feat: improve type assertion messages with actual ValueType (#1627)

When indexing into a Json::Value, several assertions check that the value is an object or array. This commit enhances the error messages by reporting the actual type found, making it easier for users to debug type mismatch issues.

Fixes #1627

Author: baylesj

src/lib_json/json_value.cpp

@@ -193,6 +193,24 @@ static inline void releaseStringValue(char* value, unsigned) { free(value); }
 // ValueInternals...
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////
+
+namespace Json {
+
+static const char* valueTypeToString(ValueType type) {
+  switch (type) {
+  case nullValue: return "nullValue";
+  case intValue: return "intValue";
+  case uintValue: return "uintValue";
+  case realValue: return "realValue";
+  case stringValue: return "stringValue";
+  case booleanValue: return "booleanValue";
+  case arrayValue: return "arrayValue";
+  case objectValue: return "objectValue";
+  }
+  return "unknown";
+}
+
+} // namespace Json
 // //////////////////////////////////////////////////////////////////
 #if !defined(JSON_IS_AMALGAMATION)
 
@@ -929,7 +947,7 @@ void Value::clear() {
 
 void Value::resize(ArrayIndex newSize) {
   JSON_ASSERT_MESSAGE(type() == nullValue || type() == arrayValue,
-                      "in Json::Value::resize(): requires arrayValue");
+                      "in Json::Value::resize(): requires arrayValue, but found " << valueTypeToString(type()));
   if (type() == nullValue)
     *this = Value(arrayValue);
   ArrayIndex oldSize = size();
@@ -1062,7 +1080,7 @@ void Value::dupMeta(const Value& other) {
 Value& Value::resolveReference(const char* key) {
   JSON_ASSERT_MESSAGE(
       type() == nullValue || type() == objectValue,
-      "in Json::Value::resolveReference(): requires objectValue");
+      "in Json::Value::resolveReference(): requires objectValue, but found " << valueTypeToString(type()));
   if (type() == nullValue)
     *this = Value(objectValue);
   CZString actualKey(key, static_cast<unsigned>(strlen(key)),
@@ -1081,7 +1099,7 @@ Value& Value::resolveReference(const char* key) {
 Value& Value::resolveReference(char const* key, char const* end) {
   JSON_ASSERT_MESSAGE(
       type() == nullValue || type() == objectValue,
-      "in Json::Value::resolveReference(key, end): requires objectValue");
+      "in Json::Value::resolveReference(key, end): requires objectValue, but found " << valueTypeToString(type()));
   if (type() == nullValue)
     *this = Value(objectValue);
   CZString actualKey(key, static_cast<unsigned>(end - key),
@@ -1192,7 +1210,7 @@ Value& Value::append(const Value& value) { return append(Value(value)); }
 
 Value& Value::append(Value&& value) {
   JSON_ASSERT_MESSAGE(type() == nullValue || type() == arrayValue,
-                      "in Json::Value::append: requires arrayValue");
+                      "in Json::Value::append: requires arrayValue, but found " << valueTypeToString(type()));
   if (type() == nullValue) {
     *this = Value(arrayValue);
   }
@@ -1252,7 +1270,7 @@ bool Value::removeMember(String const& key, Value* removed) {
 
 void Value::removeMember(const char* key) {
   JSON_ASSERT_MESSAGE(type() == nullValue || type() == objectValue,
-                      "in Json::Value::removeMember(): requires objectValue");
+                      "in Json::Value::removeMember(): requires objectValue, but found " << valueTypeToString(type()));
   if (type() == nullValue)
     return;
 
@@ -1707,3 +1725,4 @@ Value& Path::make(Value& root) const {
 const char* version() { return JSONCPP_VERSION_STRING; }
 
 } // namespace Json
+