I have met a use case that chardet detected the file as big5, but it can't be converted by iconv totally, after some searching I found it's big5-2003 with some characters that aren't in big5. See attachment.

Since big5-2003 is compatible with big5 and with more characters, I guess it's better to use big5-2003 instead of big5, and likewise the GB18030 and GB2312

similar with issue #94

1.txt