async-compat-0.2.3/.cargo_vcs_info.json0000644000000001360000000000100134340ustar { "git": { "sha1": "d0f4e80b7abf50422ae1289a8bb9fb3c56641e4e" }, "path_in_vcs": "" }async-compat-0.2.3/.github/dependabot.yml000064400000000000000000000002331046102023000164120ustar 00000000000000version: 2 updates: - package-ecosystem: cargo directory: / schedule: interval: weekly commit-message: prefix: '' labels: [] async-compat-0.2.3/.github/workflows/ci.yml000064400000000000000000000032001046102023000167320ustar 00000000000000name: CI permissions: contents: read on: pull_request: push: branches: - master schedule: - cron: '0 2 * * 0' env: CARGO_INCREMENTAL: 0 CARGO_NET_GIT_FETCH_WITH_CLI: true CARGO_NET_RETRY: 10 CARGO_TERM_COLOR: always RUST_BACKTRACE: 1 RUSTFLAGS: -D warnings RUSTDOCFLAGS: -D warnings RUSTUP_MAX_RETRIES: 10 defaults: run: shell: bash jobs: test: runs-on: ${{ matrix.os }} strategy: fail-fast: false matrix: os: [ubuntu-latest] rust: [nightly, beta, stable] steps: - uses: actions/checkout@v4 - name: Install Rust run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }} - run: cargo build --all --all-features --all-targets - name: Run cargo check (without dev-dependencies to catch missing feature flags) if: startsWith(matrix.rust, 'nightly') run: cargo check -Z features=dev_dep - run: cargo test clippy: runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 - name: Install Rust run: rustup update stable - run: cargo clippy --all-features --all-targets fmt: runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 - name: Install Rust run: rustup update stable - run: cargo fmt --all --check security_audit: permissions: checks: write contents: read issues: write runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 # https://github.com/rustsec/audit-check/issues/2 - uses: rustsec/audit-check@master with: token: ${{ secrets.GITHUB_TOKEN }} async-compat-0.2.3/.github/workflows/release.yml000064400000000000000000000006411046102023000177650ustar 00000000000000name: Release permissions: contents: write on: push: tags: - v[0-9]+.* jobs: create-release: if: github.repository_owner == 'smol-rs' runs-on: ubuntu-latest steps: - uses: actions/checkout@v4 - uses: taiki-e/create-gh-release-action@v1 with: changelog: CHANGELOG.md branch: master env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} async-compat-0.2.3/.gitignore000064400000000000000000000000231046102023000142070ustar 00000000000000/target Cargo.lock async-compat-0.2.3/CHANGELOG.md000064400000000000000000000007671046102023000140470ustar 00000000000000# Version 0.2.3 - Enter the `tokio` context while dropping wrapped `tokio` types. (#22) # Version 0.2.2 - Add `smol-rs` logo to the docs. (#19) # Version 0.2.1 - Fix a bug in `AsyncSeek` implementation. # Version 0.2.0 - Update tokio to v1. # Version 0.1.5 - Add tokio v0.3 support. # Version 0.1.4 - Add `Compat::get_ref()`. - Add `Compat::get_mut()`. # Version 0.1.3 - More elaborate docs. # Version 0.1.2 - More docs. # Version 0.1.1 - More docs. # Version 0.1.0 - Initial version async-compat-0.2.3/Cargo.toml0000644000000030360000000000100114340ustar # THIS FILE IS AUTOMATICALLY GENERATED BY CARGO # # When uploading crates to the registry Cargo will automatically # "normalize" Cargo.toml files for maximal compatibility # with all versions of Cargo and also rewrite `path` dependencies # to registry (e.g., crates.io) dependencies. # # If you are reading this file be aware that the original Cargo.toml # will likely look very different (and much more reasonable). # See Cargo.toml.orig for the original contents. [package] edition = "2018" name = "async-compat" version = "0.2.3" authors = ["Stjepan Glavina "] description = "Compatibility adapter between tokio and futures" homepage = "https://github.com/smol-rs/async-compat" documentation = "https://docs.rs/async-compat" readme = "README.md" keywords = [ "tokio", "futures", "convert", "context", ] categories = ["asynchronous"] license = "Apache-2.0 OR MIT" repository = "https://github.com/smol-rs/async-compat" [dependencies.futures-core] version = "0.3.5" [dependencies.futures-io] version = "0.3.5" [dependencies.once_cell] version = "1.4.1" [dependencies.pin-project-lite] version = "0.2" [dependencies.tokio] version = "1" features = ["rt"] default-features = false [dev-dependencies.blocking] version = "1" [dev-dependencies.futures] version = "0.3.5" [dev-dependencies.reqwest] version = "0.11" [dev-dependencies.tokio] version = "1" features = [ "rt-multi-thread", "io-std", "io-util", "macros", "net", "time", ] default-features = false [dev-dependencies.warp] version = "0.3" async-compat-0.2.3/Cargo.toml.orig000064400000000000000000000016351046102023000151200ustar 00000000000000[package] name = "async-compat" # When publishing a new version: # - Update CHANGELOG.md # - Create "v0.x.y" git tag version = "0.2.3" authors = ["Stjepan Glavina "] edition = "2018" description = "Compatibility adapter between tokio and futures" license = "Apache-2.0 OR MIT" repository = "https://github.com/smol-rs/async-compat" homepage = "https://github.com/smol-rs/async-compat" documentation = "https://docs.rs/async-compat" keywords = ["tokio", "futures", "convert", "context"] categories = ["asynchronous"] [dependencies] futures-core = "0.3.5" futures-io = "0.3.5" once_cell = "1.4.1" pin-project-lite = "0.2" tokio = { version = "1", default-features = false, features = ["rt"] } [dev-dependencies] blocking = "1" futures = "0.3.5" reqwest = "0.11" tokio = { version = "1", default-features = false, features = ["rt-multi-thread", "io-std", "io-util", "macros", "net", "time"] } warp = "0.3" async-compat-0.2.3/LICENSE-APACHE000064400000000000000000000251371046102023000141600ustar 00000000000000 Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. 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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. async-compat-0.2.3/README.md000064400000000000000000000116251046102023000135100ustar 00000000000000# async-compat [![Build](https://github.com/smol-rs/async-compat/workflows/Build%20and%20test/badge.svg)]( https://github.com/smol-rs/async-compat/actions) [![License](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)]( https://github.com/smol-rs/async-compat) [![Cargo](https://img.shields.io/crates/v/async-compat.svg)]( https://crates.io/crates/async-compat) [![Documentation](https://docs.rs/async-compat/badge.svg)]( https://docs.rs/async-compat) Compatibility adapter between tokio and futures. There are two kinds of compatibility issues between [tokio] and [futures]: 2. Tokio's types cannot be used outside tokio context, so any attempt to use them will panic. - Solution: If you apply the `Compat` adapter to a future, the future will enter the context of a global single-threaded tokio runtime started by this crate. That does *not* mean the future runs on the tokio runtime - it only means the future sets a thread-local variable pointing to the global tokio runtime so that tokio's types can be used inside it. 2. Tokio and futures have similar but different I/O traits `AsyncRead`, `AsyncWrite`, `AsyncBufRead`, and `AsyncSeek`. - Solution: When the `Compat` adapter is applied to an I/O type, it will implement traits of the opposite kind. That's how you can use tokio-based types wherever futures-based types are expected, and the other way around. ## Examples This program reads lines from stdin and echoes them into stdout, except it's not going to work: ```rust fn main() -> std::io::Result<()> { futures::executor::block_on(async { let stdin = tokio::io::stdin(); let mut stdout = tokio::io::stdout(); // The following line will not work for two reasons: // 1. Runtime error because stdin and stdout are used outside tokio context. // 2. Compilation error due to mismatched `AsyncRead` and `AsyncWrite` traits. futures::io::copy(stdin, &mut stdout).await?; Ok(()) }) } ``` To get around the compatibility issues, apply the `Compat` adapter to `stdin`, `stdout`, and [`futures::io::copy()`]: ```rust use async_compat::CompatExt; fn main() -> std::io::Result<()> { futures::executor::block_on(async { let stdin = tokio::io::stdin(); let mut stdout = tokio::io::stdout(); futures::io::copy(stdin.compat(), &mut stdout.compat_mut()).compat().await?; Ok(()) }) } ``` It is also possible to apply `Compat` to the outer future passed to [`futures::executor::block_on()`] rather than [`futures::io::copy()`] itself. When applied to the outer future, individual inner futures don't need the adapter because they're all now inside tokio context: ```rust use async_compat::{Compat, CompatExt}; fn main() -> std::io::Result<()> { futures::executor::block_on(Compat::new(async { let stdin = tokio::io::stdin(); let mut stdout = tokio::io::stdout(); futures::io::copy(stdin.compat(), &mut stdout.compat_mut()).await?; Ok(()) })) } ``` The compatibility adapter converts between tokio-based and futures-based I/O types in any direction. Here's how we can write the same program by using futures-based I/O types inside tokio: ```rust use async_compat::CompatExt; use blocking::Unblock; #[tokio::main] async fn main() -> std::io::Result<()> { let mut stdin = Unblock::new(std::io::stdin()); let mut stdout = Unblock::new(std::io::stdout()); tokio::io::copy(&mut stdin.compat_mut(), &mut stdout.compat_mut()).await?; Ok(()) } ``` Finally, we can use any tokio-based crate from any other async runtime. Here are [reqwest] and [warp] as an example: ```rust use async_compat::{Compat, CompatExt}; use warp::Filter; fn main() { futures::executor::block_on(Compat::new(async { // Make an HTTP GET request. let response = reqwest::get("https://www.rust-lang.org").await.unwrap(); println!("{}", response.text().await.unwrap()); // Start an HTTP server. let routes = warp::any().map(|| "Hello from warp!"); warp::serve(routes).run(([127, 0, 0, 1], 8080)).await; })) } ``` [blocking]: https://docs.rs/blocking [futures]: https://docs.rs/futures [reqwest]: https://docs.rs/reqwest [tokio]: https://docs.rs/tokio [warp]: https://docs.rs/warp [`futures::io::copy()`]: https://docs.rs/futures/0.3/futures/io/fn.copy.html [`futures::executor::block_on()`]: https://docs.rs/futures/0.3/futures/executor/fn.block_on.html ## License Licensed under either of * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0) * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT) at your option. #### Contribution Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions. async-compat-0.2.3/src/lib.rs000064400000000000000000000345601046102023000141370ustar 00000000000000//! Compatibility adapter between tokio and futures. //! //! There are two kinds of compatibility issues between [tokio] and [futures]: //! //! 1. Tokio's types cannot be used outside tokio context, so any attempt to use //! them will panic. //! - Solution: If you apply the [`Compat`] adapter to a future, the future will enter the //! context of a global single-threaded tokio runtime started by this crate. That does //! *not* mean the future runs on the tokio runtime - it only means the future sets a //! thread-local variable pointing to the global tokio runtime so that tokio's types can be //! used inside it. //! 2. Tokio and futures have similar but different I/O traits `AsyncRead`, `AsyncWrite`, //! `AsyncBufRead`, and `AsyncSeek`. //! - Solution: When the [`Compat`] adapter is applied to an I/O type, it will implement traits //! of the opposite kind. That's how you can use tokio-based types wherever futures-based //! types are expected, and the other way around. //! //! You can apply the [`Compat`] adapter using the [`Compat::new()`] constructor or using any //! method from the [`CompatExt`] trait. //! //! # Examples //! //! This program reads lines from stdin and echoes them into stdout, except it's not going to work: //! //! ```compile_fail //! fn main() -> std::io::Result<()> { //! futures::executor::block_on(async { //! let stdin = tokio::io::stdin(); //! let mut stdout = tokio::io::stdout(); //! //! // The following line will not work for two reasons: //! // 1. Runtime error because stdin and stdout are used outside tokio context. //! // 2. Compilation error due to mismatched `AsyncRead` and `AsyncWrite` traits. //! futures::io::copy(stdin, &mut stdout).await?; //! Ok(()) //! }) //! } //! ``` //! //! To get around the compatibility issues, apply the [`Compat`] adapter to `stdin`, `stdout`, and //! [`futures::io::copy()`]: //! //! ``` //! use async_compat::CompatExt; //! //! fn main() -> std::io::Result<()> { //! futures::executor::block_on(async { //! let stdin = tokio::io::stdin(); //! let mut stdout = tokio::io::stdout(); //! //! futures::io::copy(stdin.compat(), &mut stdout.compat_mut()).compat().await?; //! Ok(()) //! }) //! } //! ``` //! //! It is also possible to apply [`Compat`] to the outer future passed to //! [`futures::executor::block_on()`] rather than [`futures::io::copy()`] itself. //! When applied to the outer future, individual inner futures don't need the adapter because //! they're all now inside tokio context: //! //! ```no_run //! use async_compat::{Compat, CompatExt}; //! //! fn main() -> std::io::Result<()> { //! futures::executor::block_on(Compat::new(async { //! let stdin = tokio::io::stdin(); //! let mut stdout = tokio::io::stdout(); //! //! futures::io::copy(stdin.compat(), &mut stdout.compat_mut()).await?; //! Ok(()) //! })) //! } //! ``` //! //! The compatibility adapter converts between tokio-based and futures-based I/O types in any //! direction. Here's how we can write the same program by using futures-based I/O types inside //! tokio: //! //! ```no_run //! use async_compat::CompatExt; //! use blocking::Unblock; //! //! #[tokio::main] //! async fn main() -> std::io::Result<()> { //! let mut stdin = Unblock::new(std::io::stdin()); //! let mut stdout = Unblock::new(std::io::stdout()); //! //! tokio::io::copy(&mut stdin.compat_mut(), &mut stdout.compat_mut()).await?; //! Ok(()) //! } //! ``` //! //! Finally, we can use any tokio-based crate from any other async runtime. //! Here are [reqwest] and [warp] as an example: //! //! ```no_run //! use async_compat::{Compat, CompatExt}; //! use warp::Filter; //! //! fn main() { //! futures::executor::block_on(Compat::new(async { //! // Make an HTTP GET request. //! let response = reqwest::get("https://www.rust-lang.org").await.unwrap(); //! println!("{}", response.text().await.unwrap()); //! //! // Start an HTTP server. //! let routes = warp::any().map(|| "Hello from warp!"); //! warp::serve(routes).run(([127, 0, 0, 1], 8080)).await; //! })) //! } //! ``` //! //! [blocking]: https://docs.rs/blocking //! [futures]: https://docs.rs/futures //! [reqwest]: https://docs.rs/reqwest //! [tokio]: https://docs.rs/tokio //! [warp]: https://docs.rs/warp //! [`futures::io::copy()`]: https://docs.rs/futures/0.3/futures/io/fn.copy.html //! [`futures::executor::block_on()`]: https://docs.rs/futures/0.3/futures/executor/fn.block_on.html #![allow(clippy::needless_doctest_main)] #![doc( html_favicon_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png" )] #![doc( html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png" )] use std::future::Future; use std::io; use std::pin::Pin; use std::task::{Context, Poll}; use std::thread; use futures_core::ready; use once_cell::sync::Lazy; use pin_project_lite::pin_project; /// Applies the [`Compat`] adapter to futures and I/O types. pub trait CompatExt { /// Applies the [`Compat`] adapter by value. /// /// # Examples /// /// ``` /// use async_compat::CompatExt; /// /// let stdout = tokio::io::stdout().compat(); /// ``` fn compat(self) -> Compat where Self: Sized; /// Applies the [`Compat`] adapter by shared reference. /// /// # Examples /// /// ``` /// use async_compat::CompatExt; /// /// let original = tokio::io::stdout(); /// let stdout = original.compat_ref(); /// ``` fn compat_ref(&self) -> Compat<&Self>; /// Applies the [`Compat`] adapter by mutable reference. /// /// # Examples /// /// ``` /// use async_compat::CompatExt; /// /// let mut original = tokio::io::stdout(); /// let stdout = original.compat_mut(); /// ``` fn compat_mut(&mut self) -> Compat<&mut Self>; } impl CompatExt for T { fn compat(self) -> Compat where Self: Sized, { Compat::new(self) } fn compat_ref(&self) -> Compat<&Self> { Compat::new(self) } fn compat_mut(&mut self) -> Compat<&mut Self> { Compat::new(self) } } pin_project! { /// Compatibility adapter for futures and I/O types. pub struct Compat { #[pin] inner: Option, seek_pos: Option, } impl PinnedDrop for Compat { fn drop(this: Pin<&mut Self>) { if this.inner.is_some() { // If the inner future wasn't moved out using into_inner, // enter the tokio context while the inner value is dropped. let _guard = TOKIO1.enter(); this.project().inner.set(None); } } } } impl Compat { /// Applies the compatibility adapter to a future or an I/O type. /// /// # Examples /// /// Apply it to a future: /// /// ``` /// use async_compat::Compat; /// use std::time::Duration; /// /// futures::executor::block_on(Compat::new(async { /// // We can use tokio's timers because we're inside tokio context. /// tokio::time::sleep(Duration::from_secs(1)).await; /// })); /// ``` /// /// Apply it to an I/O type: /// /// ``` /// use async_compat::{Compat, CompatExt}; /// use futures::prelude::*; /// /// # fn main() -> std::io::Result<()> { /// futures::executor::block_on(Compat::new(async { /// // The `write_all` method comes from `futures::io::AsyncWriteExt`. /// Compat::new(tokio::io::stdout()).write_all(b"hello\n").await?; /// Ok(()) /// })) /// # } /// ``` pub fn new(t: T) -> Compat { Compat { inner: Some(t), seek_pos: None, } } /// Gets a shared reference to the inner value. /// /// # Examples /// /// ``` /// use async_compat::Compat; /// use tokio::net::UdpSocket; /// /// # fn main() -> std::io::Result<()> { /// futures::executor::block_on(Compat::new(async { /// let socket = Compat::new(UdpSocket::bind("127.0.0.1:0").await?); /// let addr = socket.get_ref().local_addr()?; /// Ok(()) /// })) /// # } /// ``` pub fn get_ref(&self) -> &T { self.inner .as_ref() .expect("inner is only None when Compat is about to drop") } /// Gets a mutable reference to the inner value. /// /// # Examples /// /// ```no_run /// use async_compat::Compat; /// use tokio::net::TcpListener; /// /// # fn main() -> std::io::Result<()> { /// futures::executor::block_on(Compat::new(async { /// let mut listener = Compat::new(TcpListener::bind("127.0.0.1:0").await?); /// let (stream, addr) = listener.get_mut().accept().await?; /// let stream = Compat::new(stream); /// Ok(()) /// })) /// # } /// ``` pub fn get_mut(&mut self) -> &mut T { self.inner .as_mut() .expect("inner is only None when Compat is about to drop") } fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut T> { self.project() .inner .as_pin_mut() .expect("inner is only None when Compat is about to drop") } /// Unwraps the compatibility adapter. /// /// # Examples /// /// ``` /// use async_compat::Compat; /// /// let stdout = Compat::new(tokio::io::stdout()); /// let original = stdout.into_inner(); /// ``` pub fn into_inner(mut self) -> T { self.inner .take() .expect("inner is only None when Compat is about to drop") } } impl Future for Compat { type Output = T::Output; fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll { let _guard = TOKIO1.enter(); self.get_pin_mut().poll(cx) } } impl futures_io::AsyncRead for Compat { fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8], ) -> Poll> { let mut buf = tokio::io::ReadBuf::new(buf); ready!(self.get_pin_mut().poll_read(cx, &mut buf))?; Poll::Ready(Ok(buf.filled().len())) } } impl tokio::io::AsyncRead for Compat { fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut tokio::io::ReadBuf<'_>, ) -> Poll> { let unfilled = buf.initialize_unfilled(); let poll = self.get_pin_mut().poll_read(cx, unfilled); if let Poll::Ready(Ok(num)) = &poll { buf.advance(*num); } poll.map_ok(|_| ()) } } impl futures_io::AsyncBufRead for Compat { fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { self.get_pin_mut().poll_fill_buf(cx) } fn consume(self: Pin<&mut Self>, amt: usize) { self.get_pin_mut().consume(amt) } } impl tokio::io::AsyncBufRead for Compat { fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { self.get_pin_mut().poll_fill_buf(cx) } fn consume(self: Pin<&mut Self>, amt: usize) { self.get_pin_mut().consume(amt) } } impl futures_io::AsyncWrite for Compat { fn poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll> { self.get_pin_mut().poll_write(cx, buf) } fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { self.get_pin_mut().poll_flush(cx) } fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { self.get_pin_mut().poll_shutdown(cx) } } impl tokio::io::AsyncWrite for Compat { fn poll_write( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll> { self.get_pin_mut().poll_write(cx, buf) } fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { self.get_pin_mut().poll_flush(cx) } fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { self.get_pin_mut().poll_close(cx) } } impl futures_io::AsyncSeek for Compat { fn poll_seek( mut self: Pin<&mut Self>, cx: &mut Context, pos: io::SeekFrom, ) -> Poll> { if self.seek_pos != Some(pos) { self.as_mut().get_pin_mut().start_seek(pos)?; *self.as_mut().project().seek_pos = Some(pos); } let res = ready!(self.as_mut().get_pin_mut().poll_complete(cx)); *self.as_mut().project().seek_pos = None; Poll::Ready(res) } } impl tokio::io::AsyncSeek for Compat { fn start_seek(mut self: Pin<&mut Self>, pos: io::SeekFrom) -> io::Result<()> { *self.as_mut().project().seek_pos = Some(pos); Ok(()) } fn poll_complete(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll> { let pos = match self.seek_pos { None => { // tokio 1.x AsyncSeek recommends calling poll_complete before start_seek. // We don't have to guarantee that the value returned by // poll_complete called without start_seek is correct, // so we'll return 0. return Poll::Ready(Ok(0)); } Some(pos) => pos, }; let res = ready!(self.as_mut().get_pin_mut().poll_seek(cx, pos)); *self.as_mut().project().seek_pos = None; Poll::Ready(res) } } static TOKIO1: Lazy = Lazy::new(|| { thread::Builder::new() .name("async-compat/tokio-1".to_string()) .spawn(move || TOKIO1.block_on(Pending)) .unwrap(); tokio::runtime::Builder::new_current_thread() .enable_all() .build() .expect("cannot start tokio-1 runtime") }); struct Pending; impl Future for Pending { type Output = (); fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll { Poll::Pending } }