Figure referencing broken by pandoc 1.17 TeX writer

[tomduck]

Pandoc 1.17's TeX writer uses image attributes to introduce figure labels. Unfortunately, the TeX being written is fundamentally incorrect, and this breaks referencing -- the reason why labels exist.

Here is a basic demo file (reftest.md):

![A big dot.](dot.png){#fig-1}

This is a reference to Figure \ref{fig-1}.

Compile it as follows (you will need to provide your own dot.png):

$ pandoc reftest.md -o reftest.pdf

View reftest.pdf and notice that the Figure number is missing in the reference. A look at the generated TeX ($ pandoc reftest.md -o reftest.tex) shows why:

\begin{figure}[htbp]
\centering
\includegraphics{dot.png}
\caption{A big dot.}
\end{figure}
\label{fig-1}

This is a reference to Figure \ref{fig-1}.

The \label should be inside the figure environment, and preferably in the \caption. It does not work at all when written outside of thefigure environment.

I believe this was the patch that introduced the bug.

[tomduck]

Thank you, @jgm.