Switch to uuid_v7 and tighten ConversationId usage (#3819)

Make sure conversations have a timestamp.

codex-rs/protocol/src/mcp_protocol.rs

@@ -19,13 +19,23 @@ use strum_macros::Display;
 use ts_rs::TS;
 use uuid::Uuid;
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, TS, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, TS, Hash)]
 #[ts(type = "string")]
-pub struct ConversationId(pub Uuid);
+pub struct ConversationId {
+    uuid: Uuid,
+}
 
 impl ConversationId {
     pub fn new() -> Self {
-        Self(Uuid::new_v4())
+        Self {
+            uuid: Uuid::now_v7(),
+        }
+    }
+
+    pub fn from_string(s: &str) -> Result<Self, uuid::Error> {
+        Ok(Self {
+            uuid: Uuid::parse_str(s)?,
+        })
     }
 }
 
@@ -37,19 +47,27 @@ impl Default for ConversationId {
 
 impl Display for ConversationId {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.0)
+        write!(f, "{}", self.uuid)
     }
 }
 
-impl From<Uuid> for ConversationId {
-    fn from(value: Uuid) -> Self {
-        Self(value)
+impl Serialize for ConversationId {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.collect_str(&self.uuid)
     }
 }
 
-impl From<ConversationId> for Uuid {
-    fn from(value: ConversationId) -> Self {
-        value.0
+impl<'de> Deserialize<'de> for ConversationId {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let value = String::deserialize(deserializer)?;
+        let uuid = Uuid::parse_str(&value).map_err(serde::de::Error::custom)?;
+        Ok(Self { uuid })
     }
 }
 
@@ -719,6 +737,27 @@ mod tests {
     #[test]
     fn test_conversation_id_default_is_not_zeroes() {
         let id = ConversationId::default();
-        assert_ne!(id.0, Uuid::nil());
+        assert_ne!(id.uuid, Uuid::nil());
+    }
+
+    #[test]
+    fn conversation_id_serializes_as_plain_string() {
+        let id = ConversationId::from_string("67e55044-10b1-426f-9247-bb680e5fe0c8").unwrap();
+
+        assert_eq!(
+            json!("67e55044-10b1-426f-9247-bb680e5fe0c8"),
+            serde_json::to_value(id).unwrap()
+        );
+    }
+
+    #[test]
+    fn conversation_id_deserializes_from_plain_string() {
+        let id: ConversationId =
+            serde_json::from_value(json!("67e55044-10b1-426f-9247-bb680e5fe0c8")).unwrap();
+
+        assert_eq!(
+            ConversationId::from_string("67e55044-10b1-426f-9247-bb680e5fe0c8").unwrap(),
+            id,
+        );
     }
 }

codex-rs/protocol/src/protocol.rs

@@ -1252,7 +1252,8 @@ mod tests {
     /// amount of nesting.
     #[test]
     fn serialize_event() {
-        let conversation_id = ConversationId(uuid::uuid!("67e55044-10b1-426f-9247-bb680e5fe0c8"));
+        let conversation_id =
+            ConversationId::from_string("67e55044-10b1-426f-9247-bb680e5fe0c8").unwrap();
         let rollout_file = NamedTempFile::new().unwrap();
         let event = Event {
             id: "1234".to_string(),