Reliably add a label to the current section, even if the label is not placed right after the section name

Question

I have a package that would like to put a reference to a section. The package cannot put the label right after the section title, so for now it just drops a \label{sec:mysection}. The problem is that if an equation is defined before, then (using \autoref{sec:mysection}) the label points to the previous equation, not to the section.

Using \cref{sec:mysection} solves one part of the issue: the text is fine, but the link still points to the equation. Any idea how to solve that?

Any idea?

Thanks!

MWE:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}
\usepackage{hyperref}
\usepackage{cleveref}
\begin{document}
\section{My section}
With autoref, the name is bad, and the link is bad: \autoref{section:shouldbeappendixA}.\
With cleverref, the name is good, but the link is bad: \cref{section:shouldbeappendixA}.
\appendix
\section{Proofs}
Here is my appendix
\vspace{3cm}
\begin{equation}
  1+1=2
\end{equation}
\vspace{3cm}\
I would like this label to point to the heading of the current section, not to the last equation I wrote\label{section:shouldbeappendixA}. But I don't want to move the label code, because it's inserted automatically by a script.
\end{document}

EDIT 2021: Explanation of the original problem

To clarify the original problem I am having, I wrote this library which allows a user to move proofs in appendix. Basically, a user writes a code like:

\section{My section A}
\begin{thmE}[Title][end,category=sectionA]
  My first theorem
\end{thmE}
\begin{proofE}
  My first proof
\end{proofE}
\section{My section B}
\begin{thmE}[Title][end,category=sectionB]
  My second theorem
\end{thmE}
\begin{proofE}
  My second proof
\end{proofE}
\section{Appendix: proof of section A}
Here are the proofs of section A:
\printProofs[sectionA]
\section{Appendix: proof of section B}
Here are the proofs of section B:
\printProofs[sectionB]

Then, the final output will be:

Internally, the library creates one file per category (i.e. groups of proofs). This file, later included via \printProof[nameCategory], will contain for each proof in this category, something like:

\label{proofsection:prAtEndii}
\begin{proof}[Proof of \autoref{thm:prAtEndii}]\phantomsection\label{proof:prAtEndii}
  My first proof
\end{proof}

Therefore, if I have 2 libraries in the category, the included code will be:

\label{proofsection:prAtEndii}
\begin{proof}[Proof of \autoref{thm:prAtEndii}]\phantomsection\label{proof:prAtEndii}
  My first proof
\end{proof}
\label{proofsection:prAtEndiii}
\begin{proof}[Proof of \autoref{thm:prAtEndiii}]\phantomsection\label{proof:prAtEndiii}
  My third proof
\end{proof}

Then, the link to the section containing the proof is done via \autoref{proofsection:prAtEndii} or \cref{proofsection:prAtEndii} right after writing the theorem. The problem is that the label proofsection:prAtEndii may not point really to the first section because it won't be written right after the section (this is the case for the label proofsection:prAtEndiii in the above example).

One solution may be to create one more file internally containing only the labels like \label{proofsection:prAtEndii}\label{proofsection:prAtEndiii}, create another function like \addLabelToSection[nameOfCategory], and ask to the user to include it in the appendix section via something like:

\section{Appendix: proof of section A}
\addLabelToSection[sectionA]
Here are the proofs of section A:
\printProofs[sectionA]

but I don't really like this approach because the user will have to write two commands to print the proofs instead of one. Moreover, if at some point they change the name of the category while forgetting to replace the name also in the \addLabelToSection command, then the references will be missing, producing mystic errors like Can't find label proofsection:prAtEndii... which is not a great experience for the user. Is there a way to get rid of this burden?

Answer 1

This is an extended comment with one idea of what you can do; I don't have the time to code it up for you but you seem to be proficient around TeX.

The idea is basically to hook into what \label does: it prints something into the .aux file based on the value of \@currentlabel, which is set by \refstepcounter which itself is implicitly called by \section or many environments, and is modified by packages that much around such things (like \hyperref). So what you want to do is to swap out the value of \@currentlabel on the sly.

One way to do this is to patch \section with something like (untested, only to illustrate concept, and may have bugs)

\let\old@tobias@section\section
\renewcommand\section[1]{\old@tobias@section{#1}\let\tobias@stored@label\@currentlabel}

And then, when you generate your proof sections and preparing them for printing, do

\let\@currentlabel\tobias@stored@label
\label{proofsection:...}

so when you do the labeling, the most recently stored section label is actually called.

---

The code above will not work perfectly as written, since you also have to handle \thepage which is also used in constructing the labels (see How does \@currentlabel work? How does it connect to sectioning commands / headings?).

The design of LaTeX's \label really is intended to put a label exactly where it is sitting in your source code, with the most recently \refsteped counter. Solving the issue with the latter is relatively easy; you can cheat by \refsteping the appropriate counter yourself or muck around with \@currentlabel like suggested above. Convincing LaTeX that your label really doesn't want to be where you put it, but elsewhere on a different page, will take more work, and can interact funnily with other ref packages (e.g. hyperref).