Merge pull request #78 from telebofr/error_policy

Error policy

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

@@ -1,32 +1,138 @@
-use std::{fmt::Debug, future::Future, pin::Pin};
+use std::{
+    pin::Pin,
+    future::Future,
+    convert::Infallible,
+};
 
-// TODO: shouldn't it be trait?
-pub enum ErrorPolicy<'a, E> {
-    Ignore,
-    Log,
-    Custom(Box<dyn Fn(E) -> Pin<Box<dyn Future<Output = ()> + 'a>>>),
-}
+use async_trait::async_trait;
 
-impl<'a, E> ErrorPolicy<'a, E>
-where
-    E: Debug,
-{
-    pub async fn handle_error(&self, error: E) {
-        match self {
-            Self::Ignore => {}
-            Self::Log => {
-                // TODO: better message
-                log::error!("Error in handler: {:?}", error)
-            }
-            Self::Custom(func) => func(error).await,
-        }
-    }
-
-    pub fn custom<F, Fut>(f: F) -> Self
+/// Implementors of this trait are treated as error-handlers.
+#[async_trait]
+pub trait ErrorPolicy<E> {
+    async fn handle_error(&self, error: E)
     where
-        F: Fn(E) -> Fut + 'static,
-        Fut: Future<Output = ()> + 'a,
+        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
     {
-        Self::Custom(Box::new(move |e| Box::pin(f(e))))
+        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,
+    Fut: Future<Output = ()> + Send,
+    E: Send,
+{
+    fn handle_error<'s, 'async_trait>(&'s self, error: E) -> Pin<Box<dyn Future<Output = ()> + Send + 'async_trait>>
+    where
+        's: 'async_trait,
+        Self: 'async_trait,
+        E: 'async_trait
+    {
+        Box::pin(async move { self(error).await })
     }
 }

src/dispatching/dispatchers/filter/mod.rs

@@ -32,11 +32,12 @@ type Handlers<'a, T, E> =
 ///
 /// Simplest example:
 /// ```no_run
-/// # use telebofr::Bot;
-/// use telebofr::types::Message;
-///  async fn run() {
+/// # async fn run() {
 /// use std::convert::Infallible;
+///
 /// use telebofr::{
+///     Bot,
+///     types::Message,
 ///     dispatching::{
 ///         dispatchers::filter::{error_policy::ErrorPolicy, FilterDispatcher},
 ///         updater::polling,
@@ -51,7 +52,7 @@ type Handlers<'a, T, E> =
 ///
 /// // create dispatching which handlers can't fail
 /// // with error policy that just ignores all errors (that can't ever happen)
-/// let mut dp = FilterDispatcher::<Infallible>::new(ErrorPolicy::Ignore)
+/// let mut dp = FilterDispatcher::<Infallible, _>::new(|_| async { () })
 ///     // Add 'handler' that will handle all messages sent to the bot
 ///     .message_handler(true, |mes: Message| {
 ///         async move { println!("New message: {:?}", mes) }
@@ -66,10 +67,9 @@ type Handlers<'a, T, E> =
 /// ```
 ///
 /// [`std::fmt::Debug`]: std::fmt::Debug
-/// [Custom error policy]:
-/// crate::dispatching::filter::error_policy::ErrorPolicy::Custom [updater]:
-/// crate::dispatching::updater
-pub struct FilterDispatcher<'a, E> {
+/// [Custom error policy]: crate::dispatching::filter::error_policy::ErrorPolicy::Custom
+/// [updater]: crate::dispatching::updater
+pub struct FilterDispatcher<'a, E, Ep> {
     message_handlers: Handlers<'a, Message, E>,
     edited_message_handlers: Handlers<'a, Message, E>,
     channel_post_handlers: Handlers<'a, Message, E>,
@@ -77,14 +77,15 @@ pub struct FilterDispatcher<'a, E> {
     inline_query_handlers: Handlers<'a, (), E>,
     chosen_inline_result_handlers: Handlers<'a, ChosenInlineResult, E>,
     callback_query_handlers: Handlers<'a, CallbackQuery, E>,
-    error_policy: ErrorPolicy<'a, E>,
+    error_policy: Ep,
 }
 
-impl<'a, E> FilterDispatcher<'a, E>
+impl<'a, E, Ep> FilterDispatcher<'a, E, Ep>
 where
+    Ep: ErrorPolicy<E>,
     E: std::fmt::Debug, // TODO: Is this really necessary?
 {
-    pub fn new(error_policy: ErrorPolicy<'a, E>) -> Self {
+    pub fn new(error_policy: Ep) -> Self {
         FilterDispatcher {
             message_handlers: Vec::new(),
             edited_message_handlers: Vec::new(),
@@ -183,7 +184,6 @@ where
         updates
             .for_each(|res| {
                 async {
-                    let res = res;
                     let Update { kind, id } = match res {
                         Ok(upd) => upd,
                         _ => return, // TODO: proper error handling
@@ -265,10 +265,11 @@ where
 }
 
 #[async_trait(? Send)]
-impl<'a, U, E> Dispatcher<'a, U> for FilterDispatcher<'a, E>
+impl<'a, U, E, Ep> Dispatcher<'a, U> for FilterDispatcher<'a, E, Ep>
 where
     E: std::fmt::Debug,
     U: Updater + 'a,
+    Ep: ErrorPolicy<E>,
 {
     async fn dispatch(&'a mut self, updater: U) {
         FilterDispatcher::dispatch(self, updater).await
@@ -286,9 +287,7 @@ mod tests {
 
     use crate::{
         dispatching::{
-            dispatchers::filter::{
-                error_policy::ErrorPolicy, FilterDispatcher,
-            },
+            dispatchers::filter::FilterDispatcher,
             updater::StreamUpdater,
         },
         types::{
@@ -302,7 +301,7 @@ mod tests {
         let counter = &AtomicI32::new(0);
         let counter2 = &AtomicI32::new(0);
 
-        let mut dp = FilterDispatcher::<Infallible>::new(ErrorPolicy::Ignore)
+        let mut dp = FilterDispatcher::<Infallible, _>::new(|_| async { () } )
             .message_handler(true, |_mes: Message| {
                 async move {
                     counter.fetch_add(1, Ordering::SeqCst);

src/lib.rs

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