perf: drop a ~67 KiB duplicate prost decode tree + hoist a per-message traversal

src/message/dispatch.rs

@@ -15,10 +15,9 @@ impl Client {
 
         let mut info = Arc::clone(info);
         if info.ephemeral_expiration.is_none()
-            && msg.get_base_message().get_ephemeral_expiration().is_some()
+            && let Some(exp) = msg.get_base_message().get_ephemeral_expiration()
         {
-            Arc::make_mut(&mut info).ephemeral_expiration =
-                msg.get_base_message().get_ephemeral_expiration();
+            Arc::make_mut(&mut info).ephemeral_expiration = Some(exp);
         }
 
         // Keep this ordered with dispatch; add-on messages can immediately

wacore/src/messages.rs

@@ -1,7 +1,8 @@
 use crate::libsignal::crypto::CryptographicHash;
 use anyhow::{Result, anyhow};
 use base64::Engine as _;
-use prost::Message as ProtoMessage;
+#[cfg(test)]
+use prost::Message as _;
 use waproto::whatsapp as wa;
 
 pub struct MessageUtils;
@@ -98,8 +99,11 @@ impl MessageUtils {
                 let ctx = owned
                     .message_context_info
                     .get_or_insert_with(Default::default);
-                ctx.merge(waproto::codec::message_context_info_to_vec(extra).as_slice())
-                    .expect("merge MessageContextInfo");
+                waproto::codec::message_context_info_merge(
+                    ctx,
+                    &waproto::codec::message_context_info_to_vec(extra),
+                )
+                .expect("merge MessageContextInfo");
             }
             return Self::encode_dm_plaintexts_owned(owned, destination_jid);
         }

waproto/src/lib.rs

@@ -84,4 +84,20 @@ pub mod codec {
     pub fn message_context_info_to_vec(mci: &whatsapp::MessageContextInfo) -> Vec<u8> {
         mci.encode_to_vec()
     }
+
+    /// Merge wire bytes into an existing `MessageContextInfo` (prost merge
+    /// semantics: later-set fields win).
+    ///
+    /// Merges through a `&mut &mut &[u8]` buffer — the exact shape
+    /// `Message::decode` threads into its nested `MessageContextInfo` — so the
+    /// `BotMetadata` decode subtree reuses that instantiation instead of
+    /// emitting a second ~67 KiB copy in a distinct buffer-type shape.
+    #[inline(never)]
+    pub fn message_context_info_merge(
+        mci: &mut whatsapp::MessageContextInfo,
+        bytes: &[u8],
+    ) -> Result<(), prost::DecodeError> {
+        let mut cursor = bytes;
+        mci.merge(&mut &mut cursor)
+    }
 }