From 4da1e29320a75cd22accf835b26a696bae2bad68 Mon Sep 17 00:00:00 2001
From: Conor Patrick <conorpp94@gmail.com>
Date: Mon, 13 Apr 2026 09:30:36 -0400
Subject: [PATCH] signer/core/apitypes: fix encoding of opening parenthesis
 (#33702)

This fixes a truncation bug that results in an invalid serialization of
empty EIP712.

For example:

```json
{
    "method": "eth_signTypedData_v4",
    "request": {
        "types": {
            "EIP712Domain": [
                {
                    "name": "version",
                    "type": "string"
                }
            ],
            "Empty": []
        },
        "primaryType": "Empty",
        "domain": {
            "version": "0"
        },
        "message": {}
    }
}
```

When calculating the type-hash for the stuct-hash, it will incorrectly
use `Empty)` instead of `Empty()`
---
 signer/core/apitypes/types.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/signer/core/apitypes/types.go b/signer/core/apitypes/types.go
index 401f4fba07..ee12bb263e 100644
--- a/signer/core/apitypes/types.go
+++ b/signer/core/apitypes/types.go
@@ -454,7 +454,9 @@ func (typedData *TypedData) EncodeType(primaryType string) hexutil.Bytes {
 			buffer.WriteString(obj.Name)
 			buffer.WriteString(",")
 		}
-		buffer.Truncate(buffer.Len() - 1)
+		if len(typedData.Types[dep]) > 0 {
+			buffer.Truncate(buffer.Len() - 1)
+		}
 		buffer.WriteString(")")
 	}
 	return buffer.Bytes()