[Tex/LaTex] Automated management of package options and loading order

incompatibilitypackage-options

This question led to a new package:
pkgloader(CTAN, Github)

LaTeX package conflicts are a common source of frustration: (1) (2) (3) (4) (5) (6). To quote Freek Dijkstra:

Package conflicts in LaTeX are a hell.

I've been looking around, but I don't think anyone has worked on what would seem, to me, the obvious solution: a package which automates conflict resolution for LateX packages.

As it happens, my PhD research (Delta Modeling) matches this problem closely, so I've made a quick start on that package and I would like some feedback on the idea.

The current version is temporarily stored in an SVN branch for another package. It depends on the l3graph package I'm working on, which is not ready for CTAN yet. The l3graph package offers a graph datastructure for expl3 with facilities for detecting cycles and working with the transitive closure/reduction and topological order of graphs.

Package Description

The pkgloader package offers tools for resolving conflicts, and is backed by a database of known resolutions. For the average user, everything would just work. The user interface looks like this:

\documentclass{article}

\usepackage{pkgloader}

% List packages in any order you please
\usepackage{xltxtra}
\usepackage[xetex]{graphicx}

\LoadPackagesNow

\begin{document}
\end{document}

By redefining \usepackage (and friends), pkgloader gathers the list of packages (with options) that the user wants to load, then loads them in the right order at the \LoadPackagesNow command. The package order above (needs XeTeX) would immediately cause an error if not for pkgloader.

It is able to prevent the problem because I've already included a modest list of package-ordering rules:

\Load {fancyhdr} before {hyperref}
\Load {fncychap} before {hyperref}
\Load {float}    before {hyperref}
\Load {hyperref} before {algorithm}
\Load {amssymb}  before {xunicode}
\Load {amssymb}  before {xltxtra}
\Load {graphicx} before {xltxtra}
\Load {graphicx} before {fontspec}
\Load {caption}  before {subfig}

These can also be added manually.

Potential Features

Fixing the package loading order is only the first (and simplest) step. With a bit of extra work we could add features like the following:

A package ordering rule like: \Load {cleveref} late (or early)
Facilities for package authors to include their own resolutions in a uniform way
Automatic detection of cycles within the rules
Accumulating and combining package options, with specific rules per package
Adding extra 'glue code' to make two other packages behave (if they're both being loaded)
Automatically resolving pretty much every conflict listed on Freek's page.
For conflicts that cannot (yet) be resolved, at least show an error message rather than let things go wrong at a later stage.

Question: What prior work is there?

Specifically:

Is there already another package that does (something like) this?
Are there any specific pitfalls I should be aware of?
Other than Freek's page, is there any kind of comprehensive list of known conflicts and resolutions?

I think a package like this has the potential to be very useful to a lot of people, if I do this right. A package like this will have a very wide scope. I don't want to step on anyone's toes, so please help me do this right.

I'd be happy to collaborate with the community on this – any feedback is welcome, so contact me if you're interested.

Best Answer

The first version of the pkgloader package has been released! Based on all of the useful comments above, and my own (re)search, I feel safe to answer my own individual questions as follows:

Is there already another package that does (something like) this?

No. The closest that has been suggested is scrlfile, and, frankly, it's not all that close. Also, others have since asked for this kind of package, just like I did.

Are there any specific pitfalls I should be aware of?

The comments above name a couple of important issues that need to be taken into account.

Both options and minimal version need to be tracked for each package request.
There is not always one correct package loading order. Sometimes both choices are valid, even if they yield different results. This may just be a matter of user-preference.
Sometimes ordering two packages is not enough, but some 'glue code' needs to be run to make two packages work together.

There are probably plenty of other issues. But as for specific pitfalls, I haven't found any that I haven't been able to work around. As always, I'm open to new information (which should go to the Github issue tracker, please).

Other than Freek's page, is there any kind of comprehensive list of known conflicts and resolutions?

It doesn't seem so. To equip pkgloader with a good set of rules, the following should be done:

Encode the problems and solutions on Freek's page into pkgloader rules.
Search tex.SE for conflict reports and encode those.
Once pkgloader has been thoroughly tested and is trusted by the community, new conflicts (and resolutions) posted to tex.SE should be reported to the pkgloader issue tracker.

Eventually, the pkgloader developers (for now, just me) will need to maintain a comprehensive list.

As mentioned in the release-notes, I wouldn't yet trust the package blindly to handle my package loading needs, although I haven't yet found any bugs. A suite of unit-tests needs to be written, additional features need to be implemented and a useful set of rules needs to be defined.

Please feel free to contribute! Just use the Github issue tracker, or contact me personally.

Related Solutions

[Tex/LaTex] minted’s listing environment with hyperref and caption package together

As you already have found out the problem occurs every time the hyperref package will be loaded prior to the minted package. This is happening here:

The hyperref package will be loaded. It does not detect the float package (because the float package is not loaded yet), and therefore it does not patch the float package code.
The minted package will be loaded which loads the float package, and does a \newfloat.
The caption package will be loaded. It does detect the float and hyperref packages, and assumes that the float package code was patched by hyperref. But this assumtion is false in this case.

So as solution you could load the float package prior to the hyperref package and the minted package after the hyperref package - which BTW is the correct load order anyway, see hyperref's README for details.

\documentclass{report}

% it's all in the order of the imports

% this one is the correct one:

% 1. Load the float package
\usepackage{float}

% 2. Load the hyperref package; hyperref will patch the float package
\usepackage{hyperref}

% 3. Load the minted package which will use the patched \newfloat now
\usepackage{minted}

% The load order of the caption package is (or should be) irrelevant now
\usepackage{caption}

\begin{document}

\chapter{test}

\clearpage

\begin{listing}[H] \mint{cl}/(car (cons 1 2))/
\caption{Example of a listing.}
\label{lst:example}
\end{listing}
\clearpage

Listing \ref{lst:example} contains an example of a listing.

\end{document}

[Tex/LaTex] Package options and \RequirePackage: order of commands and option conflicts

Basically the package is only loaded once, with the options specified at that point. Any later uses of \RequirePackage or \usepackage are silently ignored if the options specified were specified earlier, or generate an error otherwise. Normally it works to put options on \documentclass, so they are global options seen by all packages.

The help text for the option clash error suggests placing the clashing package in the global options on \documentclass but that in fact isn't very good advice. (One might consider that a latex bug). What does work is to use something like

\documentclass{article}


\PassOptionsToPackage{pdfa=true,linkbordercolor={0 0 1}}{hyperref}
\usepackage[a-1b]{pdfx}
\usepackage[pdfa=true]{hyperref}

\begin{document}
a
\end{document}

\PassOptionsToPackage doesn't actually load the package but does arrange that if it is loaded it will get those options plus any others explicitly listed when it is loaded. So if you suspect that one or more of your packages is internally loading a package and you want to make sure that it has certain options you can use this method. In the particular case of hyperref the alternative suggested in mhp's anwer is also good, avoid the package option and use the hypersetup mechanism instead. However not all packages provide a means to set options after the package is loaded in that way.