Make Serializer a trait, so anyone can implement it

examples/dialogue_bot_redis/src/main.rs

@@ -23,7 +23,7 @@ use serde::{Deserialize, Serialize};
 use std::sync::Arc;
 
 use teloxide::{
-    dispatching::dialogue::{RedisStorage, Serializer, Storage},
+    dispatching::dialogue::{serializer::Bincode, RedisStorage, Storage},
     prelude::*,
     types::{KeyboardButton, ReplyKeyboardMarkup},
 };
@@ -94,7 +94,7 @@ enum Dialogue {
 type Cx<State> = DialogueDispatcherHandlerCx<
     Message,
     State,
-    <RedisStorage as Storage<Dialogue>>::Error,
+    <RedisStorage<Bincode> as Storage<Dialogue>>::Error,
 >;
 type Res = ResponseResult<DialogueStage<Dialogue>>;
 
@@ -202,7 +202,7 @@ async fn run() {
                 // All serializer but JSON require enabling feature
                 // "serializer-<name>", e. g. "serializer-cbor"
                 // or "serializer-bincode"
-                RedisStorage::open("redis://127.0.0.1:6379", Serializer::Bincode)
+                RedisStorage::open("redis://127.0.0.1:6379", Bincode)
                     .await
                     .unwrap(),
             ),

src/dispatching/dialogue/mod.rs

@@ -56,4 +56,4 @@ pub use dialogue_stage::{exit, next, DialogueStage};
 pub use get_chat_id::GetChatId;
 #[cfg(feature = "redis-storage")]
 pub use storage::RedisStorage;
-pub use storage::{InMemStorage, Serializer, Storage};
+pub use storage::{serializer, InMemStorage, Serializer, Storage};

src/dispatching/dialogue/storage/redis_storage.rs

@@ -1,34 +1,37 @@
-use super::{
-    serializer::{self, Serializer},
-    Storage,
-};
+use super::{serializer::Serializer, Storage};
 use futures::future::BoxFuture;
 use redis::{AsyncCommands, FromRedisValue, IntoConnectionInfo};
 use serde::{de::DeserializeOwned, Serialize};
-use std::{ops::DerefMut, sync::Arc};
+use std::{
+    convert::Infallible,
+    fmt::{Debug, Display},
+    ops::DerefMut,
+    sync::Arc,
+};
 use thiserror::Error;
 use tokio::sync::Mutex;
 
 #[derive(Debug, Error)]
-pub enum Error {
-    #[error("{0}")]
-    SerdeError(#[from] serializer::Error),
+pub enum Error<SE>
+where
+    SE: Debug + Display,
+{
+    #[error("parsing/serializing error: {0}")]
+    SerdeError(SE),
     #[error("error from Redis: {0}")]
     RedisError(#[from] redis::RedisError),
 }
 
-type Result<T, E = Error> = std::result::Result<T, E>;
-
-pub struct RedisStorage {
+pub struct RedisStorage<S> {
     conn: Mutex<redis::aio::Connection>,
-    serializer: Serializer,
+    serializer: S,
 }
 
-impl RedisStorage {
+impl<S> RedisStorage<S> {
     pub async fn open(
         url: impl IntoConnectionInfo,
-        serializer: Serializer,
-    ) -> Result<Self> {
+        serializer: S,
+    ) -> Result<Self, Error<Infallible>> {
         Ok(Self {
             conn: Mutex::new(
                 redis::Client::open(url)?.get_async_connection().await?,
@@ -38,36 +41,42 @@ impl RedisStorage {
     }
 }
 
-impl<D> Storage<D> for RedisStorage
+impl<S, D> Storage<D> for RedisStorage<S>
 where
+    S: Send + Sync + Serializer<D> + 'static,
     D: Send + Serialize + DeserializeOwned + 'static,
+    <S as Serializer<D>>::Error: Debug + Display,
 {
-    type Error = Error;
+    type Error = Error<<S as Serializer<D>>::Error>;
 
     // `.del().ignore()` is much more readable than `.del()\n.ignore()`
     #[rustfmt::skip]
     fn remove_dialogue(
         self: Arc<Self>,
         chat_id: i64,
-    ) -> BoxFuture<'static, Result<Option<D>>> {
+    ) -> BoxFuture<'static, Result<Option<D>, Self::Error>> {
         Box::pin(async move {
             let res = redis::pipe()
                 .atomic()
                 .get(chat_id)
                 .del(chat_id).ignore()
-                .query_async::<_, redis::Value>(self.conn.lock().await.deref_mut())
+                .query_async::<_, redis::Value>(
+                    self.conn.lock().await.deref_mut(),
+                )
                 .await?;
-            // We're expecting `.pipe()` to return us an exactly one result in bulk,
-            // so all other branches should be unreachable
+            // We're expecting `.pipe()` to return us an exactly one result in
+            // bulk, so all other branches should be unreachable
             match res {
                 redis::Value::Bulk(bulk) if bulk.len() == 1 => {
-                    Ok(
-                        Option::<Vec<u8>>::from_redis_value(&bulk[0])?
-                            .map(|v| self.serializer.deserialize(&v))
-                            .transpose()?
-                    )
-                },
-                _ => unreachable!()
+                    Ok(Option::<Vec<u8>>::from_redis_value(&bulk[0])?
+                        .map(|v| {
+                            self.serializer
+                                .deserialize(&v)
+                                .map_err(Error::SerdeError)
+                        })
+                        .transpose()?)
+                }
+                _ => unreachable!(),
             }
         })
     }
@@ -76,16 +85,21 @@ where
         self: Arc<Self>,
         chat_id: i64,
         dialogue: D,
-    ) -> BoxFuture<'static, Result<Option<D>>> {
+    ) -> BoxFuture<'static, Result<Option<D>, Self::Error>> {
         Box::pin(async move {
-            let dialogue = self.serializer.serialize(&dialogue)?;
+            let dialogue = self
+                .serializer
+                .serialize(&dialogue)
+                .map_err(Error::SerdeError)?;
             Ok(self
                 .conn
                 .lock()
                 .await
                 .getset::<_, Vec<u8>, Option<Vec<u8>>>(chat_id, dialogue)
                 .await?
-                .map(|d| self.serializer.deserialize(&d))
+                .map(|d| {
+                    self.serializer.deserialize(&d).map_err(Error::SerdeError)
+                })
                 .transpose()?)
         })
     }

src/dispatching/dialogue/storage/serializer.rs

@@ -1,53 +1,63 @@
 use serde::{de::DeserializeOwned, ser::Serialize};
-use thiserror::Error;
-use Serializer::*;
 
-#[derive(Debug, Error)]
-pub enum Error {
-    #[error("failed parsing/serializing JSON: {0}")]
-    JSONError(#[from] serde_json::Error),
-    #[cfg(feature = "cbor-serializer")]
-    #[error("failed parsing/serializing CBOR: {0}")]
-    CBORError(#[from] serde_cbor::Error),
-    #[cfg(feature = "bincode-serializer")]
-    #[error("failed parsing/serializing Bincode: {0}")]
-    BincodeError(#[from] bincode::Error),
+pub trait Serializer<D> {
+    type Error;
+
+    fn serialize(&self, val: &D) -> Result<Vec<u8>, Self::Error>;
+    fn deserialize(&self, data: &[u8]) -> Result<D, Self::Error>;
 }
 
-type Result<T, E = Error> = std::result::Result<T, E>;
+pub struct JSON;
 
-pub enum Serializer {
-    JSON,
-    #[cfg(feature = "cbor-serializer")]
-    CBOR,
-    #[cfg(feature = "bincode-serializer")]
-    Bincode,
-}
+impl<D> Serializer<D> for JSON
+where
+    D: Serialize + DeserializeOwned,
+{
+    type Error = serde_json::Error;
 
-impl Serializer {
-    pub fn serialize<D>(&self, val: &D) -> Result<Vec<u8>>
-    where
-        D: Serialize,
-    {
-        Ok(match self {
-            JSON => serde_json::to_vec(val)?,
-            #[cfg(feature = "cbor-serializer")]
-            CBOR => serde_cbor::to_vec(val)?,
-            #[cfg(feature = "bincode-serializer")]
-            Bincode => bincode::serialize(val)?,
-        })
+    fn serialize(&self, val: &D) -> Result<Vec<u8>, Self::Error> {
+        serde_json::to_vec(val)
     }
 
-    pub fn deserialize<'de, D>(&self, data: &'de [u8]) -> Result<D>
-    where
-        D: DeserializeOwned,
-    {
-        Ok(match self {
-            JSON => serde_json::from_slice(data)?,
-            #[cfg(feature = "cbor-serializer")]
-            CBOR => serde_cbor::from_slice(data)?,
-            #[cfg(feature = "bincode-serializer")]
-            Bincode => bincode::deserialize(data)?,
-        })
+    fn deserialize(&self, data: &[u8]) -> Result<D, Self::Error> {
+        serde_json::from_slice(data)
+    }
+}
+
+#[cfg(feature = "cbor-serializer")]
+pub struct CBOR;
+
+#[cfg(feature = "cbor-serializer")]
+impl<D> Serializer<D> for CBOR
+where
+    D: Serialize + DeserializeOwned,
+{
+    type Error = serde_cbor::Error;
+
+    fn serialize(&self, val: &D) -> Result<Vec<u8>, Self::Error> {
+        serde_cbor::to_vec(val)
+    }
+
+    fn deserialize(&self, data: &[u8]) -> Result<D, Self::Error> {
+        serde_cbor::from_slice(data)
+    }
+}
+
+#[cfg(feature = "bincode-serializer")]
+pub struct Bincode;
+
+#[cfg(feature = "bincode-serializer")]
+impl<D> Serializer<D> for Bincode
+where
+    D: Serialize + DeserializeOwned,
+{
+    type Error = bincode::Error;
+
+    fn serialize(&self, val: &D) -> Result<Vec<u8>, Self::Error> {
+        bincode::serialize(val)
+    }
+
+    fn deserialize(&self, data: &[u8]) -> Result<D, Self::Error> {
+        bincode::deserialize(data)
     }
 }