change UNEXPECTED_ERROR data to string

Author: sistemd

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - `starknet_getEvents` incorrectly evaluates empty sub-lists in key filters for pending events.
+- For `UNEXPECTED_ERROR`, change the `data` field into a `string` to comply with the spec.
 
 ## [0.10.3] - 2024-01-04
 

crates/rpc/src/error.rs

@@ -199,9 +199,7 @@ impl ApplicationError {
                 "limit": limit,
                 "requested": requested,
             })),
-            ApplicationError::UnexpectedError { data } => Some(json!({
-                "error": data,
-            })),
+            ApplicationError::UnexpectedError { data } => Some(json!(data)),
             ApplicationError::ProofLimitExceeded { limit, requested } => Some(json!({
                 "limit": limit,
                 "requested": requested,