Merge pull request #77 from telebofr/add_ignore_error_policies

Add `Ignore` and `IgnoreSafe` error policies.

Cargo.toml

@@ -22,3 +22,4 @@ thiserror = "1.0.2"
 default = []
 
 unstable-stream = [] # add streams to public API
+never-type = [] # add never type (`!`) to punlic API

src/dispatching/dispatchers/filter/error_policy.rs

@@ -1,7 +1,10 @@
-use std::future::Future;
+use std::{
+    pin::Pin,
+    future::Future,
+    convert::Infallible,
+};
 
 use async_trait::async_trait;
-use std::pin::Pin;
 
 /// Implementors of this trait are treated as error-handlers.
 #[async_trait]
@@ -11,6 +14,113 @@ pub trait ErrorPolicy<E> {
         E: 'async_trait;
 }
 
+/// Error policy that silently ignores all errors
+///
+/// ## Example
+/// ```
+/// # #[tokio::main]
+/// # async fn main() {
+/// use telebofr::dispatching::dispatchers::filter::error_policy::{
+///     ErrorPolicy,
+///     Ignore,
+/// };
+///
+/// Ignore.handle_error(()).await;
+/// Ignore.handle_error(404).await;
+/// Ignore.handle_error(String::from("error")).await;
+/// # }
+/// ```
+pub struct Ignore;
+
+#[async_trait]
+impl<E> ErrorPolicy<E> for Ignore
+where
+    E: Send,
+{
+    async fn handle_error(&self, _: E)
+    where
+        E: 'async_trait
+    {}
+}
+
+/// Error policy that silently ignores all errors that can never happen (e.g.: [`!`] or [`Infallible`])
+///
+/// ## Examples
+/// ```
+/// # #[tokio::main]
+/// # async fn main() {
+/// use std::convert::{TryInto, Infallible};
+///
+/// use telebofr::dispatching::dispatchers::filter::error_policy::{
+///     ErrorPolicy,
+///     IgnoreSafe,
+/// };
+///
+/// let result: Result<String, Infallible> = "str".try_into();
+/// match result {
+///     Ok(string) => println!("{}", string),
+///     Err(inf) => IgnoreSafe.handle_error(inf).await,
+/// }
+///
+/// IgnoreSafe.handle_error(return).await; // return type of `return` is `!` (aka never)
+/// # }
+/// ```
+///
+/// ```compile_fail
+/// use telebofr::dispatching::dispatchers::filter::error_policy::{
+///     ErrorPolicy,
+///     IgnoreSafe,
+/// };
+///
+/// IgnoreSafe.handle_error(0);
+/// ```
+///
+/// ## Note
+/// Never type is not stabilized yet (see [`#35121`]) so all API that uses [`!`]
+/// (including `impl ErrorPolicy<!> for IgnoreSafe`) we hide under the
+/// `never-type` cargo feature.
+///
+/// [`!`]: https://doc.rust-lang.org/std/primitive.never.html
+/// [`Infallible`]: std::convert::Infallible
+/// [`#35121`]: https://github.com/rust-lang/rust/issues/35121
+pub struct IgnoreSafe;
+
+#[cfg(feature = "never-type")]
+#[async_trait]
+impl ErrorPolicy<!> for IgnoreSafe {
+    async fn handle_error(&self, never: !)
+    where
+        !: 'async_trait
+    {
+        never
+    }
+}
+
+#[async_trait]
+impl ErrorPolicy<Infallible> for IgnoreSafe {
+    async fn handle_error(&self, inf: Infallible)
+    where
+        Infallible: 'async_trait
+    {
+        match inf {}
+    }
+}
+
+/// Implementation of `ErrorPolicy` for `async fn`s
+///
+/// ## Example
+/// ```
+/// # #[tokio::main]
+/// # async fn main() {
+/// use telebofr::dispatching::dispatchers::filter::error_policy::ErrorPolicy;
+///
+/// let closure = |e: i32| async move {
+///     eprintln!("Error code{}", e)
+/// };
+///
+/// closure.handle_error(404).await;
+/// # }
+/// ```
 impl<E, F, Fut> ErrorPolicy<E> for F
 where
     F: Fn(E) -> Fut + Sync,

src/lib.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "never-type", feature(never_type))]
+
 #[macro_use]
 extern crate derive_more;
 #[macro_use]