tokio_macros/

lib.rs

#![allow(clippy::needless_doctest_main)]
#![warn(
    missing_debug_implementations,
    missing_docs,
    rust_2018_idioms,
    unreachable_pub
)]
#![doc(test(
    no_crate_inject,
    attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
))]

//! Macros for use with Tokio

mod entry;
mod select;

use proc_macro::TokenStream;

/// Marks async function to be executed by the selected runtime. This macro
/// helps set up a `Runtime` without requiring the user to use
/// [Runtime](../tokio/runtime/struct.Runtime.html) or
/// [Builder](../tokio/runtime/struct.Builder.html) directly.
///
/// Note: This macro is designed to be simplistic and targets applications that
/// do not require a complex setup. If the provided functionality is not
/// sufficient, you may be interested in using
/// [Builder](../tokio/runtime/struct.Builder.html), which provides a more
/// powerful interface.
///
/// Note: This macro can be used on any function and not just the `main`
/// function. Although the function is written with `async fn`, this macro
/// expands it to a synchronous function that starts a runtime each time it is
/// called. If the function is called often, it is preferable to create the
/// runtime using the runtime builder so the runtime can be reused across calls.
/// For details on the expansion, see [Bridging with sync code][bridging].
///
/// # Non-worker async function
///
/// Note that the async function marked with this macro does not run as a
/// worker. The expectation is that other tasks are spawned by the function here.
/// Awaiting on other futures from the function provided here will not
/// perform as fast as those spawned as workers.
///
/// # Runtime flavors
///
/// The macro can be configured with a `flavor` parameter to select
/// different runtime configurations.
///
/// ## Multi-threaded
///
/// To use the multi-threaded runtime, the macro can be configured using
///
/// ```
/// #[tokio::main(flavor = "multi_thread", worker_threads = 10)]
/// # async fn main() {}
/// ```
///
/// The `worker_threads` option configures the number of worker threads, and
/// defaults to the number of cpus on the system. This is the default flavor.
///
/// Note: The multi-threaded runtime requires the `rt-multi-thread` feature
/// flag.
///
/// ## Current-thread
///
/// To use the single-threaded runtime known as the `current_thread` runtime,
/// the macro can be configured using
///
/// ```rust
/// #[tokio::main(flavor = "current_thread")]
/// # async fn main() {}
/// ```
///
/// ## Local
///
/// To use the [local runtime], the macro can be configured using
///
/// ```rust
/// #[tokio::main(flavor = "local")]
/// # async fn main() {}
/// ```
///
/// # Function arguments
///
/// Arguments are allowed for any functions, aside from `main` which is special.
///
/// # Usage
///
/// ## Set the name of the runtime
///
/// ```rust
/// #[tokio::main(name = "my-runtime")]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_multi_thread()
///         .enable_all()
///         .name("my-runtime")
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// ## Using the multi-threaded runtime
///
/// ```rust
/// #[tokio::main]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_multi_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// ## Using the current-thread runtime
///
/// The basic scheduler is single-threaded.
///
/// ```rust
/// #[tokio::main(flavor = "current_thread")]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// ## Using the local runtime
///
/// The [local runtime] is similar to the current-thread runtime but
/// supports [`task::spawn_local`](../tokio/task/fn.spawn_local.html).
///
/// ```rust
/// #[tokio::main(flavor = "local")]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .build_local(tokio::runtime::LocalOptions::default())
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
///
/// ## Set number of worker threads
///
/// ```rust
/// #[tokio::main(worker_threads = 2)]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_multi_thread()
///         .worker_threads(2)
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// ## Configure the runtime to start with time paused
///
/// ```rust
/// #[tokio::main(flavor = "current_thread", start_paused = true)]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .start_paused(true)
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// Note that `start_paused` requires the `test-util` feature to be enabled.
///
/// ## Rename package
///
/// ```rust
/// use tokio as tokio1;
///
/// #[tokio1::main(crate = "tokio1")]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// use tokio as tokio1;
///
/// fn main() {
///     tokio1::runtime::Builder::new_multi_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// ## Configure unhandled panic behavior
///
/// Available options are `shutdown_runtime` and `ignore`. For more details, see
/// [`Builder::unhandled_panic`].
///
/// This option is only compatible with the `current_thread` runtime.
///
/// ```no_run
/// #[cfg(tokio_unstable)]
/// #[tokio::main(flavor = "current_thread", unhandled_panic = "shutdown_runtime")]
/// async fn main() {
///     let _ = tokio::spawn(async {
///         panic!("This panic will shutdown the runtime.");
///     }).await;
/// }
/// # #[cfg(not(tokio_unstable))]
/// # fn main() { }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```no_run
/// #[cfg(tokio_unstable)]
/// fn main() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .unhandled_panic(tokio::runtime::UnhandledPanic::ShutdownRuntime)
///         .build()
///         .unwrap()
///         .block_on(async {
///             let _ = tokio::spawn(async {
///                 panic!("This panic will shutdown the runtime.");
///             }).await;
///         })
/// }
/// # #[cfg(not(tokio_unstable))]
/// # fn main() { }
/// ```
///
/// **Note**: This option depends on Tokio's [unstable API][unstable]. See [the
/// documentation on unstable features][unstable] for details on how to enable
/// Tokio's unstable features.
///
/// [`Builder::unhandled_panic`]: ../tokio/runtime/struct.Builder.html#method.unhandled_panic
/// [unstable]: ../tokio/index.html#unstable-features
/// [local runtime]: ../tokio/runtime/struct.LocalRuntime.html
/// [bridging]: https://tokio.rs/tokio/topics/bridging#what-tokiomain-expands-to
#[proc_macro_attribute]
pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
    entry::main(args.into(), item.into(), true).into()
}

/// Marks async function to be executed by selected runtime. This macro helps set up a `Runtime`
/// without requiring the user to use [Runtime](../tokio/runtime/struct.Runtime.html) or
/// [Builder](../tokio/runtime/struct.Builder.html) directly.
///
/// ## Function arguments:
///
/// Arguments are allowed for any functions aside from `main` which is special
///
/// ## Usage
///
/// ### Using default
///
/// ```rust
/// #[tokio::main(flavor = "current_thread")]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// fn main() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
///
/// ### Rename package
///
/// ```rust
/// use tokio as tokio1;
///
/// #[tokio1::main(crate = "tokio1")]
/// async fn main() {
///     println!("Hello world");
/// }
/// ```
///
/// Equivalent code not using `#[tokio::main]`
///
/// ```rust
/// use tokio as tokio1;
///
/// fn main() {
///     tokio1::runtime::Builder::new_multi_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             println!("Hello world");
///         })
/// }
/// ```
#[proc_macro_attribute]
pub fn main_rt(args: TokenStream, item: TokenStream) -> TokenStream {
    entry::main(args.into(), item.into(), false).into()
}

/// Marks async function to be executed by runtime, suitable to test environment.
/// This macro helps set up a `Runtime` without requiring the user to use
/// [Runtime](../tokio/runtime/struct.Runtime.html) or
/// [Builder](../tokio/runtime/struct.Builder.html) directly.
///
/// Note: This macro is designed to be simplistic and targets applications that
/// do not require a complex setup. If the provided functionality is not
/// sufficient, you may be interested in using
/// [Builder](../tokio/runtime/struct.Builder.html), which provides a more
/// powerful interface.
///
/// # Multi-threaded runtime
///
/// To use the multi-threaded runtime, the macro can be configured using
///
/// ```no_run
/// #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// The `worker_threads` option configures the number of worker threads, and
/// defaults to the number of cpus on the system.
///
/// Note: The multi-threaded runtime requires the `rt-multi-thread` feature
/// flag.
///
/// # Current thread runtime
///
/// The default test runtime is single-threaded. Each test gets a
/// separate current-thread runtime.
///
/// ```no_run
/// #[tokio::test]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// ## Usage
///
/// ### Set the name of the runtime
///
/// ```no_run
/// #[tokio::test(name = "my-test-runtime")]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// Equivalent code not using `#[tokio::test]`
///
/// ```no_run
/// #[test]
/// fn my_test() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .name("my-test-runtime")
///         .build()
///         .unwrap()
///         .block_on(async {
///             assert!(true);
///         })
/// }
/// ```
///
/// ### Using the multi-thread runtime
///
/// ```no_run
/// #[tokio::test(flavor = "multi_thread")]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// Equivalent code not using `#[tokio::test]`
///
/// ```no_run
/// #[test]
/// fn my_test() {
///     tokio::runtime::Builder::new_multi_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             assert!(true);
///         })
/// }
/// ```
///
/// ### Using current thread runtime
///
/// ```no_run
/// #[tokio::test]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// Equivalent code not using `#[tokio::test]`
///
/// ```no_run
/// #[test]
/// fn my_test() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             assert!(true);
///         })
/// }
/// ```
///
/// ### Set number of worker threads
///
/// ```no_run
/// #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// Equivalent code not using `#[tokio::test]`
///
/// ```no_run
/// #[test]
/// fn my_test() {
///     tokio::runtime::Builder::new_multi_thread()
///         .worker_threads(2)
///         .enable_all()
///         .build()
///         .unwrap()
///         .block_on(async {
///             assert!(true);
///         })
/// }
/// ```
///
/// ### Configure the runtime to start with time paused
///
/// ```no_run
/// #[tokio::test(start_paused = true)]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
///
/// Equivalent code not using `#[tokio::test]`
///
/// ```no_run
/// #[test]
/// fn my_test() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .start_paused(true)
///         .build()
///         .unwrap()
///         .block_on(async {
///             assert!(true);
///         })
/// }
/// ```
///
/// Note that `start_paused` requires the `test-util` feature to be enabled.
///
/// ### Rename package
///
/// ```rust
/// use tokio as tokio1;
///
/// #[tokio1::test(crate = "tokio1")]
/// async fn my_test() {
///     println!("Hello world");
/// }
/// ```
///
/// ### Configure unhandled panic behavior
///
/// Available options are `shutdown_runtime` and `ignore`. For more details, see
/// [`Builder::unhandled_panic`].
///
/// This option is only compatible with the `current_thread` runtime.
///
/// ```no_run
/// #[cfg(tokio_unstable)]
/// #[tokio::test(flavor = "current_thread", unhandled_panic = "shutdown_runtime")]
/// async fn my_test() {
///     let _ = tokio::spawn(async {
///         panic!("This panic will shutdown the runtime.");
///     }).await;
/// }
///
/// # fn main() { }
/// ```
///
/// Equivalent code not using `#[tokio::test]`
///
/// ```no_run
/// #[cfg(tokio_unstable)]
/// #[test]
/// fn my_test() {
///     tokio::runtime::Builder::new_current_thread()
///         .enable_all()
///         .unhandled_panic(UnhandledPanic::ShutdownRuntime)
///         .build()
///         .unwrap()
///         .block_on(async {
///             let _ = tokio::spawn(async {
///                 panic!("This panic will shutdown the runtime.");
///             }).await;
///         })
/// }
///
/// # fn main() { }
/// ```
///
/// **Note**: This option depends on Tokio's [unstable API][unstable]. See [the
/// documentation on unstable features][unstable] for details on how to enable
/// Tokio's unstable features.
///
/// [`Builder::unhandled_panic`]: ../tokio/runtime/struct.Builder.html#method.unhandled_panic
/// [unstable]: ../tokio/index.html#unstable-features
#[proc_macro_attribute]
pub fn test(args: TokenStream, item: TokenStream) -> TokenStream {
    entry::test(args.into(), item.into(), true).into()
}

/// Marks async function to be executed by runtime, suitable to test environment
///
/// ## Usage
///
/// ```no_run
/// #[tokio::test]
/// async fn my_test() {
///     assert!(true);
/// }
/// ```
#[proc_macro_attribute]
pub fn test_rt(args: TokenStream, item: TokenStream) -> TokenStream {
    entry::test(args.into(), item.into(), false).into()
}

/// Always fails with the error message below.
/// ```text
/// The #[tokio::main] macro requires rt or rt-multi-thread.
/// ```
#[proc_macro_attribute]
pub fn main_fail(_args: TokenStream, _item: TokenStream) -> TokenStream {
    syn::Error::new(
        proc_macro2::Span::call_site(),
        "The #[tokio::main] macro requires rt or rt-multi-thread.",
    )
    .to_compile_error()
    .into()
}

/// Always fails with the error message below.
/// ```text
/// The #[tokio::test] macro requires rt or rt-multi-thread.
/// ```
#[proc_macro_attribute]
pub fn test_fail(_args: TokenStream, _item: TokenStream) -> TokenStream {
    syn::Error::new(
        proc_macro2::Span::call_site(),
        "The #[tokio::test] macro requires rt or rt-multi-thread.",
    )
    .to_compile_error()
    .into()
}

/// Implementation detail of the `select!` macro. This macro is **not** intended
/// to be used as part of the public API and is permitted to change.
#[proc_macro]
#[doc(hidden)]
pub fn select_priv_declare_output_enum(input: TokenStream) -> TokenStream {
    select::declare_output_enum(input)
}

/// Implementation detail of the `select!` macro. This macro is **not** intended
/// to be used as part of the public API and is permitted to change.
#[proc_macro]
#[doc(hidden)]
pub fn select_priv_clean_pattern(input: TokenStream) -> TokenStream {
    select::clean_pattern_macro(input)
}