Using custom labelprefixes and \printbibtabular return [0] for all citations in text

[yosata]

Describe the bug
Using \printbibtabular with custom label prefixes return [0] when cited in the text. Replacing \printbibtabular by \printbibliography solves the citation issue, but obviously removes the reference table.

To Reproduce
Below a minimal example that reproduces the behavior:

\documentclass{article}
\usepackage[style=numeric, backend=biber, date=short, defernumbers=true]{biblatex}
\usepackage{biblatex-ext-tabular}
\usepackage{longtable}

\addbibresource{biblatex-examples.bib}

% Defines the function that prints references in a table
\defbibtabular{bibtabular}{%
    \begin{center}
        \setlength\LTleft{0pt}
        \setlength\LTright{0pt}
        \begin{longtable}{@{\extracolsep{\fill}}|c|p{0.7\linewidth}|c|@{}}
            \hline \textbf{RD Nr} & \textbf{Document Title} & \textbf{Date}\endhead 
            \hline
            }
            {
            \hline
        \end{longtable}
    \end{center}}
    {
    \anchorlang{%
      \printtext[labelnumberwidth]{%
      \printfield{labelprefix}%
      \printfield{labelnumber}}}
  & \plainlang{\usebibmacro{title}} \plainlang{\usebibmacro{author}}
  & \plainlang{\printdate}\\ \hline}

\begin{document}
\cite{worman,geer,nussbaum,companion}

\newrefcontext[labelprefix=RD]
\printbibtabular

\end{document}

Expected behaviour
I would expect that the reference labels follow the prefixes that I defined. For example, \cite{worman} should print "[RD4]".

Output
PDF output using \printbibtabular:

Replacing \printbibtabular by \printbibliography gives the proper citation labels, but removes the tabular bibliography:

Additional context
I'm trying to create a template for some technical documentation. In this template is a requirement for two types of bibliographies (Applicable Documents and Reference Documents), both in tabular format. I'm using \printbibtabular to print these in a tabular format, both with different label prefixes. The tables look fine. However, when citing in the document text, instead of returning the proper label (e.g. [RD1], [AD3], etc.) it returns [0] each time.
I'm not sure that it matters, but I'm using Overleaf to write my LaTeX documentation.

Things I've tried

• Replacing \printbibtabular by \printbibliography solves the citation issue, but removes the reference table and replaces it with the normal reference list.
• Setting defernumbers=false in the biblatex arguments removes the custom prefixes when citing in the text. The label prefixes are still added in the table. This is not ideal. The numeric citations work fine in this case, except that they do not reset when defining a second type of references.

[moewew]

Thank you very much for reporting this issue.

I'm not quite sure yet how to fix this at the biblatex-ext end, but I think I know why it happens and I can offer you a workaround for your document.

The problem here is that we need to set the 'default refcontext' for the entries that appear in the tabular bibliography. In \printbibliography that happens directly when the items are printed. In \printbibtabular different bits of the entry can be printed with different commands. Only \driver sets the default refcontext. Since your example does not have a \driver call, the default refcontext is never set. biblatex-ext-tabular needs to be changed to make sure that the refcontext is always set no matter which printing commands are used. But I'm not quite sure how exactly we should do this.

For now a workaround for your document is to manually initiate setting the default refcontext.

\documentclass{article}
\usepackage[style=numeric, backend=biber, date=short, defernumbers=true]{biblatex}
\usepackage{biblatex-ext-tabular}
\usepackage{longtable}

\addbibresource{biblatex-examples.bib}

\makeatletter
\def\fixextblx@setrefcontext{%
  \expandafter\blx@setdefaultrefcontext\expandafter{\abx@field@entrykey}}

\defbibtabular{bibtabular}
  {\begin{center}
     \setlength\LTleft{0pt}
     \setlength\LTright{0pt}
     \begin{longtable}{@{\extracolsep{\fill}}|c|p{0.7\linewidth}|c|@{}}
       \hline \textbf{RD Nr} & \textbf{Document Title} & \textbf{Date}\endhead 
       \hline}
  {    \hline
     \end{longtable}
   \end{center}}
  {  \anchorlang{%
       \fixextblx@setrefcontext
       \printtext[labelnumberwidth]{%
         \printfield{labelprefix}%
         \printfield{labelnumber}}}
   & \plainlang{%
       \usebibmacro{title}%
       \newunit
       \usebibmacro{author}}
   & \plainlang{\printdate}\\ \hline}
\makeatother

\begin{document}
\cite{worman,geer,nussbaum,companion}

\newrefcontext[labelprefix=RD]
\printbibtabular

\end{document}

[moewew]

This bug should be fixed with 06dd359, where we make sure to always set the default refcontext independent of the tabular wrappers you use. v0.12b was sent off to CTAN a few minutes ago and should land in TeX Live and MikTeX in the next days.

[yosata]

Thanks for the quick response! Your workaround did indeed fix the problem.

[moewew]

Version 0.12b with the fix is available in both MikTeX and TeX Live now. The MWE from the first post now produces the expected output.

Overleaf don't update their systems continuously, so you will need the workaround proposed on Overleaf until they offer TeX Live 2021 or later with updates from today or later (and you switch your document to that new system).