fix: JSON-RPC error:null + omit empty params (BTC-family / Stellar)

common/json_rpc.go

@@ -371,7 +371,10 @@ func (r *JsonRpcResponse) ParseFromStream(ctx []context.Context, reader io.Reade
 		}
 	}
 
-	if len(temp.Error) > 0 {
+	// Bitcoin-family nodes often emit `"error": null` on success. Treat that
+	// (and missing error) as no error — ParseError("null") used to invent a
+	// server-side exception and fail the whole upstream attempt.
+	if len(temp.Error) > 0 && string(temp.Error) != "null" {
 		if err := r.ParseError(string(temp.Error)); err != nil {
 			return err
 		}
@@ -399,11 +402,17 @@ func (r *JsonRpcResponse) ParseError(raw string) error {
 
 	r.errBytes = nil
 
+	// JSON-RPC allows "error": null (Bitcoin Core / dogecoind / litecoind).
+	// That means success — do not fabricate a server-side exception.
+	if raw == "null" {
+		return nil
+	}
+
 	// First attempt to unmarshal the error as a typical JSON-RPC error
 	var rpcErr ErrJsonRpcExceptionExternal
 	if err := SonicCfg.UnmarshalFromString(raw, &rpcErr); err != nil {
 		// Special case: check for non-standard error structures in the raw data
-		if raw == "" || raw == "null" {
+		if raw == "" {
 			r.Error = NewErrJsonRpcExceptionExternal(
 				int(JsonRpcErrorServerSideException),
 				"unexpected empty response from upstream endpoint",
@@ -1205,7 +1214,10 @@ type JsonRpcRequest struct {
 	JSONRPC string        `json:"jsonrpc,omitempty"`
 	ID      interface{}   `json:"id,omitempty"`
 	Method  string        `json:"method"`
-	Params  []interface{} `json:"params"`
+	// omitempty: Stellar (and some other non-EVM) reject "params":[] — they
+	// expect the field absent (or an object). Empty/nil params are omitted on
+	// the wire; EVM nodes accept both forms.
+	Params []interface{} `json:"params,omitempty"`
 
 	// idRaw stores the verbatim bytes of the id as received from the client.
 	// This is used to round-trip the id back without precision loss for ids

common/json_rpc_test.go

@@ -219,10 +219,23 @@ func TestJsonRpcRequest_MarshalParams(t *testing.T) {
 		})
 		assert.NoError(t, err)
 
-		expectedRawReq := `{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}`
+		// Empty params omitted — required for Stellar / some non-EVM nodes
+		// that reject "params":[] (expect absent field or object).
+		expectedRawReq := `{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber"}`
 		assert.Equal(t, expectedRawReq, string(rawReq))
 	})
 
+	t.Run("Nil", func(t *testing.T) {
+		rawReq, err := SonicCfg.Marshal(JsonRpcRequest{
+			JSONRPC: "2.0",
+			ID:      1,
+			Method:  "getLatestLedger",
+			Params:  nil,
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, `{"jsonrpc":"2.0","id":1,"method":"getLatestLedger"}`, string(rawReq))
+	})
+
 	t.Run("Value", func(t *testing.T) {
 		rawReq, err := SonicCfg.Marshal(JsonRpcRequest{
 			JSONRPC: "2.0",
@@ -237,6 +250,20 @@ func TestJsonRpcRequest_MarshalParams(t *testing.T) {
 	})
 }
 
+func TestJsonRpcResponse_ErrorNullIsSuccess(t *testing.T) {
+	// Bitcoin-family (dogecoind/litecoind) returns "error":null on success.
+	raw := `{"result":67851510,"error":null,"id":1}`
+	r := &JsonRpcResponse{}
+	err := r.ParseFromStream(nil, bytes.NewReader([]byte(raw)), len(raw))
+	require.NoError(t, err)
+	assert.Nil(t, r.Error)
+	assert.Equal(t, "67851510", string(r.result))
+
+	r2 := &JsonRpcResponse{}
+	require.NoError(t, r2.ParseError("null"))
+	assert.Nil(t, r2.Error)
+}
+
 func TestJsonRpcResponse_CanonicalHash_EmptyishNormalization(t *testing.T) {
 	// Test cases that should produce the same hash due to emptyish normalization
 	testGroups := []struct {