Future-proof enums with a __Nonexhaustive variant.

This can be replaced with the #[non_exhaustive] compiler attribute once
it's stabilized.

src/call.rs

@@ -30,6 +30,12 @@ pub enum SessionDescriptionType {
     /// An offer.
     #[serde(rename = "offer")]
     Offer,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/call/hangup.rs

@@ -35,6 +35,12 @@ pub enum Reason {
     /// Party did not answer in time.
     #[serde(rename = "invite_timeout")]
     InviteTimeout,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/collections/all.rs

@@ -603,6 +603,9 @@ impl<'de> Deserialize<'de> for Event {
                     Ok(Event::Custom(event))
                 }
             }
+            EventType::__Nonexhaustive => {
+                panic!("__Nonexhaustive enum variant is not intended for use.")
+            }
         }
     }
 }
@@ -868,6 +871,9 @@ impl<'de> Deserialize<'de> for RoomEvent {
             | EventType::Receipt
             | EventType::Tag
             | EventType::Typing => Err(D::Error::custom("not a room event".to_string())),
+            EventType::__Nonexhaustive => {
+                panic!("__Nonexhaustive enum variant is not intended for use.")
+            }
         }
     }
 }
@@ -1059,6 +1065,9 @@ impl<'de> Deserialize<'de> for StateEvent {
             | EventType::Sticker
             | EventType::Tag
             | EventType::Typing => Err(D::Error::custom("not a state event".to_string())),
+            EventType::__Nonexhaustive => {
+                panic!("__Nonexhaustive enum variant is not intended for use.")
+            }
         }
     }
 }

src/collections/only.rs

@@ -209,6 +209,9 @@ impl<'de> Deserialize<'de> for Event {
             | EventType::Sticker => Err(D::Error::custom(
                 "not exclusively a basic event".to_string(),
             )),
+            EventType::__Nonexhaustive => {
+                panic!("__Nonexhaustive enum variant is not intended for use.")
+            }
         }
     }
 }
@@ -346,6 +349,9 @@ impl<'de> Deserialize<'de> for RoomEvent {
             | EventType::Typing => {
                 Err(D::Error::custom("not exclusively a room event".to_string()))
             }
+            EventType::__Nonexhaustive => {
+                panic!("__Nonexhaustive enum variant is not intended for use.")
+            }
         }
     }
 }

src/lib.rs

@@ -227,6 +227,11 @@ pub enum EventType {
 
     /// Any event that is not part of the specification.
     Custom(String),
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    __Nonexhaustive,
 }
 
 /// A basic event.
@@ -324,6 +329,9 @@ impl Display for EventType {
             EventType::Tag => "m.tag",
             EventType::Typing => "m.typing",
             EventType::Custom(ref event_type) => event_type,
+            EventType::__Nonexhaustive => {
+                panic!("__Nonexhaustive enum variant is not intended for use.")
+            }
         };
 
         write!(f, "{}", event_type_str)

src/macros.rs

@@ -4,6 +4,7 @@ macro_rules! impl_enum {
             fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> Result<(), ::std::fmt::Error> {
                 let variant = match *self {
                     $($name::$variant => $s,)*
+                    $name::__Nonexhaustive => panic!("__Nonexhaustive enum variant is not intended for use."),
                 };
 
                 write!(f, "{}", variant)

src/presence.rs

@@ -53,6 +53,12 @@ pub enum PresenceState {
     /// Connected to the service but not available for chat.
     #[serde(rename = "unavailable")]
     Unavailable,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/room/guest_access.rs

@@ -27,6 +27,12 @@ pub enum GuestAccess {
     /// Guests are not allowed to join the room.
     #[serde(rename = "forbidden")]
     Forbidden,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/room/history_visibility.rs

@@ -39,6 +39,12 @@ pub enum HistoryVisibility {
     /// participating homeserver with anyone, regardless of whether they have ever joined the room.
     #[serde(rename = "world_readable")]
     WorldReadable,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/room/join_rules.rs

@@ -33,6 +33,12 @@ pub enum JoinRule {
     /// Anyone can join the room without any prior action.
     #[serde(rename = "public")]
     Public,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/room/member.rs

@@ -80,6 +80,12 @@ pub enum MembershipState {
     /// The user has left.
     #[serde(rename = "leave")]
     Leave,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {

src/room/message.rs

@@ -51,6 +51,12 @@ pub enum MessageType {
     /// A video message.
     #[serde(rename = "m.video")]
     Video,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 /// The payload of a message event.
@@ -536,6 +542,9 @@ impl<'de> Deserialize<'de> for MessageEventContent {
 
                 Ok(MessageEventContent::Video(content))
             }
+            MessageType::__Nonexhaustive => Err(D::Error::custom(
+                "Attempted to deserialize __Nonexhaustive variant.",
+            )),
         }
     }
 }

src/room/message/feedback.rs

@@ -32,6 +32,12 @@ pub enum FeedbackType {
     /// Sent when a message has been observed by the end user.
     #[serde(rename = "read")]
     Read,
+
+    /// Additional variants may be added in the future and will not be considered breaking changes
+    /// to `ruma-events`.
+    #[doc(hidden)]
+    #[serde(skip)]
+    __Nonexhaustive,
 }
 
 impl_enum! {