Figure captions with citations fail in building PDF

[astonzhang]

Describe the bug

Figure captions with citations fail in building PDF. Here is an example (note that :citet: is an alias of :cite:t:):

Input ipynb:

Output tex:

When compiling PDF from this tex, the following error shows up:

How to Reproduce

$ git clone -b sphinx-latex https://github.com/d2l-ai/d2l-en.git
$ cd d2l-en
$ vi static/post_latex/main.py # Comment out my hack https://github.com/d2l-ai/d2l-en/blob/sphinx-latex/static/post_latex/main.py#L141
$ pip install d2lbook
$ d2lbook build pdf  # The output pdf should be at _build/pdf

Expected behavior

As a hack for this issue, I post-process this tex file. So the processed tex has a \protect and becomes:

Then the output PDF is:

Your project

https://github.com/d2l-ai/d2l-en/ and https://github.com/d2l-ai/d2l-book

Screenshots

No response

OS

Linux

Python version

3.8

Sphinx version

5.1.1

[mcmtroffaes]

Thanks for the detailed report, and apologies for the late reply - I've been on vacation. Using \protect is indeed the correct solution, and it would be possible to patch sphinxcontrib-bibtex so it always outputs \protect\hyperlink{...}. However I'm wary of any implications of using \protect everywhere for these hyperlinks - I don't understand enough about the robust/fragile system to know whether or not it will break something.

I'll close this as a duplicate of #276 - there you can find one idea for a solution (using the etoolbox package), but so far it doesn't work. Feel free to chime in there if you have further ideas.