events: Support m.room.message events with custom msgtypes

ruma-events/src/room/message.rs

@@ -1,5 +1,7 @@
 //! Types for the *m.room.message* event.
 
+use std::collections::BTreeMap;
+
 use js_int::UInt;
 use ruma_events_macros::MessageEventContent;
 #[cfg(feature = "unstable-pre-spec")]
@@ -64,6 +66,10 @@ pub enum MessageEventContent {
     /// A request to initiate a key verification.
     #[cfg(feature = "unstable-pre-spec")]
     VerificationRequest(KeyVerificationRequestEventContent),
+
+    /// A custom message.
+    #[doc(hidden)]
+    _Custom(CustomEventContent),
 }
 
 /// Enum modeling the different ways relationships can be expressed in a
@@ -586,3 +592,15 @@ pub struct KeyVerificationRequestEventContent {
     /// events that have a m.reference relationship with this event.
     pub to: UserId,
 }
+
+/// The payload for a custom message event.
+#[doc(hidden)]
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub struct CustomEventContent {
+    /// A custom msgtype
+    pub msgtype: String,
+
+    /// Remaining event content
+    #[serde(flatten)]
+    pub data: BTreeMap<String, JsonValue>,
+}

ruma-events/src/room/message/content_serde.rs

@@ -32,7 +32,7 @@ impl<'de> de::Deserialize<'de> for MessageEventContent {
             "m.video" => Self::Video(from_raw_json_value(&json)?),
             #[cfg(feature = "unstable-pre-spec")]
             "m.key.verification.request" => Self::VerificationRequest(from_raw_json_value(&json)?),
-            _ => return Err(de::Error::custom("unknown msgtype")),
+            _ => Self::_Custom(from_raw_json_value(&json)?),
         })
     }
 }

ruma-events/tests/room_message.rs

@@ -1,6 +1,7 @@
 use std::time::{Duration, UNIX_EPOCH};
 
 use assign::assign;
+use maplit::btreemap;
 use matches::assert_matches;
 #[cfg(feature = "unstable-pre-spec")]
 use ruma_events::{
@@ -9,7 +10,8 @@ use ruma_events::{
 use ruma_events::{
     room::{
         message::{
-            AudioMessageEventContent, MessageEventContent, Relation, TextMessageEventContent,
+            AudioMessageEventContent, CustomEventContent, MessageEventContent, Relation,
+            TextMessageEventContent,
         },
         relationships::InReplyTo,
     },
@@ -73,6 +75,53 @@ fn content_serialization() {
     );
 }
 
+#[test]
+fn custom_content_serialization() {
+    let json_data = btreemap! {
+        "custom_field".into() => json!("baba"),
+        "another_one".into() => json!("abab"),
+    };
+    let custom_event_content = MessageEventContent::_Custom(CustomEventContent {
+        msgtype: "my_custom_msgtype".into(),
+        data: json_data,
+    });
+
+    assert_eq!(
+        to_json_value(&custom_event_content).unwrap(),
+        json!({
+            "msgtype": "my_custom_msgtype",
+            "custom_field": "baba",
+            "another_one": "abab",
+        })
+    );
+}
+
+#[test]
+fn custom_content_deserialization() {
+    let json_data = json!({
+        "msgtype": "my_custom_msgtype",
+        "custom_field": "baba",
+        "another_one": "abab",
+    });
+
+    let expected_json_data = btreemap! {
+        "custom_field".into() => json!("baba"),
+        "another_one".into() => json!("abab"),
+    };
+
+    assert_matches!(
+        from_json_value::<Raw<MessageEventContent>>(json_data)
+            .unwrap()
+            .deserialize()
+            .unwrap(),
+        MessageEventContent::_Custom(CustomEventContent {
+            msgtype,
+            data
+        }) if msgtype == "my_custom_msgtype"
+            && data == expected_json_data
+    );
+}
+
 #[test]
 fn formatted_body_serialization() {
     let message_event_content = MessageEventContent::Text(TextMessageEventContent::html(