feat: add toStyledString overloads for custom builder and precision

Add Value::toStyledString(const StreamWriterBuilder&) and Value::toStyledString(unsigned int, PrecisionType) while keeping the existing no-argument overload for ABI compatibility. Skip the leading newline when the builder suppresses comments.

Fixes open-source-parsers#1616

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Jingfu Yan

include/json/value.h

@@ -677,6 +677,11 @@ class JSON_API Value {
   String getComment(CommentPlacement placement) const;
 
   String toStyledString() const;
+  /// Serialize using the settings of \p builder.
+  String toStyledString(const StreamWriterBuilder& builder) const;
+  /// Serialize with the given floating-point precision (capped at 17).
+  String toStyledString(unsigned int precision,
+                        PrecisionType precisionType) const;
 
   const_iterator begin() const;
   const_iterator end() const;

src/lib_json/json_value.cpp

@@ -1556,14 +1556,29 @@ ptrdiff_t Value::getOffsetLimit() const { return limit_; }
 
 String Value::toStyledString() const {
   StreamWriterBuilder builder;
+  return toStyledString(builder);
+}
 
-  String out = this->hasComment(commentBefore) ? "\n" : "";
+String Value::toStyledString(const StreamWriterBuilder& builder) const {
+  const bool emitComments =
+      builder.settings_["commentStyle"].asString() != "None";
+  String out = (emitComments && this->hasComment(commentBefore)) ? "\n" : "";
   out += Json::writeString(builder, *this);
   out += '\n';
 
   return out;
 }
 
+String Value::toStyledString(unsigned int precision,
+                             PrecisionType precisionType) const {
+  StreamWriterBuilder builder;
+  builder.settings_["precisionType"] =
+      precisionType == PrecisionType::significantDigits ? "significant"
+                                                        : "decimal";
+  builder.settings_["precision"] = precision;
+  return toStyledString(builder);
+}
+
 Value::const_iterator Value::begin() const {
   switch (type()) {
   case arrayValue:

src/test_lib_json/main.cpp

@@ -2093,6 +2093,32 @@ JSONTEST_FIXTURE_LOCAL(ValueTest, CommentBefore) {
   }
 }
 
+JSONTEST_FIXTURE_LOCAL(ValueTest, toStyledStringWithBuilder) {
+  Json::Value val(1);
+  val.setComment(Json::String("// comment"), Json::commentBefore);
+  Json::StreamWriterBuilder wbuilder;
+  JSONTEST_ASSERT_STRING_EQUAL("\n// comment\n1\n",
+                               val.toStyledString(wbuilder));
+  wbuilder.settings_["commentStyle"] = "None";
+  JSONTEST_ASSERT_STRING_EQUAL("1\n", val.toStyledString(wbuilder));
+
+  Json::Value obj;
+  obj["a"] = 1;
+  wbuilder.settings_["indentation"] = "";
+  JSONTEST_ASSERT_STRING_EQUAL("{\"a\":1}\n", obj.toStyledString(wbuilder));
+}
+
+JSONTEST_FIXTURE_LOCAL(ValueTest, toStyledStringWithPrecision) {
+  Json::Value val(3.14159265);
+  JSONTEST_ASSERT_STRING_EQUAL(
+      "3.14\n", val.toStyledString(2, Json::PrecisionType::decimalPlaces));
+  JSONTEST_ASSERT_STRING_EQUAL(
+      "3.1\n", val.toStyledString(2, Json::PrecisionType::significantDigits));
+  JSONTEST_ASSERT_STRING_EQUAL(
+      val.toStyledString(17, Json::PrecisionType::significantDigits),
+      val.toStyledString(100, Json::PrecisionType::significantDigits));
+}
+
 JSONTEST_FIXTURE_LOCAL(ValueTest, zeroes) {
   char const cstr[] = "h\0i";
   Json::String binary(cstr, sizeof(cstr)); // include trailing 0