Implement TryFrom<std::process::Child> for tokio::process::Child
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Currently, you can turn a `std::process::Command` into a `tokio::process::Command`, however, if you have a `std::process::Child` there is no way to turn it into a `tokio::process::Child`. This provides a mechanism. ## Context The use case I'm after is this: I have a small crate for running commands in Rust. I was wondering what a `tokio` feature might look like when I hit a bit of a snag. I can't find a reliable way to convert a `std::process:Child` into something `await`-able. The primary interface is this trait https://docs.rs/fun_run/0.6.0/fun_run/trait.CommandWithName.html. It is implemented for `Command` and `&mut Command`. If I want to add a feature flagged `async fn spawn` for `tokio::process::Command`, then I also need a way to reproduce the same interface in my other already-existing implementations. My thought was that for the default implementation, I can produce a regular `std::process::Child` and then, if I can turn it into a `tokio::process::Child`. Then I can standardize on that interface.
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Darksonn
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ipetkov
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Jun 8, 2025
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| let spawned_child = imp::build_child(value)?; | ||
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| Ok(Child { | ||
| child: FusedChild::Child(ChildDropGuard { | ||
| inner: spawned_child.child, | ||
| kill_on_drop: false, | ||
| }), | ||
| stdin: spawned_child.stdin.map(|inner| ChildStdin { inner }), | ||
| stdout: spawned_child.stdout.map(|inner| ChildStdout { inner }), | ||
| stderr: spawned_child.stderr.map(|inner| ChildStderr { inner }), | ||
| }) |
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Rather than duplicate all this I'd prefer if we turned this into a call to Command::build_child so that these implementations never drift
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Whoops we can't call Command::build_child because it takes self, but effectively we should DRY these with a common helper
ipetkov
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Jun 8, 2025
| Ok(Child { | ||
| child: FusedChild::Child(ChildDropGuard { | ||
| inner: spawned_child.child, | ||
| kill_on_drop: false, |
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This might end up being a foot gun, there's no way to specify kill_on_drop: true. Maybe instead of using TryFrom we should add a conversion method? That way we can take an extra parameter (or more easily deprecate it in the future if necessary)
Darksonn
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Jun 9, 2025
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We don't add things to the changelog in PRs.
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Currently, you can turn a
std::process::Commandinto atokio::process::Command, however, if you have astd::process::Childthere is no way to turn it into atokio::process::Child. This provides a mechanism.Motivation
I have a small crate for running commands in Rust. I was wondering what a
tokiofeature might look like when I hit a bit of a snag. I can't find a reliable way to convert astd::process:Childinto somethingawait-able.The primary interface is this trait https://docs.rs/fun_run/0.6.0/fun_run/trait.CommandWithName.html. It is implemented for
Commandand&mut Command. If I want to add a feature flaggedasync fn spawnfortokio::process::Command, then I also need a way to reproduce the same interface in my other already-existing implementations. My thought was that for the default implementation, I can produce a regularstd::process::Childand then, if I can turn it into atokio::process::Child. Then I can standardize on that interface.Solution
Implementation: The code is taken nearly wholesale from
tokio::process::build_child(&self, child: StdChild). It's pretty much the exact thing that happens whentokio::process::Command::spawnis called, after the process is spawned.