biomeos: centralized extract_rpc_error() — wetSpring V123 / healthSpring V30 pattern

Extracted structured (code, message) RPC error parsing into a single
extract_rpc_error() function. Handles standard JSON-RPC error objects
and bare string errors. parse_rpc_response() and response_has_error()
now delegate to it, eliminating duplicated extraction logic.

+4 tests (standard, bare string, absent error, method-not-found code).
916+ tests total.

Made-with: Cursor

Author: BiomeOS Developer

crates/groundspring/src/biomeos/protocol.rs

@@ -18,17 +18,32 @@ pub(super) fn build_request(method: &str, params: &Value) -> String {
     .to_string()
 }
 
+/// Extract structured error from a JSON-RPC 2.0 response.
+///
+/// Returns `Some((code, message))` if the response contains an `error` field,
+/// `None` if no error is present. Handles both standard JSON-RPC error objects
+/// (`{"code": -32600, "message": "..."}`) and bare string errors.
+///
+/// Pattern source: wetSpring V123 / healthSpring V30 centralized RPC error extraction.
+pub(super) fn extract_rpc_error(v: &Value) -> Option<(i64, String)> {
+    let error = v.get("error")?;
+    let code = error.get("code").and_then(Value::as_i64).unwrap_or(-32000);
+    let message = error
+        .get("message")
+        .and_then(Value::as_str)
+        .map(String::from)
+        .or_else(|| error.as_str().map(String::from))
+        .unwrap_or_else(|| "unknown RPC error".to_string());
+    Some((code, message))
+}
+
 /// Parse a JSON-RPC 2.0 response, extracting the result or error.
 pub(super) fn parse_rpc_response(response: &str) -> Result<String> {
     let v: Value = serde_json::from_str(response)
         .map_err(|e| BiomeOsError::Protocol(format!("invalid JSON-RPC response: {e}")))?;
 
-    if let Some(error) = v.get("error") {
-        let msg = error
-            .get("message")
-            .and_then(Value::as_str)
-            .unwrap_or("unknown RPC error");
-        return Err(BiomeOsError::Protocol(msg.to_string()));
+    if let Some((_code, message)) = extract_rpc_error(&v) {
+        return Err(BiomeOsError::Protocol(message));
     }
 
     match v.get("result") {
@@ -45,12 +60,8 @@ pub(super) fn response_has_error(response: &str) -> Result<()> {
     let v: Value = serde_json::from_str(response)
         .map_err(|e| BiomeOsError::Protocol(format!("invalid JSON-RPC response: {e}")))?;
 
-    if let Some(error) = v.get("error") {
-        let msg = error
-            .get("message")
-            .and_then(Value::as_str)
-            .unwrap_or("unknown RPC error");
-        return Err(BiomeOsError::Protocol(msg.to_string()));
+    if let Some((_code, message)) = extract_rpc_error(&v) {
+        return Err(BiomeOsError::Protocol(message));
     }
 
     Ok(())
@@ -120,4 +131,37 @@ mod tests {
         let resp = r#"{"jsonrpc":"2.0","error":{"code":-32600,"message":"bad"},"id":1}"#;
         assert!(response_has_error(resp).is_err());
     }
+
+    #[test]
+    fn extract_rpc_error_standard() {
+        let v: Value =
+            serde_json::from_str(r#"{"error":{"code":-32601,"message":"method not found"}}"#)
+                .unwrap();
+        let (code, msg) = extract_rpc_error(&v).unwrap();
+        assert_eq!(code, -32601);
+        assert_eq!(msg, "method not found");
+    }
+
+    #[test]
+    fn extract_rpc_error_bare_string() {
+        let v: Value = serde_json::from_str(r#"{"error":"something went wrong"}"#).unwrap();
+        let (code, msg) = extract_rpc_error(&v).unwrap();
+        assert_eq!(code, -32000);
+        assert_eq!(msg, "something went wrong");
+    }
+
+    #[test]
+    fn extract_rpc_error_none_when_no_error() {
+        let v: Value = serde_json::from_str(r#"{"result":"ok"}"#).unwrap();
+        assert!(extract_rpc_error(&v).is_none());
+    }
+
+    #[test]
+    fn extract_rpc_error_is_method_not_found() {
+        let v: Value =
+            serde_json::from_str(r#"{"error":{"code":-32601,"message":"method not found"}}"#)
+                .unwrap();
+        let (code, _) = extract_rpc_error(&v).unwrap();
+        assert_eq!(code, -32601);
+    }
 }