panic: "The Promise Sender was dropped" #25
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This was referenced Jan 19, 2024
emilk
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### What * Introduced in #4841 `poll-promise` has a gotcha: if you drop the `Sender` without sending a result,, the `Promise` will panic when polled. I opened an issue about this: EmbarkStudios/poll-promise#25 ### Checklist * [x] I have read and agree to [Contributor Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and the [Code of Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md) * [x] I've included a screenshot or gif (if applicable) * [x] I have tested the web demo (if applicable): * Using newly built examples: [app.rerun.io](https://app.rerun.io/pr/4872/index.html) * Using examples from latest `main` build: [app.rerun.io](https://app.rerun.io/pr/4872/index.html?manifest_url=https://app.rerun.io/version/main/examples_manifest.json) * Using full set of examples from `nightly` build: [app.rerun.io](https://app.rerun.io/pr/4872/index.html?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json) * [x] The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG - [PR Build Summary](https://build.rerun.io/pr/4872) - [Docs preview](https://rerun.io/preview/bdbdc1f71719e792869be347ebef16bcb318f2dd/docs) <!--DOCS-PREVIEW--> - [Examples preview](https://rerun.io/preview/bdbdc1f71719e792869be347ebef16bcb318f2dd/examples) <!--EXAMPLES-PREVIEW--> - [Recent benchmark results](https://build.rerun.io/graphs/crates.html) - [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)
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poll-promisepanics if the user drops theSenderbefore sending a value.This is quite a footgun.
A dropped sender is a bug (because we cannot deliver a value), but I'm not sure it deserves a crash.
We could change the interface of
Promiseto return a Result, with an error for "DroppedSender".We could also consider having the panic only in debug builds, and in release builds treat a dropped receiver the same as a receiver that hasn't sent anything yet, i.e. the promise will be stuck in "Pending" forever. Perhaps with a logged warning.
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