The goal was a single page documentation on expression
One approach could have been about using
scripts/process_function_template.py and/or files in
resources/function_help/json/. As there is no link between groups and functions documented in these json files, you need to look for the relation in the source
src/core/expression/qgsexpressionfunction.cpp. You would also need to manage translations. FYI, all paths are relative to the root of the source code repo.
So, instead we’ve made the choice to use HTML generated doc for expressions from PyQGIS docs. It works for any languages
You need to install third party Python library BeautifulSoup4 into the version of Python used by QGIS. For Linux, do it with
pip install beautifulsoup4
Then, run the script
pyqgis-list-expressions.py within PyQGIS console.
As the script is generated dynamically within QGIS and we need to change the locale each time we want to generate a new lang doc, we only produced some translations. Feel free to ask in the comments for another languages.