Error: Patching 'ifthen' package failed

[merkste]

Hi,
since a couple of days I get the following error when compiling a document:

./main.tex:25: Package biblatex Error: Patching 'ifthen' package failed

I was not able to figure out the reason yet, but I suspect a recent TeXLive update introduces an incompatibility. Is this issue already known?

[moewew]

Oh dear, that does not sound good. I'm using MikTeX so I'm a little bit behind with updates and have for example not yet received the new Dec. 2018 LaTeX format and I'm not seeing any warnings. Can you reproduce this issue with any document or do you have to do something specific? In the latter case could you be so kind to show us a short example document that reproduces the warning please? It would help greatly if you could also upload the complete .log file of the example LaTeX run.

[merkste]

It turns out, that pdfx is to blame:

\documentclass[11pt]{letter}

%%% PDF/A
\RequirePackage[a-1b]{pdfx}

\usepackage{biblatex}

\begin{document}
Lorem Ipsum
\end{document}

Reverting to pdfx to 1.5.84 fixes the problem.

[moewew]

Ah thank you, that helps a lot. I'll try to find out what changed in pdfx 1.6 (https://tug.org/pipermail/tex-live-commits/2018-December/008057.html)

[merkste]

... and I just contacted the authors of pdfx. =)

[moewew]

I have no idea what is going on here, but it does not seem to be a biblatex issue.

Take the following MWE

\documentclass{article}

\usepackage[a-1b]{pdfx}
\usepackage{ifthen}
\show\ifthenelse
\begin{document}
Lorem Ipsum
\end{document}

With pdfx 1.5.84 the \show command gives > ifthenelse=\long macro: and then the lengthy definition of the macro. But with 1.6 I just get > \ifthenelse=undefined. even though I have just loaded ifthen.

[moewew]

As a temporary workaround you can try to load the package ifthen before pdfx. That made the error go away for me, but I'm not sure if everything will work as expected.

\documentclass[11pt]{letter}

\usepackage{ifthen}
\usepackage[a-1b]{pdfx}
\usepackage{biblatex}

\begin{document}
Lorem Ipsum
\end{document}

Likewise it helped to load biblatex before pdfx, but I'm not sure about the recommended loading order here. On a quick look at the pdfx documentation I could not find anything about recommended loading order. The fact that pdfx loads hyperref makes me think it should be late, but I'm not sure about the workings of the rest of the package.

Please let us know when you hear back from the pdfx developers.

[u-fischer]

pdfx loads xmpincl (which then loads ifthen) inside a group:

\begingroup
%% override the \ifpdf  check of  xmpincl  package
\ifxetex
 \pdftrue
\else\ifluatex
 \pdftrue
\fi\fi
\RequirePackage{xmpincl}
....

This is naturally completly wrong ...

[moewew]

@u-fischer Thank you very much for digging into this. I guess it would be good to contact Ross Moore (is he the maintainer now?) about this. Have you already done this? Otherwise I'll send off a quick mail pointing him to this thread.

[merkste]

I've already contacted him and will point him to this thread. Thank you all for your investigation. I'd never found this myself.

[moewew]

For now one of the workarounds that stay closest to the requirement to load pdfx as early as possible is probably

\documentclass[11pt]{letter}

\usepackage{ifthen}
\usepackage[a-1b]{pdfx}

\usepackage{biblatex}

\begin{document}
Lorem Ipsum
\end{document}

that way we only load one small-ish package before pdfx (and one that pdfx would load anyway - by proxy) and everything else can remain as is.

Question on TeX.SX: https://tex.stackexchange.com/q/465977/35864

@merkste OK, thanks for taking care of that.

[TheTeXnician]

Version 1.6.1 (2018/12/22) is on CTAN and does contain the following change log entry: "Fixed issue with ifthen package", so this issue can be closed.

[moewew]

Thanks for the heads up. According to https://tug.org/pipermail/tex-live-commits/2018-December/008211.html the new code is

%%----------------------------------------------------------------------
%%  2018-12-16:   xmpincl  needs the  ifthen  package
%%  it should be loaded outside the grouping, else  biblatex  may barf
%%
\RequirePackage{ifthen}
\begingroup
%% override the \ifpdf  check of  xmpincl  package, inside the grouping
 \pdftrue
 \RequirePackage{xmpincl}

and still loads xmpincl inside a group (which I find problematic), but our woes are alleviated by loading ifthen explicitly outside that group.

I haven't tested v1.6.1 yet, because it hasn't arrived in MikTeX yet, but I trust this should solve this issue.

[u-fischer]

One really wonder about this \begingroup stuff - breaking other packages like this isn't right. xmpincl is so short that it should easy to extract the needed code for xetex and so avoid to use such tricks. But beside this the update seems to solve the problem for biblatex.

[moewew]

pdfx v1.6.1 made it to MikTeX this morning. That means that the fixed version is now in both big TeX distributions. The MWEs from above all compile fine now.

Thanks to everyone involved for your help. Have a good 2019. 🎆

[merkste]

@moewew thanks for all your help!