From a69502c3bd177a5ae502b7b9d13f260ffe19314e Mon Sep 17 00:00:00 2001
From: David Banks <47112877+dbanks12@users.noreply.github.com>
Date: Wed, 11 Dec 2024 14:28:44 -0500
Subject: [PATCH] fix: attempt to fix flake in e2e cross chain messaging test
 (#10634)

I was missing a case in this nullifier check assertion. There are
actually 2 ways for a low nullifier leaf to "skip" a target nullifier.
Low leaf nullifier < target nullifier and either:
1. low leaf next nullifier > target nullifier
2. or (was missing) low leaf's "next index" is 0 (it is the
largest-value nullifier in the tree)

I also switched the order of the left/right hand operands in the
assertion to match the very similar public data assertion.

The test failure I'm trying to fix is pasted below. I was unable to
replicate it locally.

![image](https://github.com/user-attachments/assets/262e435c-46c6-4b8f-9ad8-958a064fdd92)
---
 yarn-project/simulator/src/avm/journal/journal.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/yarn-project/simulator/src/avm/journal/journal.ts b/yarn-project/simulator/src/avm/journal/journal.ts
index 8cdc8dba107..2d0ab2f7a5f 100644
--- a/yarn-project/simulator/src/avm/journal/journal.ts
+++ b/yarn-project/simulator/src/avm/journal/journal.ts
@@ -379,8 +379,8 @@ export class AvmPersistableStateManager {
       } else {
         // Sanity check that the leaf value is skipped by low leaf when it doesn't exist
         assert(
-          siloedNullifier.toBigInt() > leafPreimage.nullifier.toBigInt() &&
-            siloedNullifier.toBigInt() < leafPreimage.nextNullifier.toBigInt(),
+          leafPreimage.nullifier.toBigInt() < siloedNullifier.toBigInt() &&
+            (leafPreimage.nextIndex === 0n || leafPreimage.nextNullifier.toBigInt() > siloedNullifier.toBigInt()),
           'Nullifier tree low leaf should skip the target leaf nullifier when the target leaf does not exist.',
         );
       }