fix(rpc): allow query latest block (#1760)

## Overview

Allow querying latest `/block` without requiring `?height=` param for
CometBFT compat.

Fixes #1758 

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Enhanced parameter handling to support `*StrInt64` type with improved
error handling.

- **Bug Fixes**
- Fixed handling of nullable `Height` parameter in `Block` function to
prevent potential dereference issues.

- **Tests**
- Updated test cases to cover scenarios for valid/malformed requests and
different parameter conditions.

- **Refactor**
- Modified `Height` field in `blockArgs` struct to use `*StrInt64` for
better nullability support.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: tuxcanfly

rpc/json/handler.go

@@ -131,13 +131,17 @@ func (h *handler) newHandler(methodSpec *method) func(http.ResponseWriter, *http
 		for i := 0; i < methodSpec.argsType.NumField(); i++ {
 			field := methodSpec.argsType.Field(i)
 			name := field.Tag.Get("json")
-			if !values.Has(name) {
+			kind := field.Type.Kind()
+			// pointers can be skipped from required check
+			if kind != reflect.Pointer && !values.Has(name) {
 				h.encodeAndWriteResponse(w, nil, fmt.Errorf("missing param '%s'", name), int(json2.E_INVALID_REQ))
 				return
 			}
 			rawVal := values.Get(name)
 			var err error
-			switch field.Type.Kind() {
+			switch kind {
+			case reflect.Pointer:
+				err = setPointerParam(rawVal, &args, i)
 			case reflect.Bool:
 				err = setBoolParam(rawVal, &args, i)
 			case reflect.Int, reflect.Int64:
@@ -204,6 +208,26 @@ func (h *handler) encodeAndWriteResponse(w http.ResponseWriter, result interface
 	}
 }
 
+func setPointerParam(rawVal string, args *reflect.Value, i int) error {
+	if rawVal == "" {
+		return nil
+	}
+	field := args.Elem().Field(i)
+	switch {
+	// only *StrInt64 is supported for now
+	case field.Type() == reflect.TypeOf(blockArgs{}.Height):
+		val, err := strconv.ParseInt(rawVal, 10, 64)
+		if err != nil {
+			return err
+		}
+		strInt64Val := StrInt64(val)
+		args.Elem().Field(i).Set(reflect.ValueOf(&strInt64Val))
+		return nil
+	default:
+		return fmt.Errorf("unsupported pointer type: %v", field)
+	}
+}
+
 func setBoolParam(rawVal string, args *reflect.Value, i int) error {
 	v, err := strconv.ParseBool(rawVal)
 	if err != nil {

rpc/json/service.go

@@ -179,7 +179,12 @@ func (s *service) GenesisChunked(req *http.Request, args *genesisChunkedArgs) (*
 }
 
 func (s *service) Block(req *http.Request, args *blockArgs) (*ctypes.ResultBlock, error) {
-	return s.client.Block(req.Context(), (*int64)(&args.Height))
+	var height *int64
+	if args.Height != nil {
+		h := int64(*args.Height)
+		height = &h
+	}
+	return s.client.Block(req.Context(), height)
 }
 
 func (s *service) BlockByHash(req *http.Request, args *blockByHashArgs) (*ctypes.ResultBlock, error) {

rpc/json/service_test.go

@@ -64,10 +64,11 @@ func TestREST(t *testing.T) {
 		bodyContains string
 	}{
 
-		{"invalid/malformed request", "/block?so{}wrong!", http.StatusOK, int(json2.E_INVALID_REQ), ``},
-		{"invalid/missing param", "/block", http.StatusOK, int(json2.E_INVALID_REQ), `missing param 'height'`},
-		{"valid/no params", "/abci_info", http.StatusOK, -1, `"last_block_height":"345"`},
+		{"valid/malformed request", "/block?so{}wrong!", http.StatusOK, int(json2.E_INTERNAL), ``},
 		// to keep test simple, allow returning application error in following case
+		{"invalid/missing required param", "/header", http.StatusOK, int(json2.E_INVALID_REQ), `missing param 'height'`},
+		{"valid/missing optional param", "/block", http.StatusOK, int(json2.E_INTERNAL), "failed to load hash from index"},
+		{"valid/no params", "/abci_info", http.StatusOK, -1, `"last_block_height":"345"`},
 		{"valid/int param", "/block?height=321", http.StatusOK, int(json2.E_INTERNAL), "failed to load hash from index"},
 		{"invalid/int param", "/block?height=foo", http.StatusOK, int(json2.E_PARSE), "failed to parse param 'height'"},
 		{"valid/bool int string params",

rpc/json/types.go

@@ -36,7 +36,7 @@ type genesisChunkedArgs struct {
 	ID StrInt `json:"chunk"`
 }
 type blockArgs struct {
-	Height StrInt64 `json:"height"`
+	Height *StrInt64 `json:"height"`
 }
 type blockByHashArgs struct {
 	Hash []byte `json:"hash"`