Fix redacted aliases event deserialization

ruma-events-macros/src/event.rs

@@ -151,11 +151,18 @@ fn expand_deserialize_event(
         if name == "content" {
             if is_generic && ident.to_string().contains("Redacted") {
                 quote! {
-                    let content = if !C::has_deserialize_fields() {
-                        C::empty(&event_type).map_err(A::Error::custom)?
-                    } else {
-                        let json = content.ok_or_else(|| ::serde::de::Error::missing_field("content"))?;
-                        C::from_parts(&event_type, json).map_err(A::Error::custom)?
+                    let content = match C::has_deserialize_fields() {
+                        ::ruma_events::HasDeserializeFields::False => {
+                            C::empty(&event_type).map_err(A::Error::custom)?
+                        },
+                        ::ruma_events::HasDeserializeFields::True => {
+                            let json = content.ok_or_else(|| ::serde::de::Error::missing_field("content"))?;
+                            C::from_parts(&event_type, json).map_err(A::Error::custom)?
+                        },
+                        ::ruma_events::HasDeserializeFields::Optional => {
+                            let json = content.unwrap_or(::serde_json::value::RawValue::from_string("{}".to_string()).unwrap());
+                            C::from_parts(&event_type, json).map_err(A::Error::custom)?
+                        },
                     };
                 }
             } else if is_generic {

ruma-events-macros/src/event_content.rs

@@ -135,7 +135,13 @@ pub fn expand_event_content(input: &DeriveInput, emit_redacted: bool) -> syn::Re
             )
         };
 
-        let has_fields = if kept_redacted_fields.is_empty() {
+        let has_deserialize_fields = if kept_redacted_fields.is_empty() {
+            quote! { ::ruma_events::HasDeserializeFields::False }
+        } else {
+            quote! { ::ruma_events::HasDeserializeFields::True }
+        };
+
+        let has_serialize_fields = if kept_redacted_fields.is_empty() {
             quote! { false }
         } else {
             quote! { true }
@@ -170,11 +176,11 @@ pub fn expand_event_content(input: &DeriveInput, emit_redacted: bool) -> syn::Re
                 }
 
                 fn has_serialize_fields(&self) -> bool {
-                    #has_fields
+                    #has_serialize_fields
                 }
 
-                fn has_deserialize_fields() -> bool {
-                    #has_fields
+                fn has_deserialize_fields() -> ::ruma_events::HasDeserializeFields {
+                    #has_deserialize_fields
                 }
             }
         }

ruma-events/src/custom.rs

@@ -4,9 +4,9 @@ use serde::Serialize;
 use serde_json::{value::RawValue as RawJsonValue, Value as JsonValue};
 
 use crate::{
-    BasicEventContent, EphemeralRoomEventContent, EventContent, MessageEventContent,
-    RedactedEventContent, RedactedMessageEventContent, RedactedStateEventContent, RoomEventContent,
-    StateEventContent,
+    BasicEventContent, EphemeralRoomEventContent, EventContent, HasDeserializeFields,
+    MessageEventContent, RedactedEventContent, RedactedMessageEventContent,
+    RedactedStateEventContent, RoomEventContent, StateEventContent,
 };
 
 /// A custom event's type and `content` JSON object.
@@ -83,8 +83,8 @@ impl RedactedEventContent for RedactedCustomEventContent {
         false
     }
 
-    fn has_deserialize_fields() -> bool {
-        false
+    fn has_deserialize_fields() -> HasDeserializeFields {
+        HasDeserializeFields::False
     }
 }
 

ruma-events/src/lib.rs

@@ -243,20 +243,27 @@ pub trait StateEventContent: RoomEventContent {}
 
 /// The base trait that all redacted event content types implement.
 ///
-/// Implementing this trait allows content types to be serialized as well as deserialized.
+/// This trait's associated functions and methods should not be used to build
+/// redacted events, prefer the `redact` method on `AnyStateEvent` and
+/// `AnyMessageEvent` and their "sync" and "stripped" counterparts. The
+/// `RedactedEventContent` trait is an implementation detail, ruma makes no
+/// API guarantees.
 pub trait RedactedEventContent: EventContent {
     /// Constructs the redacted event content.
     ///
     /// If called for anything but "empty" redacted content this will error.
+    #[doc(hidden)]
     fn empty(_event_type: &str) -> Result<Self, serde_json::Error> {
         Err(serde::de::Error::custom("this event is not redacted"))
     }
 
     /// Determines if the redacted event content needs to serialize fields.
+    #[doc(hidden)]
     fn has_serialize_fields(&self) -> bool;
 
     /// Determines if the redacted event content needs to deserialize fields.
-    fn has_deserialize_fields() -> bool;
+    #[doc(hidden)]
+    fn has_deserialize_fields() -> HasDeserializeFields;
 }
 
 /// Marker trait for the content of a redacted message event.
@@ -265,6 +272,21 @@ pub trait RedactedMessageEventContent: RedactedEventContent {}
 /// Marker trait for the content of a redacted state event.
 pub trait RedactedStateEventContent: RedactedEventContent {}
 
+/// `HasDeserializeFields` is used in the code generated by the `Event` derive
+/// to aid in deserializing redacted events.
+#[doc(hidden)]
+#[derive(Debug)]
+pub enum HasDeserializeFields {
+    /// Deserialize the event's content, failing if invalid.
+    True,
+    /// Return the redacted version of this event's content.
+    False,
+    /// `Optional` is used for `RedactedAliasesEventContent` since it has
+    /// an empty version and one with content left after redaction that
+    /// must be supported together.
+    Optional,
+}
+
 /// Helper struct to determine if the event has been redacted.
 #[doc(hidden)]
 #[derive(Debug, Deserialize)]

ruma-events/src/room/aliases.rs

@@ -5,7 +5,9 @@ use ruma_identifiers::RoomAliasId;
 use serde::{Deserialize, Serialize};
 use serde_json::value::RawValue as RawJsonValue;
 
-use crate::{EventContent, RedactedEventContent, RedactedStateEventContent, StateEvent};
+use crate::{
+    EventContent, HasDeserializeFields, RedactedEventContent, RedactedStateEventContent, StateEvent,
+};
 
 /// Informs the room about what room aliases it has been given.
 pub type AliasesEvent = StateEvent<AliasesEventContent>;
@@ -53,8 +55,8 @@ impl RedactedEventContent for RedactedAliasesEventContent {
         self.aliases.is_some()
     }
 
-    fn has_deserialize_fields() -> bool {
-        true
+    fn has_deserialize_fields() -> HasDeserializeFields {
+        HasDeserializeFields::Optional
     }
 }
 

ruma-events/tests/redacted.rs

@@ -19,10 +19,6 @@ use ruma_events::{
 use ruma_identifiers::{EventId, RoomId, UserId};
 use serde_json::{from_value as from_json_value, json, to_value as to_json_value};
 
-fn is_zst<T>(_: &T) -> bool {
-    std::mem::size_of::<T>() == 0
-}
-
 fn full_unsigned() -> UnsignedData {
     let mut unsigned = UnsignedData::default();
     // The presence of `redacted_because` triggers the event enum to return early
@@ -63,7 +59,7 @@ fn redacted_message_event_serialize() {
 }
 
 #[test]
-fn redacted_aliases_event_serialize() {
+fn redacted_aliases_event_serialize_no_content() {
     let redacted = RedactedSyncStateEvent {
         content: RedactedAliasesEventContent { aliases: None },
         event_id: EventId::try_from("$h29iv0s8:example.com").unwrap(),
@@ -85,6 +81,32 @@ fn redacted_aliases_event_serialize() {
     assert_eq!(actual, expected);
 }
 
+#[test]
+fn redacted_aliases_event_serialize_with_content() {
+    let redacted = RedactedSyncStateEvent {
+        content: RedactedAliasesEventContent { aliases: Some(vec![]) },
+        event_id: EventId::try_from("$h29iv0s8:example.com").unwrap(),
+        state_key: "".to_string(),
+        origin_server_ts: UNIX_EPOCH + Duration::from_millis(1),
+        sender: UserId::try_from("@carl:example.com").unwrap(),
+        unsigned: UnsignedData::default(),
+    };
+
+    let expected = json!({
+      "content": {
+          "aliases": []
+      },
+      "event_id": "$h29iv0s8:example.com",
+      "state_key": "",
+      "origin_server_ts": 1,
+      "sender": "@carl:example.com",
+      "type": "m.room.aliases"
+    });
+
+    let actual = to_json_value(&redacted).unwrap();
+    assert_eq!(actual, expected);
+}
+
 #[test]
 fn redacted_aliases_deserialize() {
     let unsigned = full_unsigned();
@@ -101,14 +123,15 @@ fn redacted_aliases_deserialize() {
     let actual = to_json_value(&redacted).unwrap();
 
     assert_matches!(
-        from_json_value::<EventJson<AnyRoomEventStub>>(actual)
+        from_json_value::<EventJson<AnySyncRoomEvent>>(actual)
             .unwrap()
             .deserialize()
             .unwrap(),
-        AnyRoomEventStub::RedactedState(AnyRedactedStateEventStub::RoomAliases(RedactedStateEventStub {
-            event_id, content, ..
+        AnySyncRoomEvent::RedactedState(AnyRedactedSyncStateEvent::RoomAliases(RedactedSyncStateEvent {
+            content: RedactedAliasesEventContent { aliases },
+            event_id, ..
         })) if event_id == EventId::try_from("$h29iv0s8:example.com").unwrap()
-            && is_zst(&content)
+            && aliases.is_none()
     )
 }
 
@@ -133,10 +156,10 @@ fn redacted_deserialize_any_room() {
             .deserialize()
             .unwrap(),
         AnyRoomEvent::RedactedMessage(AnyRedactedMessageEvent::RoomMessage(RedactedMessageEvent {
-            event_id, room_id, content, ..
+            content: RedactedMessageEventContent,
+            event_id, room_id, ..
         })) if event_id == EventId::try_from("$h29iv0s8:example.com").unwrap()
             && room_id == RoomId::try_from("!roomid:room.com").unwrap()
-            && is_zst(&content)
     )
 }
 
@@ -172,9 +195,9 @@ fn redacted_deserialize_any_room_sync() {
             .deserialize()
             .unwrap(),
         AnySyncRoomEvent::RedactedMessage(AnyRedactedSyncMessageEvent::RoomMessage(RedactedSyncMessageEvent {
-            event_id, content, ..
+            content: RedactedMessageEventContent,
+            event_id, ..
         })) if event_id == EventId::try_from("$h29iv0s8:example.com").unwrap()
-            && is_zst(&content)
     )
 }