Make room_id optional

This field can be absent in some contextes, notably in the responses
to the /sync endpoint, where the events are summarised in the initial
sync of a client.

Fixes #19

src/lib.rs

@@ -214,7 +214,10 @@ pub trait RoomEvent: Event {
     fn origin_server_ts(&self) -> u64;
 
     /// The unique identifier for the room associated with this event.
-    fn room_id(&self) -> &RoomId;
+    ///
+    /// This can be `None` if the event came from a context where there is
+    /// no ambiguity which room it belongs to, like a `/sync` response for example.
+    fn room_id(&self) -> Option<&RoomId>;
 
     /// The unique identifier for the user who sent this event.
     fn sender(&self) -> &UserId;

src/macros.rs

@@ -94,7 +94,8 @@ macro_rules! room_event {
             pub origin_server_ts: u64,
 
             /// The unique identifier for the room associated with this event.
-            pub room_id: ::ruma_identifiers::RoomId,
+            #[serde(skip_serializing_if="Option::is_none")]
+            pub room_id: Option<::ruma_identifiers::RoomId>,
 
             /// Additional key-value pairs not signed by the homeserver.
             #[serde(skip_serializing_if="Option::is_none")]
@@ -126,8 +127,8 @@ macro_rules! impl_room_event {
                 self.origin_server_ts
             }
 
-            fn room_id(&self) -> &::ruma_identifiers::RoomId {
-                &self.room_id
+            fn room_id(&self) -> Option<&::ruma_identifiers::RoomId> {
+                self.room_id.as_ref()
             }
 
             fn unsigned(&self) -> Option<&::serde_json::Value> {
@@ -172,7 +173,8 @@ macro_rules! state_event {
             pub prev_content: Option<$content_type>,
 
             /// The unique identifier for the room associated with this event.
-            pub room_id: ::ruma_identifiers::RoomId,
+            #[serde(skip_serializing_if="Option::is_none")]
+            pub room_id: Option<::ruma_identifiers::RoomId>,
 
             /// A key that determines which piece of room state the event represents.
             pub state_key: String,

src/receipt.rs

@@ -8,7 +8,11 @@ event! {
     /// Informs the client of new receipts.
     pub struct ReceiptEvent(ReceiptEventContent) {
         /// The unique identifier for the room associated with this event.
-        pub room_id: RoomId
+        ///
+        /// This can be `None` if the event came from a context where there is
+        /// no ambiguity which room it belongs to, like a `/sync` response for example.
+        #[serde(skip_serializing_if="Option::is_none")]
+        pub room_id: Option<RoomId>
     }
 }
 

src/room/pinned_events.rs

@@ -38,7 +38,7 @@ mod tests {
             event_type: EventType::RoomPinnedEvents,
             origin_server_ts: 1432804485886,
             prev_content: None,
-            room_id: RoomId::new("example.com").unwrap(),
+            room_id: Some(RoomId::new("example.com").unwrap()),
             sender: UserId::new("example.com").unwrap(),
             state_key: "".to_string(),
             unsigned: None,

src/typing.rs

@@ -6,7 +6,11 @@ event! {
     /// Informs the client of the list of users currently typing.
     pub struct TypingEvent(TypingEventContent) {
         /// The unique identifier for the room associated with this event.
-        pub room_id: RoomId
+        ///
+        /// This can be `None` if the event came from a context where there is
+        /// no ambiguity which room it belongs to, like a `/sync` response for example.
+        #[serde(skip_serializing_if="Option::is_none")]
+        pub room_id: Option<RoomId>
     }
 }