Simplify deserialization

src/event_id.rs

@@ -8,7 +8,7 @@ use std::{
 #[cfg(feature = "diesel")]
 use diesel::sql_types::Text;
 use serde::{
-    de::{Error as SerdeError, Unexpected, Visitor},
+    de::{Error as SerdeError, Expected, Unexpected},
     Deserialize, Deserializer, Serialize, Serializer,
 };
 use url::Host;
@@ -75,9 +75,6 @@ struct Original {
     pub port: u16,
 }
 
-/// A serde visitor for `EventId`.
-struct EventIdVisitor;
-
 impl EventId {
     /// Attempts to generate an `EventId` for the given origin server with a localpart consisting
     /// of 18 random ASCII characters. This should only be used for events in the original format
@@ -158,7 +155,10 @@ impl<'de> Deserialize<'de> for EventId {
     where
         D: Deserializer<'de>,
     {
-        deserializer.deserialize_any(EventIdVisitor)
+        String::deserialize(deserializer).and_then(|v| {
+            EventId::try_from(&v as &str)
+                .map_err(|_| SerdeError::invalid_value(Unexpected::Str(&v), &ExpectedEventId))
+        })
     }
 }
 
@@ -189,22 +189,12 @@ impl<'a> TryFrom<&'a str> for EventId {
     }
 }
 
-impl<'de> Visitor<'de> for EventIdVisitor {
-    type Value = EventId;
+struct ExpectedEventId;
 
-    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+impl Expected for ExpectedEventId {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> FmtResult {
         write!(formatter, "a Matrix event ID as a string")
     }
-
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-    where
-        E: SerdeError,
-    {
-        match EventId::try_from(v) {
-            Ok(event_id) => Ok(event_id),
-            Err(_) => Err(SerdeError::invalid_value(Unexpected::Str(v), &self)),
-        }
-    }
 }
 
 #[cfg(test)]

src/room_alias_id.rs

@@ -8,7 +8,7 @@ use std::{
 #[cfg(feature = "diesel")]
 use diesel::sql_types::Text;
 use serde::{
-    de::{Error as SerdeError, Unexpected, Visitor},
+    de::{Error as SerdeError, Expected, Unexpected},
     Deserialize, Deserializer, Serialize, Serializer,
 };
 use url::Host;
@@ -40,9 +40,6 @@ pub struct RoomAliasId {
     port: u16,
 }
 
-/// A serde visitor for `RoomAliasId`.
-struct RoomAliasIdVisitor;
-
 impl RoomAliasId {
     /// Returns a `Host` for the room alias ID, containing the server name (minus the port) of
     /// the originating homeserver.
@@ -83,7 +80,10 @@ impl<'de> Deserialize<'de> for RoomAliasId {
     where
         D: Deserializer<'de>,
     {
-        deserializer.deserialize_any(RoomAliasIdVisitor)
+        String::deserialize(deserializer).and_then(|v| {
+            RoomAliasId::try_from(&v as &str)
+                .map_err(|_| SerdeError::invalid_value(Unexpected::Str(&v), &ExpectedRoomAliasId))
+        })
     }
 }
 
@@ -105,22 +105,12 @@ impl<'a> TryFrom<&'a str> for RoomAliasId {
     }
 }
 
-impl<'de> Visitor<'de> for RoomAliasIdVisitor {
-    type Value = RoomAliasId;
+struct ExpectedRoomAliasId;
 
-    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+impl Expected for ExpectedRoomAliasId {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> FmtResult {
         write!(formatter, "a Matrix room alias ID as a string")
     }
-
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-    where
-        E: SerdeError,
-    {
-        match RoomAliasId::try_from(v) {
-            Ok(room_alias_id) => Ok(room_alias_id),
-            Err(_) => Err(SerdeError::invalid_value(Unexpected::Str(v), &self)),
-        }
-    }
 }
 
 #[cfg(test)]

src/room_id.rs

@@ -8,7 +8,7 @@ use std::{
 #[cfg(feature = "diesel")]
 use diesel::sql_types::Text;
 use serde::{
-    de::{Error as SerdeError, Unexpected, Visitor},
+    de::{Error as SerdeError, Expected, Unexpected},
     Deserialize, Deserializer, Serialize, Serializer,
 };
 use url::Host;
@@ -40,9 +40,6 @@ pub struct RoomId {
     port: u16,
 }
 
-/// A serde visitor for `RoomId`.
-struct RoomIdVisitor;
-
 impl RoomId {
     /// Attempts to generate a `RoomId` for the given origin server with a localpart consisting of
     /// 18 random ASCII characters.
@@ -98,7 +95,10 @@ impl<'de> Deserialize<'de> for RoomId {
     where
         D: Deserializer<'de>,
     {
-        deserializer.deserialize_any(RoomIdVisitor)
+        String::deserialize(deserializer).and_then(|v| {
+            RoomId::try_from(&v as &str)
+                .map_err(|_| SerdeError::invalid_value(Unexpected::Str(&v), &ExpectedRoomId))
+        })
     }
 }
 
@@ -120,22 +120,12 @@ impl<'a> TryFrom<&'a str> for RoomId {
     }
 }
 
-impl<'de> Visitor<'de> for RoomIdVisitor {
-    type Value = RoomId;
+struct ExpectedRoomId;
 
-    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+impl Expected for ExpectedRoomId {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> FmtResult {
         write!(formatter, "a Matrix room ID as a string")
     }
-
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-    where
-        E: SerdeError,
-    {
-        match RoomId::try_from(v) {
-            Ok(room_id) => Ok(room_id),
-            Err(_) => Err(SerdeError::invalid_value(Unexpected::Str(v), &self)),
-        }
-    }
 }
 
 #[cfg(test)]

src/room_id_or_room_alias_id.rs

@@ -8,7 +8,7 @@ use std::{
 #[cfg(feature = "diesel")]
 use diesel::sql_types::Text;
 use serde::{
-    de::{Error as SerdeError, Unexpected, Visitor},
+    de::{Error as SerdeError, Expected, Unexpected},
     Deserialize, Deserializer, Serialize, Serializer,
 };
 
@@ -43,9 +43,6 @@ pub enum RoomIdOrAliasId {
     RoomId(RoomId),
 }
 
-/// A serde visitor for `RoomIdOrAliasId`.
-struct RoomIdOrAliasIdVisitor;
-
 impl Display for RoomIdOrAliasId {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
         match *self {
@@ -86,7 +83,11 @@ impl<'de> Deserialize<'de> for RoomIdOrAliasId {
     where
         D: Deserializer<'de>,
     {
-        deserializer.deserialize_any(RoomIdOrAliasIdVisitor)
+        String::deserialize(deserializer).and_then(|v| {
+            RoomIdOrAliasId::try_from(&v as &str).map_err(|_| {
+                SerdeError::invalid_value(Unexpected::Str(&v), &ExpectedRoomIdOrAliasId)
+            })
+        })
     }
 }
 
@@ -119,22 +120,12 @@ impl<'a> TryFrom<&'a str> for RoomIdOrAliasId {
     }
 }
 
-impl<'de> Visitor<'de> for RoomIdOrAliasIdVisitor {
-    type Value = RoomIdOrAliasId;
+struct ExpectedRoomIdOrAliasId;
 
-    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+impl Expected for ExpectedRoomIdOrAliasId {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> FmtResult {
         write!(formatter, "a Matrix room ID or room alias ID as a string")
     }
-
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-    where
-        E: SerdeError,
-    {
-        match RoomIdOrAliasId::try_from(v) {
-            Ok(room_id_or_alias_id) => Ok(room_id_or_alias_id),
-            Err(_) => Err(SerdeError::invalid_value(Unexpected::Str(v), &self)),
-        }
-    }
 }
 
 #[cfg(test)]

src/room_version_id.rs

@@ -8,7 +8,7 @@ use std::{
 #[cfg(feature = "diesel")]
 use diesel::sql_types::Text;
 use serde::{
-    de::{Error as SerdeError, Unexpected, Visitor},
+    de::{Error as SerdeError, Expected, Unexpected},
     Deserialize, Deserializer, Serialize, Serializer,
 };
 
@@ -55,9 +55,6 @@ enum InnerRoomVersionId {
     Custom(String),
 }
 
-/// A serde visitor for `RoomVersionId`.
-struct RoomVersionIdVisitor;
-
 impl RoomVersionId {
     /// Creates a version 1 room ID.
     pub fn version_1() -> Self {
@@ -157,7 +154,10 @@ impl<'de> Deserialize<'de> for RoomVersionId {
     where
         D: Deserializer<'de>,
     {
-        deserializer.deserialize_any(RoomVersionIdVisitor)
+        String::deserialize(deserializer).and_then(|v| {
+            RoomVersionId::try_from(&v as &str)
+                .map_err(|_| SerdeError::invalid_value(Unexpected::Str(&v), &ExpectedRoomVersionId))
+        })
     }
 }
 
@@ -187,22 +187,12 @@ impl<'a> TryFrom<&'a str> for RoomVersionId {
     }
 }
 
-impl<'de> Visitor<'de> for RoomVersionIdVisitor {
-    type Value = RoomVersionId;
+struct ExpectedRoomVersionId;
 
-    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+impl Expected for ExpectedRoomVersionId {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> FmtResult {
         write!(formatter, "a Matrix room version ID as a string")
     }
-
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-    where
-        E: SerdeError,
-    {
-        match RoomVersionId::try_from(v) {
-            Ok(room_id) => Ok(room_id),
-            Err(_) => Err(SerdeError::invalid_value(Unexpected::Str(v), &self)),
-        }
-    }
 }
 
 #[cfg(test)]

src/user_id.rs

@@ -8,7 +8,7 @@ use std::{
 #[cfg(feature = "diesel")]
 use diesel::sql_types::Text;
 use serde::{
-    de::{Error as SerdeError, Unexpected, Visitor},
+    de::{Error as SerdeError, Expected, Unexpected},
     Deserialize, Deserializer, Serialize, Serializer,
 };
 use url::Host;
@@ -40,9 +40,6 @@ pub struct UserId {
     port: u16,
 }
 
-/// A serde visitor for `UserId`.
-struct UserIdVisitor;
-
 impl UserId {
     /// Attempts to generate a `UserId` for the given origin server with a localpart consisting of
     /// 12 random ASCII characters.
@@ -102,7 +99,10 @@ impl<'de> Deserialize<'de> for UserId {
     where
         D: Deserializer<'de>,
     {
-        deserializer.deserialize_any(UserIdVisitor)
+        String::deserialize(deserializer).and_then(|v| {
+            UserId::try_from(&v as &str)
+                .map_err(|_| SerdeError::invalid_value(Unexpected::Str(&v), &ExpectedUserId))
+        })
     }
 }
 
@@ -133,22 +133,12 @@ impl<'a> TryFrom<&'a str> for UserId {
     }
 }
 
-impl<'de> Visitor<'de> for UserIdVisitor {
-    type Value = UserId;
+struct ExpectedUserId;
 
-    fn expecting(&self, formatter: &mut Formatter<'_>) -> FmtResult {
+impl Expected for ExpectedUserId {
+    fn fmt(&self, formatter: &mut Formatter<'_>) -> FmtResult {
         write!(formatter, "a Matrix user ID as a string")
     }
-
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-    where
-        E: SerdeError,
-    {
-        match UserId::try_from(v) {
-            Ok(user_id) => Ok(user_id),
-            Err(_) => Err(SerdeError::invalid_value(Unexpected::Str(v), &self)),
-        }
-    }
 }
 
 #[cfg(test)]