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In the mediagoblin repository, there's a sample plugin under mediagoblin/plugins/sampleplugin that you can use to get started with plugin creation. The simplest way to get up and running is to

  1. Follow HackingHowto#How_to_set_up_and_maintain_an_environment_for_hacking_with_virtualenv to set up a local virtualenv mediagoblin instance
    • run it with ./ so you get debug output (if you run celeryd separately, you won't see from stuff run in celery tasks)
  2. cp -r mediagoblin/plugins/sampleplugin mediagoblin/plugins/myplugin (where "myplugin" is your plugin name)
  3. cp mediagoblin.ini mediagoblin_local.ini
  4. edit mediagoblin_local.ini and add [[mediagoblin.plugins.myplugin]] under the [plugins] section to enable your plugin

Now you can look at e.g. other core or non-core plugins for inspiration. See Available Plugins for non-core plugins.

The way you change things in plugins is by use of hooks. At certain points in the mediagoblin code, a function will say "run all hooks with name XYZ", and if you've defined a hook with such a name in a plugin you've enabled, it'll get run there. The documentation on Plugin API is your friend for defining hooks. The sample plugin shows a use of the 'setup' hook.

Note: templates are hooked with a call to pluginapi.register_template_hooks, instead of adding to the hooks variable.

Making an installable plugin

If you followed the steps above, you can use your plugin by copying it into the plugins folder; however, to get a plugin that is easily installable by users (e.g. with pip install myplugin), it should have a certain folder layout.

A good example is the RDFa plugin. This uses a file to install the files under the mediagoblin_rdfa folder into the lib/ folder of your mediagoblin installation. If you've checked out both mediagoblin and mg-rdfa in the same folder, e.g. ~/src/, you can do

cd ~/src/mg-rdfa/
../mediagoblin/bin/python build
../mediagoblin/bin/python install

to install it to your mediagoblin instance.

The file layout of the repo is:

The file defines an option include_package_data=True, which makes it read the file; contains rules for which files to include when installing. In this case, rule recursive-include mediagoblin_rdfa *.html makes it include the HTML template file (and any other you put under mediagoblin_rdfa), retaining the folder layout.