Oracle pl/json to_clob() fails if json value is single character - json

Question

we are trying to use PL/JSON package for our programs but it looks like that json.to_clob method has a bug. If you try this code:
-- json to clob bug in pl/json package
-- if json value is single character then that json value will not be shown in clob
declare
l_Data_json_clob clob;
l_Data_json json;
begin
l_Data_json := json();
dbms_lob.createtemporary(l_Data_json_clob, true); -- create CLOB where result will be stored
l_Data_json.put('RESULT', '1');--put one character in json value
l_Data_json.to_clob(l_Data_json_clob);--put json result to clob
dbms_output.put_line(dbms_lob.substr( l_Data_json_clob, 255, 1));--not correct json - json value is empty
l_Data_json.put('RESULT', '22');--put two characters in json value
l_Data_json.to_clob(l_Data_json_clob);--put json result to clob
dbms_output.put_line(dbms_lob.substr( l_Data_json_clob, 255, 1));--correct json - more then one character
l_Data_json.put('RESULT', 1);--put one number in json value
l_Data_json.to_clob(l_Data_json_clob);--put json result to clob
dbms_output.put_line(dbms_lob.substr( l_Data_json_clob, 255, 1));--again correct json but with number instead of string
end;
You will see that for some reason first json value is empty. We noticed that it is happening only if json value is single character. Is there any workaround for this behavior?
Thank you

Answer 1

After some debugging I found that the bug is in JSON_PRINTER.ppString. The correct code should be:
procedure ppString(elem json_value, buf in out nocopy clob, buf_str in out nocopy varchar2) is
offset number := 1;
v_str varchar(5000 char);
amount number := 5000; /*chunk size for use in escapeString. Maximum escaped unicode string size for chunk may be 6 one-byte chars * 5000 chunk size in multi-byte chars = 30000 1-byte chars. Maximum value may be 32767 1-byte chars */
begin
add_to_clob(buf, buf_str, case when elem.num = 1 then '"' else '/**/' end);
if(elem.extended_str is not null) then /*clob implementation*/
while(offset <= dbms_lob.getlength(elem.extended_str)) loop
dbms_lob.read(elem.extended_str, amount, offset, v_str);
if(elem.num = 1) then
add_to_clob(buf, buf_str, escapeString(v_str));
else
add_to_clob(buf, buf_str, v_str);
end if;
offset := offset + amount;
end loop;
else
if(elem.num = 1) then
while(offset**<=**length(elem.str)) loop
v_str:=substr(elem.str, offset, amount);
add_to_clob(buf, buf_str, escapeString(v_str));
offset := offset + amount;
end loop;
else
add_to_clob(buf, buf_str, elem.str);
end if;
end if;
add_to_clob(buf, buf_str, case when elem.num = 1 then '"' else '/**/' end || newline_char);
end;