Creating a dependency tree (\RequirePackage) for packages used in my document

Question

Is there a way of creating a dependency tree for packages \RequirePackageing each other for those packages used in my document, ideally with the respective required options and version numbers? Are there any tools or packages for this purpose? This is very important for debugging package options conflicts (see "Package options and \RequirePackage: order of commands and option conflicts?"; see also "What are best practices for package authors to deal with package conflicts?").

For example, I don't need to load graphicx explicitly because dtklogos (which I'm using) already requires/loads it. In fact graphicx also requires/loads graphics and also keyval, which is incidentally also required/loaded by microtype. Etc. I would like to give an example involving package option conflicts, but as the relevant dependencies are cumbersome to figure out and debug, no example is on my mind right now (I've bumped into several, but since they didn't compile, I abandoned them and have forgotten about them); this is one thing this question can actually help to address.

Answer 1

I agree with Joseph that you should always explicitly require any package that you need, regardless of whether any other package has already loaded it, but to answer your question about logging the dependency tree, one can hook into \@onefilewithoptions like so (this is better than just hooking \RequirePackage as it also hooks classes etc):

\errorcontextlines=\maxdimen

% begin code to log calls to \@onefilewithoptions (http://tex.stackexchange.com/questions/99723/creating-a-dependency-tree-requirepackage-for-packages-used-in-my-document)
\makeatletter
\def\@log@onefilewithoptions@{}% this will store the file tree
\def\@log@onefilewithoptions@delim{^^J}%
\def\@log@onefilewithoptions#1[#2][#3]#4{% our hook
    \ifx\@currnamestack\@empty
        \def\@log@onefilewithoptions@tmp{.}%
    \else
        \edef\@log@onefilewithoptions@tmp{\expandafter\@parse@curnamestack\@currnamestack\@nil}%
    \fi
    \expandafter\g@addto@macro\expandafter\@log@onefilewithoptions@\expandafter{\@log@onefilewithoptions@tmp}%
    \edef\@log@onefilewithoptions@tmp{#4[#2]{#1}[#3]\@log@onefilewithoptions@delim}%
    \expandafter\g@addto@macro\expandafter\@log@onefilewithoptions@\expandafter{\@log@onefilewithoptions@tmp}%
}
\def\@parse@curnamestack#1#2#3#4\@nil{%
    |%
    \@log@onefilewithoptions@ifblank{#4}{%
        +%
    }{%
        \@parse@curnamestack#4\@nil
    }%
}
\newcommand{\typeoutonefilewithoptionstree}{\typeout{@onefilewithoptions tree follows:\@log@onefilewithoptions@delim\@log@onefilewithoptions@ end @onefilewithoptions tree.}}
% display the tree at end document (for demonstration purposes)
\AtEndDocument{\typeoutonefilewithoptionstree}%
% patch the original to invoke our hook first, and to show the tree if there's an option clash
\def\@onefilewithoptions#1[#2][#3]#4{%
  %added by cyberSingularity
  \@log@onefilewithoptions{#1}[#2][#3]{#4}%
  %end addition
  \@pushfilename
  \xdef\@currname{#1}%
  \global\let\@currext#4%
  \expandafter\let\csname\@currname.\@currext-h@@k\endcsname\@empty
  \let\CurrentOption\@empty
  \@reset@ptions
  \makeatletter
  \def\reserved@a{%
    \@ifl@aded\@currext{#1}%
      {\@if@ptions\@currext{#1}{#2}{}%
        {%added by cyberSingularity
        \typeout{Option clash for \@cls@pkg\space #1. To help,}%
        \typeoutonefilewithoptionstree
        %end addition
        \@latex@error
            {Option clash for \@cls@pkg\space #1}%
            {The package #1 has already been loaded
             with options:\MessageBreak
             \space\space[\@ptionlist{#1.\@currext}]\MessageBreak
             There has now been an attempt to load it
              with options\MessageBreak
             \space\space[#2]\MessageBreak
             Adding the global options:\MessageBreak
             \space\space
                  \@ptionlist{#1.\@currext},#2\MessageBreak
             to your \noexpand\documentclass declaration may fix this.%
             \MessageBreak
             Try typing \space <return> \space to proceed.}}}%
      {\@pass@ptions\@currext{#2}{#1}%
       \global\expandafter
       \let\csname ver@\@currname.\@currext\endcsname\@empty
       \InputIfFileExists
         {\@currname.\@currext}%
         {}%
         {\@missingfileerror\@currname\@currext}%
    \let\@unprocessedoptions\@@unprocessedoptions
    \csname\@currname.\@currext-h@@k\endcsname
    \expandafter\let\csname\@currname.\@currext-h@@k\endcsname
              \@undefined
    \@unprocessedoptions}
    \@ifl@ter\@currext{#1}{#3}{}%
      {\@latex@warning@no@line
         {You have requested,\on@line,
          version\MessageBreak
            `#3' of \@cls@pkg\space #1,\MessageBreak
          but only version\MessageBreak
           `\csname ver@#1.\@currext\endcsname'\MessageBreak
          is available}}%
    \ifx\@currext\@clsextension\let\LoadClass\@twoloadclasserror\fi
    \@popfilename
    \@reset@ptions}%
  \reserved@a}
% borrowed from etoolbox (don't really want to load it just for this)
\newcommand{\@log@onefilewithoptions@ifblank}[1]{%
  \etb@ifblank@i#1&&\@secondoftwo\@firstoftwo:}
\long\def\etb@ifblank@i#1#2&#3#4#5:{#4}
\makeatother
% end code to log calls to \@onefilewithoptions



% real document begins
\documentclass[a4paper]{article}
\usepackage{graphicx}
\usepackage{keyval}
%\usepackage{tikz}% uncomment this to get an option clash on the next line
\usepackage[svgnames]{xcolor}

\begin{document}
    See console output or log file.
\end{document}

Now, when you get an option clash, you should get a dump of the dependency tree just before the error.

Also, the dependency tree is always shown \AtEndDocument.

Note that in both cases, one needs to examine the console or log output, which will contain something like this:

@onefilewithoptions tree follows:
.cls[a4paper]{article}[]
.sty[]{graphicx}[]
|+sty[]{keyval}[]
|+sty[]{graphics}[]
||+sty[]{trig}[]
||+sty[]{infwarerr}[2007/09/09]
||+sty[]{ltxcmds}[2010/12/07]
.sty[]{keyval}[]
.sty[svgnames]{xcolor}[]
end @onefilewithoptions tree.

Hopefully this is easy enough to read.

Answer 2

While as indicated in comments I'd recommend simply requiring those packages you use directly, the idea of a 'tree' of package dependencies has been addressed for LaTeX2e in the pkgloader package: see Automated management of package options and loading order) for more on this. As described in the package documentation, the idea is that you give the list of packages you want to use in any order and it then 'sorts out' the dependency tree.