Usage

Creating plugins

If you use git in your project, install the gitpython module (pip install gitpython --dev). startplugin will determine your git user/email automatically and use it.

Create a plugin using a Django management command:

./manage.py startplugin fooplugin

This command asks a few questions, creates a basic Django app in the plugin path chosen in PluginManager.find_plugins(). It provides useful defaults as well as a setup.py/setup.cfg file.

You now have two choices for this plugin:

Static plugins

In most of the cases, you will ship your application with a few “standard” plugins that are statically installed. These plugins must be loaded after the gdaps app.

# ...

INSTALLED_APPS = [
    # ... standard Django apps and GDAPS
    "gdaps",

    # put "static" plugins here too:
    "myproject.plugins.fooplugin",
]

This plugin app is loaded as usual, but your GDAPS enhanced Django application can make use of it’s GDAPS features.

Dynamic plugins

By installing a plugin with pip, you can make your application aware of that plugin too:

pip install -e myproject/plugins/fooplugin

This installs the plugin as python module into the site-packages and makes it discoverable using setuptools. From this moment on it should be already registered and loaded after a Django server restart. Of course this also works when plugins are installed from PyPi, they don’t have to be in the project’s plugins folder. You can conveniently start developing plugins in there, and later move them to the PyPi repository.

The plugin AppConfig

Plugins’ AppConfigs must provide an inner class named PluginMeta, or a so named attribute pointing to an external class. For more information see gdaps.apps.PluginMeta.

Interfaces

Plugins can define interfaces, which can then be implemented by other plugins. The startplugin command will create a <app_name>/api/interfaces.py file automatically. It’s not obligatory to put all Interface definitions in that module, but it is a recommended coding style for GDAPS plugins:

from gdaps import Interface

@Interface
class IFooInterface:
    """Documentation of the interface"""

    __service__ = True  # is the default

    def do_something(self):
        pass

Interfaces can have a default Meta class that defines Interface options. Available options:

__service__

If __service__ = True is set (which is the default), then all implementations are instantiated directly at loading time, having a full class instance availably at any time. Iterations over Interfaces return instances:

for plugin in IFooInterface:
    plugin.do_something()

If you use __service__ = False, the plugins are not instantiated, and iterations over Instances will return classes, not instances. This may be desired for reducing memory footprint, data classes, or classes that just contain static or class methods.

for plugin in INonServiceInterface:
    print(plugin.name)  # class attribute
    plugin.classmethod()

    # if you need instances, you have to instantiate the plugin here.
    # this is not recommended.
    p = plugin()
    p.do_something()

Implementations

You can then easily implement this interface in any other file (in this plugin or in another plugin) by subclassing the interface:

from myproject.plugins.fooplugin.api.interfaces import IFooInterface

class OtherPluginClass(IFooInterface):

    def do_something(self):
        print('I did something!')

Using Implementations

You can straight-forwardly use implementations that are bound to an interface by iterating over that interface, anywhere in your code.

from myproject.plugins.fooplugin.api.interfaces import IFooInterface

class MyPlugin:

    def foo_method(self):
        for plugin in IFooInterface:
            print plugin.do_domething()

Depending on the __service__ Meta flag, iterating over an Interface returns either a class (__service__ = False) or an instance (__service__ = True), which is the default.

Extending Django’s URL patterns

To let your plugin define some URLs that are automatically detected by your Django application, you have to add some code to your global urls.py file:

from gdaps.pluginmanager import PluginManager

urlpatterns =  [
    # add your fixed, non-plugin paths here.
]

# just add this line after the urlpatterns definition:
urlpatterns += PluginManager.urlpatterns()

GDAPS then loads and imports all available plugins’ urls.py files, collects their urlpatterns variables and merges them into the global one.

A typical fooplugin/urls.py would look like this:

from . import views

app_name = "fooplugin"

urlpatterns =  [
    path("/fooplugin/myurl", views.MyUrlView.as_view()),
]

GDAPS lets your plugin create global, root URLs, they are not namespaced. This is because soms plugins need to create URLS for frameworks like DRF, etc. Plugins are responsible for their URLs, and that they don’t collide with others.

Per-plugin Settings

GDAPS allows your application to have own settings for each plugin easily, which provide defaults, and can be overridden in the global settings.py file. Look at the example conf.py file (created by ./manage.py startplugin fooplugin), and adapt to your needs:

from django.test.signals import setting_changed
from gdaps.conf import PluginSettings

NAMESPACE = "FOOPLUGIN"

# Optional defaults. Leave empty if not needed.
DEFAULTS = {
    "MY_SETTING": "somevalue",
    "FOO_PATH": "django.blah.foo",
    "BAR": [
        "baz",
        "buh",
    ],
}

# Optional list of settings that are allowed to be in "string import" notation. Leave empty if not needed.
IMPORT_STRINGS = (
    "FOO_PATH"
)

# Optional list of settings that have been removed. Leave empty if not needed.
REMOVED_SETTINGS = ( "FOO_SETTING" )


fooplugin_settings = PluginSettings("FOOPLUGIN", None, DEFAULTS, IMPORT_STRINGS)

Detailed explanation:

DEFAULTS

The DEFAULTS are, as the name says, a default array of settings. If fooplugin_setting.BLAH is not set by the user in settings.py, this default value is used.

IMPORT_STRINGS

Settings in a dotted notation are evaluated, they return not the string, but the object they point to. If it does not exist, an ImportError is raised.

REMOVED_SETTINGS

A list of settings that are forbidden to use. If accessed, an RuntimeError is raised.

This allows very flexible settings - as dependant plugins can easily import the fooplugin_settings from your conf.py.

However, the created conf.py file is not needed, so if you don’t use custom settings at all, just delete the file.

Admin site

GDAPS provides support for the Django admin site. The built-in GdapsPlugin model automatically are added to Django’s admin site, and can be administered there.

Note

As GdapsPlugin database entries must not be edited directly, they are shown read-only in the admin. Please use the ‘syncplugins’ management command to update the fields from the file system. However, you can enable/disable or hide/show plugins via the admin interface.

If you want to disable the built-in admin site for GDAPS, or provide a custom GDAPS ModelAdmin, you can do this using:

GDAPS = {
    "ADMIN": False
}

Frontend plugins

The GDAPS frontend module can be extended via plugins, each providing a pluggable frontend for your Django application. See

Signals

If you are using Django signals in your plugin, we recommend to put them into a signals submodule. Import it then from the AppConfig.ready() method.

def ready(self):
    # Import signals if necessary:
    from . import signals  # NOQA

See also

Don’t overuse the ready method. Have a look at the Django documentation of ready().