Crate ruma_events[−][src]

Expand description

(De)serializable types for the events in the Matrix specification. These types are used by other ruma crates.

All data exchanged over Matrix is expressed as an event. Different event types represent different actions, such as joining a room or sending a message. Events are stored and transmitted as simple JSON structures. While anyone can create a new event type for their own purposes, the Matrix specification defines a number of event types which are considered core to the protocol, and Matrix clients and servers must understand their semantics. ruma-events contains Rust types for each of the event types defined by the specification and facilities for extending the event system for custom event types.

Event types

ruma-events includes a Rust enum called EventType, which provides a simple enumeration of all the event types defined by the Matrix specification. Matrix event types are serialized to JSON strings in reverse domain name notation, although the core event types all use the special “m” TLD, e.g. m.room.message.

Core event types

ruma-events includes Rust types for every one of the event types in the Matrix specification. To better organize the crate, these types live in separate modules with a hierarchy that matches the reverse domain name notation of the event type. For example, the m.room.message event lives at ruma_events::room::message::MessageEvent. Each type’s module also contains a Rust type for that event type’s content field, and any other supporting types required by the event’s other fields.

Extending Ruma with custom events

For our example we will create a reaction message event. This can be used with ruma-events structs, for this event we will use a SyncMessageEvent struct but any MessageEvent struct would work.

use ruma_events::{macros::EventContent, SyncMessageEvent};
use ruma_identifiers::EventId;
use serde::{Deserialize, Serialize};

#[derive(Clone, Debug, Deserialize, Serialize)]
#[serde(tag = "rel_type")]
pub enum RelatesTo {
    #[serde(rename = "m.annotation")]
    Annotation {
        /// The event this reaction relates to.
        event_id: EventId,
        /// The displayable content of the reaction.
        key: String,
    },

    /// Since this event is not fully specified in the Matrix spec
    /// it may change or types may be added, we are ready!
    #[serde(rename = "m.whatever")]
    Whatever,
}

/// The payload for our reaction event.
#[derive(Clone, Debug, Deserialize, Serialize, EventContent)]
#[ruma_event(type = "m.reaction", kind = Message)]
pub struct ReactionEventContent {
    #[serde(rename = "m.relates_to")]
    pub relates_to: RelatesTo,
}

let json = serde_json::json!({
    "content": {
        "m.relates_to": {
            "event_id": "$xxxx-xxxx",
            "key": "👍",
            "rel_type": "m.annotation"
        }
    },
    "event_id": "$xxxx-xxxx",
    "origin_server_ts": 1,
    "sender": "@someone:example.org",
    "type": "m.reaction",
    "unsigned": {
        "age": 85
    }
});

// The downside of this event is we cannot use it with event enums,
// but could be deserialized from a `Raw<_>` that has failed to deserialize.
matches::assert_matches!(
    serde_json::from_value::<SyncMessageEvent<ReactionEventContent>>(json),
    Ok(SyncMessageEvent {
        content: ReactionEventContent {
            relates_to: RelatesTo::Annotation { key, .. },
        },
        ..
    }) if key == "👍"
);

Serialization and deserialization

All concrete event types in ruma-events can be serialized via the Serialize trait from serde and can be deserialized from as Raw<EventType>. In order to handle incoming data that may not conform to ruma-events’ strict definitions of event structures, deserialization will return Raw::Err on error. This error covers both structurally invalid JSON data as well as structurally valid JSON that doesn’t fulfill additional constraints the matrix specification defines for some event types. The error exposes the deserialized serde_json::Value so that developers can still work with the received event data. This makes it possible to deserialize a collection of events without the entire collection failing to deserialize due to a single invalid event. The “content” type for each event also implements Serialize and either TryFromRaw (enabling usage as Raw<ContentType> for dedicated content types) or Deserialize (when the content is a type alias), allowing content to be converted to and from JSON independently of the surrounding event structure, if needed.