Preserve JSON input object order

Function-runner parses JSON inputs into serde_json::Value and reserializes them before passing bytes to the WASM. With serde_json's default map implementation, this sorts object keys lexicographically, which can change JS behavior that depends on Object.keys() ordering for fallback logic.\n\nEnable serde_json's preserve_order feature so JSON input object key order is retained, and add a regression test covering nested metafield-like message objects. This keeps function-rerunner parity closer to production inputs for Checkout Blocks discount functions.\n\nVerified with:\n- cargo test json_input_preserves_object_key_order_in_raw_bytes\n- cargo build --release\n- cargo test\n- Rerunning the 17 discount localized-message mismatch rows with the fixed release runner produced full semantic matches.

Assisted-By: devx/c659e918-9568-4750-b122-e3890447348a

Author: dnagoda

Cargo.lock

@@ -50,7 +50,7 @@ wasmtime-wasi = "=39.0.1"
 deterministic-wasi-ctx = "=3.0.4"
 anyhow = "1.0"
 clap = { version = "4.5", features = ["derive"] }
-serde_json = "1.0"
+serde_json = { version = "1.0", features = ["preserve_order"] }
 colored = "3.1"
 serde = "1.0"
 rust-embed = "8.11.0"

Cargo.toml

@@ -136,3 +136,21 @@ impl BytesContainer {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn json_input_preserves_object_key_order_in_raw_bytes() {
+        let raw = br#"{"msg":{"sq-XK":"5.00 EUR Zbritje","en":"5.00 EUR Discount"}}"#.to_vec();
+
+        let input = BytesContainer::new(BytesContainerType::Input, Codec::Json, raw.clone())
+            .expect("valid JSON input");
+
+        assert_eq!(
+            String::from_utf8(input.raw).unwrap(),
+            String::from_utf8(raw).unwrap()
+        );
+    }
+}