Fixed missing comma problem in JSON output from PEG playground parser

docs/native.cpp

@@ -18,10 +18,9 @@ std::string escape_json(const std::string& s) {
   return o.str();
 }
 
-std::function<void(size_t, size_t, const std::string&)> makeJSONFormatter(std::string& json) {
-  auto init = std::make_shared<bool>(true);
-
-  return [&json, init](size_t ln, size_t col, const std::string& msg) mutable {
+std::function<void(size_t, size_t, const std::string&)> makeJSONFormatter(std::string& json, bool& init) {
+  init = true;
+  return [&](size_t ln, size_t col, const std::string& msg) mutable {
     if (!init) {
       json += ",";
     }
@@ -30,12 +29,14 @@ std::function<void(size_t, size_t, const std::string&)> makeJSONFormatter(std::s
     json += R"("col":)" + std::to_string(col) + ",";
     json += R"("msg":")" + escape_json(msg) + R"(")";
     json += "}";
-    *init = false;
+
+    init = false;
   };
 }
 
 bool parse_grammar(const std::string& text, peg::parser& peg, std::string& json) {
-  peg.log = makeJSONFormatter(json);
+  bool init;
+  peg.log = makeJSONFormatter(json, init);
   json += "[";
   auto ret = peg.load_grammar(text.data(), text.size());
   json += "]";
@@ -45,7 +46,8 @@ bool parse_grammar(const std::string& text, peg::parser& peg, std::string& json)
 bool parse_code(const std::string& text, peg::parser& peg, std::string& json,
                 std::shared_ptr<peg::Ast>& ast) {
   peg.enable_ast();
-  peg.log = makeJSONFormatter(json);
+  bool init;
+  peg.log = makeJSONFormatter(json, init);
   json += "[";
   auto ret = peg.parse_n(text.data(), text.size(), ast);
   json += "]";