pgfkeys ".estore in" handler does not work as expected

Question

In the process to migrate from (x)keyval to pgfkeys, I realized that .estore in was not expanding my command properly.

Here is my minimal working example:

\documentclass{report}

\usepackage{pgfkeys}
\makeatletter

\newif\if@wgetdoc@title@ownpage
\pgfkeys{
    /wgetdoc/title/.cd,
    maintitle/.estore in=\@wgetdoc@title@maintitle,
    subtitle/.estore in=\@wgetdoc@title@subtitle,
    author/.estore in=\@wgetdoc@title@author,
    filename/.estore in=\@wgetdoc@title@filename,
    ownpage/.is if=@wgetdoc@title@ownpage
}

\renewcommand{\title}[1][]{%

    \pgfqkeys{/wgetdoc/title}{#1}

    \@ifundefined{@wgetdoc@title@filename}{

        \@ifundefined{@wgetdoc@title@maintitle}{
            \ClassError{wgetdoc}{You did not specify a main title}{}
        }{}

        \@ifundefined{@wgetdoc@title@maintitle}{
            \ClassError{wgetdoc}{You did not specify a main title}{}
        }{}

        \ifx\@wgetdoc@title@maintitle\@empty
            \ClassError{wgetdoc}{The main title you specified is empty}{}
        \fi

        % Custom horizontale rule only local to this environment
        \newcommand{\@wgetdoc@title@hrule}{\rule{\linewidth}{1mm}}

        \if@wgetdoc@title@ownpage
            \begin{titlepage}
                \begin{center}

                    \@wgetdoc@title@hrule%
                    \vspace{0.4cm}

                    {\Huge\textbf{\@wgetdoc@title@maintitle}\par}%

                    \vspace{0.4cm}%
                    \@wgetdoc@title@hrule

                    \@ifundefined{@wgetdoc@title@subtitle}{}{
                        \vspace{1.5cm}
                        {\Large{\@wgetdoc@title@subtitle}\par}%
                    }

                    \@ifundefined{@wgetdoc@title@author}{}{
                        \vspace*{\fill}
                        {\emph{\GetTranslation{author}: \@wgetdoc@title@author}\par}%
                    }

                \end{center}
            \end{titlepage}%
        \else
            \begin{center}
                {\huge\textbf{\@wgetdoc@title@maintitle}\par}
                \@ifundefined{@wgetdoc@title@subtitle}{}{
                    {\large{\@wgetdoc@title@subtitle}\par}%
                }
            \end{center}
            \@ifundefined{@wgetdoc@title@author}{}{
                {\emph{\GetTranslation{author}: \@wgetdoc@title@author}\par}%
            }
            \@wgetdoc@title@hrule%
        \fi

    }{
        \IfFileExists{\@wgetdoc@title@filename}{%
            \includepdf[pages={1}]{\@wgetdoc@title@filename}%
            \ClassInfo{wgetdoc}{\@wgetdoc@title@filename has been used as title page. Any other argument have been discarded.}{}
        }{%
            \ClassError{wgetdoc}{You specified \@wgetdoc@title@filename as filename for the page title, but it could not be found.}{}
        }
    }
}

\makeatother

\begin{document}

\title[maintitle=hello world, ownpage, subtitle=hello world]

Hello world

\end{document}

As soon I remove my formatting and type

\title[maintitle=hello world, ownpage, subtitle=hello world]

instead of

\title[maintitle=hello world, ownpage, subtitle=hello \textsc{world}]

This is working. Could anyone explain to me why estore in is not working as expected (expanding the value before assigning it). This was working properly with xkeyval.

The error I get when I try to compile (using xelatex):

! Use of \\title doesn't match its definition.
\text@command #1->\def \reserved@a {
                                    #1}\ifx \reserved@a \@empty \let \check@...
l.88 ...d, ownpage, subtitle=hello \textsc{world}]

?

Answer 1

The .estore in handler is for cases when the value can depend on a macro that's likely to receive different values between the setting and the usage of the created macro. Such macros should be safe for full expansion.

Indeed, one has to be aware of the fact that .estore in uses \edef and several typesetting macros don't survive it: \textsc is one of them, together with all font selection macros.

With maintitle/.store in=\@wgetdoc@title@maintitle, when you do

maintitle=Hello world,

you just perform

\def\@wgetdoc@title@maintitle{Hello world}

and you need no expansion; when \@wgetdoc@title@maintitle is used, it will expand to Hello world.

It would be good if pgfkeys provided also a .protectedestore in handler, at least in a LaTeX context; alas, there is nothing like this and you wouldn't need it anyway.

---

I'd avoid all those blank lines in the code and protect end-of-lines more carefully.

Answer 2

\textsc (and many other text formatting macros) is unexpandable and causes to be processed in time which is often referred to early expansion. That's causing the problem.

If you need an expansion before the macro storing, you can use the /.expand once,/.expand twice and /.expanded handlers instead and use store in.

Also there is a bug report waiting to be fixed about /.estore in

Answer 3

Based on @egreg's answer.

So to solve the issue, I just had to use .store in instead of .estore in. This is really weird as the main purpose of the .estore in command is just to make sure things are expanded properly (cf. the pgfkeys documentation). But it appears in my use case that \url or \textsc are expanded properly even without the need to use .estore in.

If someone has a comment to make to explain why.