From 6f3adbb2d0f2269eb3ad81a8af557e90e59774a3 Mon Sep 17 00:00:00 2001
From: benluelo <benluelo@hotmail.com>
Date: Tue, 17 Oct 2023 12:07:32 +0100
Subject: [PATCH] fix(serde-utils): decode empty hex properly

---
 lib/serde-utils/Cargo.toml |  6 +++++-
 lib/serde-utils/src/lib.rs | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/serde-utils/Cargo.toml b/lib/serde-utils/Cargo.toml
index 1e3ce1f848..535b1c9e1e 100644
--- a/lib/serde-utils/Cargo.toml
+++ b/lib/serde-utils/Cargo.toml
@@ -7,6 +7,10 @@ edition = "2021"
 [dependencies]
 base64 = { version = "0.21", default-features = false, features = ["alloc"] }
 serde = { version = "1.0", default-features = false }
-hex = { version = "0.4.3", default-features = false }
+hex = { version = "0.4.3", default-features = false, features = ["alloc"] }
 primitive-types = { version = "0.12.1", default-features = false, features = ["serde_no_std"] }
 bitvec = "1.0.1"
+
+[dev-dependencies]
+hex = { version = "0.4.3" }
+
diff --git a/lib/serde-utils/src/lib.rs b/lib/serde-utils/src/lib.rs
index 9a6f51c140..912ebf092d 100644
--- a/lib/serde-utils/src/lib.rs
+++ b/lib/serde-utils/src/lib.rs
@@ -1,6 +1,6 @@
 extern crate alloc;
 
-use std::fmt::Debug;
+use core::fmt::Debug;
 
 use hex::FromHexError;
 
@@ -66,6 +66,9 @@ where
     }
 
     match s.strip_prefix(HEX_ENCODING_PREFIX.as_bytes()) {
+        Some([b'0']) => {
+            T::try_from(vec![]).map_err(|err| FromHexStringError::TryFromBytes(format!("{err:?}")))
+        }
         Some(maybe_hex) => hex::decode(maybe_hex)
             .map_err(FromHexStringError::Hex)?
             .try_into()
@@ -335,3 +338,13 @@ pub mod bitvec_string {
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn hex() {
+        parse_hex::<Vec<u8>>(to_hex([])).unwrap();
+    }
+}