Fix JS Generator Identifier when name is camel case

src/google/protobuf/compiler/js/js_generator.cc

@@ -294,6 +294,64 @@ std::vector<std::string> ParseUpperCamel(const std::string& input) {
   return words;
 }
 
+std::vector<std::string> ParseLowerCamel(const std::string& input) {
+  std::vector<std::string> words;
+  std::string running = "";
+  for (int i = 0; i < input.size(); i++) {
+    if (i != 0 && input[i] >= 'A' && input[i] <= 'Z' && !running.empty()) {
+      words.push_back(running);
+      running.clear();
+    }
+    running += ToLowerASCII(input[i]);
+  }
+  if (!running.empty()) {
+    words.push_back(running);
+  }
+  return words;
+}
+
+bool HasUpper(const std::string& input) {
+    for (int i = 0; i < input.size(); i++) {
+        if (input[i] >= 'A' && input[i] <= 'Z') {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+bool IsUpperCamel(const std::string& input) {
+    if (input.empty()) {
+        return false;
+    }
+
+    if (input.find('_') != std::string::npos) {
+        return false;
+    }
+
+    if (input[0] < 'A' || input[0] > 'Z') {
+        return false;
+    }
+
+    return HasUpper(input);
+}
+
+bool IsLowerCamel(const std::string& input) {
+    if (input.empty()) {
+        return false;
+    }
+
+    if (input.find('_') != std::string::npos) {
+        return false;
+    }
+
+    if (input[0] >= 'A' && input[0] <= 'Z') {
+        return false;
+    }
+
+    return HasUpper(input);
+}
+
 std::string ToLowerCamel(const std::vector<std::string>& words) {
   std::string result;
   for (int i = 0; i < words.size(); i++) {
@@ -462,14 +520,27 @@ std::string JSIdent(const GeneratorOptions& options,
                     const FieldDescriptor* field, bool is_upper_camel,
                     bool is_map, bool drop_list) {
   std::string result;
+
   if (field->type() == FieldDescriptor::TYPE_GROUP) {
-    result = is_upper_camel
-                 ? ToUpperCamel(ParseUpperCamel(field->message_type()->name()))
-                 : ToLowerCamel(ParseUpperCamel(field->message_type()->name()));
+      result = is_upper_camel
+               ? ToUpperCamel(ParseUpperCamel(field->message_type()->name()))
+               : ToLowerCamel(ParseUpperCamel(field->message_type()->name()));
   } else {
-    result = is_upper_camel ? ToUpperCamel(ParseLowerUnderscore(field->name()))
-                            : ToLowerCamel(ParseLowerUnderscore(field->name()));
+      if (is_upper_camel && IsUpperCamel(field->name())) {
+          result = field->name();
+      } else if (is_upper_camel && IsLowerCamel(field->name())) {
+          result = ToUpperCamel(ParseLowerCamel(field->name()));
+      } else if (!is_upper_camel && IsLowerCamel(field->name())) {
+          result = field->name();
+      } else if (!is_upper_camel && IsUpperCamel(field->name())) {
+          result = ToLowerCamel(ParseUpperCamel(field->name()));
+      } else if (is_upper_camel) {
+          result = ToUpperCamel(ParseLowerUnderscore(field->name()));
+      } else {
+          result = ToLowerCamel(ParseLowerUnderscore(field->name()));
+      }
   }
+
   if (is_map || field->is_map()) {
     // JSPB-style or proto3-style map.
     result += "Map";