]) ##### Documented - chore: fix typos and grammar ([#​4858], [#​4894], [#​4928]) - io: fix typo in `AsyncSeekExt::rewind` docs ([#​4893]) - net: add documentation to `try_read()` for zero-length buffers ([#​4937]) - runtime: remove incorrect panic section for `Builder::worker_threads` ([#​4849]) - sync: doc of `watch::Sender::send` improved ([#​4959]) - task: add cancel safety docs to `JoinHandle` ([#​4901]) - task: expand on cancellation of `spawn_blocking` ([#​4811]) - time: clarify that the first tick of `Interval::tick` happens immediately ([#​4951]) ##### Unstable - rt: add unstable option to disable the LIFO slot ([#​4936]) - task: fix incorrect signature in `Builder::spawn_on` ([#​4953]) - task: make `task::Builder::spawn*` methods fallible ([#​4823]) [#​4595]: tokio-rs/tokio#4595 [#​4716]: tokio-rs/tokio#4716 [#​4765]: tokio-rs/tokio#4765 [#​4805]: tokio-rs/tokio#4805 [#​4811]: tokio-rs/tokio#4811 [#​4823]: tokio-rs/tokio#4823 [#​4824]: tokio-rs/tokio#4824 [#​4837]: tokio-rs/tokio#4837 [#​4840]: tokio-rs/tokio#4840 [#​4841]: tokio-rs/tokio#4841 [#​4845]: tokio-rs/tokio#4845 [#​4848]: tokio-rs/tokio#4848 [#​4849]: tokio-rs/tokio#4849 [#​4852]: tokio-rs/tokio#4852 [#​4858]: tokio-rs/tokio#4858 [#​4867]: tokio-rs/tokio#4867 [#​4877]: tokio-rs/tokio#4877 [#​4882]: tokio-rs/tokio#4882 [#​4886]: tokio-rs/tokio#4886 [#​4893]: tokio-rs/tokio#4893 [#​4894]: tokio-rs/tokio#4894 [#​4897]: tokio-rs/tokio#4897 [#​4898]: tokio-rs/tokio#4898 [#​4901]: tokio-rs/tokio#4901 [#​4904]: tokio-rs/tokio#4904 [#​4920]: tokio-rs/tokio#4920 [#​4924]: tokio-rs/tokio#4924 [#​4928]: tokio-rs/tokio#4928 [#​4935]: tokio-rs/tokio#4935 [#​4936]: tokio-rs/tokio#4936 [#​4937]: tokio-rs/tokio#4937 [#​4942]: tokio-rs/tokio#4942 [#​4945]: tokio-rs/tokio#4945 [#​4951]: tokio-rs/tokio#4951 [#​4953]: tokio-rs/tokio#4953 [#​4956]: tokio-rs/tokio#4956 [#​4959]: tokio-rs/tokio#4959 </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about these updates again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click this checkbox. --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzMi4xODcuMCIsInVwZGF0ZWRJblZlciI6IjMyLjE4Ny4wIn0=--> Co-authored-by: cabr2-bot <cabr2.help@gmail.com> Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1532 Reviewed-by: crapStone <crapstone@noreply.codeberg.org> Co-authored-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org> Co-committed-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
Current documentation of
sync::watch::Sender::send
may be intepreted as the method failing if at some point in past the channel has been closed because every receiver has been dropped. This isn't true, however, as the channel could have been reopened by usingsync::watch::Sender::subscribe
.This fix clarifies the behavior. Moreover, it is noted that on failure, the value isn't made available to future subscribers (but returned as part of the
SendError
).Fixes #4957.