A Sphinx extension which allows :param: directives within Python documentation to be linkable.
This is an experimental, possibly-not-useful extension that's used by the SQLAlchemy project and related projects.
Just turn it on in conf.py:
extensions = [ 'sphinx_paramlinks', # your other sphinx extensions # ... ]
The paragraph link involves a short stylesheet, to allow the links to be visible when hovered. This sheet is called sphinx_paramlinks.css and the plugin will copy it to the _static directory of the output automatically. The stylesheet is added to the css_files list present in the template namespace for Sphinx via the Sphinx.add_stylesheet() hook.
:param: directives within Sphinx function/method descriptions will be given a paragraph link so that they can be linked to externally.
A new text role :paramref: is added, which works like :meth:, :func:, etc. Just append the parameter name as an additional token:
The directive makes use of the existing Python role to do the method/function lookup, using the :obj: role; then the parameter name is applied separately to produce the final reference link.
The paramlinks are also added to the master index as well as the list of domain objects, which allows them to be searchable through the searchindex.js system. (new in 0.3.0)
The extension was developed on Python 2.7, but is compatible with at least Python 3.3 as well. It contains one u'' literal - these are supported again as of Python 3.3.
I've tried very hard to make as few assumptions as possible about Sphinx and to use only very simple public APIs, so that architectural changes in future Sphinx versions won't break this plugin. To come up with this plugin I spent many hours with Sphinx source and tried many different approaches to various elements of functionality; hopefully what's here is as simple and stable as possible based on the current extension capabilities of Sphinx.
One element that involves using a bit of internals is the usage of the sphinx.domains.python.PyXRefRole class, which is currently the Sphinx class that defines roles for things like :meth:, :func:, etc. The object is used as-is in order to define the :paramref: role; the product of this role is later transformed using standard hooks.
Another assumption is that in order to locate the RST nodes Sphinx creates for the :param: tags, we look at nodes.strong, assuming that this is the type of node currently used to render :param: within RST. If this changes, or needs to be expanded to support other domains, this traversal can be opened up as needed. This part was difficult as Sphinx really doesn't provide any hooks into how the "Info Field List" aspect of domains is handled.
Overall, the approach here is to apply extra information to constructs going into the Sphinx system, then do some transformations as the data comes back out. This relies on as little of how Sphinx does its thing as possible, rather than going with custom domains and heavy use of injected APIs which may change in future releases.
Future Enhancements / Missing Features
The extension currently does only :param: elements within the Python role, but could also be expanded to support other Python role elements such as :returns:, :raises:, etc., and perhaps also could be made to support similar features in other roles.
Another area that's not addressed at all is search. While the params here are linked, these objects are currently not part of the search index Sphinx creates in any usable way. I don't know what would be involved to make that work.