issue_comments

Once I've got the plugins mechanism stable and people start releasing plugins it would be useful to have a dedicated Trove classifier on PyPI for Datasette plugins - Framework :: Datasette for example.

This would help me build a Datasette equivalent of the http://plugincompat.herokuapp.com/ site, which works by scanning PyPI for items with the Framework :: Pytest classifier:

https://github.com/pytest-dev/plugincompat/blob/8bdf1a6fb82807091ece0c68c196103ee8270194/update_index.py#L52-L53

It looks like the mechanism for requesting new PyPI classifiers is to file a ticket against warehouse, like these ones: https://github.com/pypa/warehouse/issues/3570 and https://github.com/pypa/warehouse/issues/2881

I built a prototype of the convert_units() custom SQL function as a plugin over in https://github.com/simonw/datasette/issues/14#issuecomment-381446511

Here's a demo of the convert_units() SQL function I prototyped in f2720b0c6b7172ebe88

Tox is a good example of a project that uses pluggy in the way I want to use it (function hooks rather than classes): https://github.com/tox-dev/tox/blob/master/tox/hookspecs.py

Datasette 1.0 will be the release of Datasette that attempts to provide a stable plugin API: https://github.com/simonw/datasette/milestone/7

There's a lot of work to be done before then, but as a starting point I'm going to support two very simple extension mechanisms:

• Template system plugins - where the hook gets passed the Jinja environment and can freely register new template tags and filters
• SQLite connection plugins - where the hook gets passed a new SQLite connection and can register custom SQLite functions

The template system hook will go near here:

https://github.com/simonw/datasette/blob/efbb4e83374a2c795e436c72fa79f70da72309b8/datasette/app.py#L1225-L1228

The SQLite connection hook will go near here:

https://github.com/simonw/datasette/blob/efbb4e83374a2c795e436c72fa79f70da72309b8/datasette/app.py#L1094-L1098

These two feel simple enough that I'm not worried that I might design an API that I later regret.

I started a thread on Twitter asking people for good examples of Python projects with a strong plugin ecosystem: https://twitter.com/simonw/status/985377670388105216

The most impressive example that came back was pytest - which now has nearly 400 plugins: https://plugincompat.herokuapp.com/

The pytest plugin infrastructure is available as an independent package called pluggy - which appears to offer everything I need for Datasette. I'm going to give that a go and see how well it works: https://pluggy.readthedocs.io/en/latest/

I suspected this would cause some test failures, but I'll wait for opinions before attempting to fix them.

I think I found a bug. I tried to sort by middle initial in my salaries set, and many middle initials are null. The next_url gets set by Datasette to:

http://localhost:8001/salaries-d3a5631/2017+Maryland+state+salaries?_next=None%2C391&_sort=middle_initial

But then None is interpreted literally and it tries to find a name with the middle initial "None" and ends up skipping ahead to O on page 2.