Spurious comma with LuaLatex, hyperxmp, hyperref and pdfa

Question

I compile the following code

\documentclass{article}
\usepackage{hyperxmp} 
\usepackage[pdfa]{hyperref} 
\usepackage{kantlipsum}
\hypersetup{
    keeppdfinfo,
    pdftitle={test},
    pdfauthor={sdaf},
    pdfapart=1,
    pdfaconformance=B,
}
\begin{document}
\kant[1]
\end{document}

and somehow I get interesting results.

I get the backtick at the beginning of the page. I need the variables in hypersetup to get rid of the warnings. When I disable the package hyperxmp it vanishes, when I remove the option pdfa it vanishes as well.

Honestly don't know how to get rid of this backtick. Following the old question didn't help either. I've share my log temporarily

Answer 1

I've asked the author of the package and his reply was:

Try loading hyperref before hyperxmp.

hyperxmp was written to hook into hyperref's argument-processing routines, which it does by rewriting some of them. When you load hyperref after hyperxmp, hyperref undoes all of hyperxmp's changes. Although hyperxmp takes great strides to function correctly in this case, every update to hyperref breaks something new in hyperxmp. I should probably just give up and issue an error message if the packages are loaded in the "wrong" order.

and running the code with

\documentclass{article}
\usepackage[pdfa]{hyperref} 
\usepackage{hyperxmp} 
\usepackage{kantlipsum}
\hypersetup{
    keeppdfinfo,
    pdftitle={test},
    pdfauthor={sdaf},
    pdfapart=1,
    pdfaconformance=B,
}
\begin{document}
    \kant[1]
\end{document}

fixes the problem. Thx for pointing out where to source of the error might be and thx for making it clear what solution should be applied!