contract-dev/techniques/contract-sharding.mdx (1)

90-102: ⚠️ Potential issue | 🟠 Major | ⚡ Quick win

child.tolk: empty top-up fallback likely won’t run after upfront parse.

On Line 91, lazy TodoChildMessage.fromSlice(in.body) runs before the Line 100 empty-body fallback. If fromSlice rejects empty/unknown bodies first, the intended “ignore empty top-up” path is unreachable.

Suggested doc snippet fix

 fun onInternalMessage(in: InMessage) {
+    if (in.body.isEmpty()) {
+        return;
+    }
     val msg = lazy TodoChildMessage.fromSlice(in.body);

     match (msg) {
         Identify => {
             val storage = lazy TodoChildStorage.load();
             assert (in.senderAddress == storage.parentAddress) throw 0xFFFF;
             debug.print(storage.seqno);
         }
-        else => {
-            // Ignore empty top-up messages, reject everything else.
-            assert (in.body.isEmpty()) throw 0xFFFF;
-        }
+        else => { throw 0xFFFF; }
     }
 }

In Tolk, does `lazy <UnionType>.fromSlice(in.body)` throw on an empty body or unknown opcode before `match` fallback branches can execute?

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@contract-dev/techniques/contract-sharding.mdx` around lines 90 - 102, The
current code eagerly calls TodoChildMessage.fromSlice(in.body) in
onInternalMessage which can throw on empty/unknown payloads and prevents the
intended empty-body fallback; fix by deferring parsing: first check
in.body.isEmpty() (or use a non-throwing/optional parse helper) and handle the
empty top-up branch before calling TodoChildMessage.fromSlice, or move the
fromSlice call inside the Identify match arm so parsing only happens when the
message is non-empty and intended to be parsed.

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes