Usage

Creating plugins

Create plugins using a Django management command:

./manage.py startplugin fooplugin

This command asks a few questions, creates a basic Django app in the FRONTEND_DIR chosen before, and provides useful defaults as well as a setup.py file.

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

You now have two choices for this plugin: * add it statically to INSTALLED_APPS: see Static plugins. * make use of the dynamic loading feature: see Dynamic plugins.

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, bug your GDAPS enhanced Django application can make use of it’s enhanced GDAPS features.

Dynamic plugins

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

pipenv 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.

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. Interfaces must not be defined in that module, but it is a recommended coding style for GDAPS plugins:

from gdaps import Interface

class IFooInterface(Interface):
    """Documentation of the interface"""

    class Meta:
        service = True

    def do_something(self):
        pass

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

service

If service=True (which is the default), then all implementations are instantiated instantly at definition time, having a full class instance availably at any time. You then can iterate over ExtensionPoints and use the instances directly.

If you use service=False, ExtensionPoint iterations will return classes, not instances. This sometimes may be the desired functionality.

ExtensionPoints

An ExtensionPoint (EP) is a plugin hook that refers to an Interface. An EP can be defined anywhere in code. You can then get all the plugins that implement that interface by just iterating over that ExtensionPoint:

```python from gdaps import ExtensionPoint from myproject.plugins.fooplugin.api.interfaces import IFooInterface

class MyPlugin: ep = ExtensionPoint(IFooInterface)

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

```

Keep in mind that iterating over an ExtensionPoint does not return instances of plugins. It just returns the class that was decorated with @implements. This might be improved in the future (auto-instantiated plugins).

Implementations

You can then easily implement this interface in any other file (in this plugin or in another plugin) using the @implements decorator syntax:

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

@implements(IFooInterface)
class OtherPluginClass:

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

I didn’t want to force implementations to inherit a Plugin base class, like some other plugin systems do. This would mean that implementations won’t be as flexible as I wanted them. When just using a decorator, you can easily use ANY, even your already existing, class and just ducktype-implement the methods the Interface demands. If you forget to implement a method, GDAPS will complain instantly.

If you need a more “Plugin”-like class, just create a class that implements the gdaps.IPlugin interface, or use the included gdaps.Plugin class as parent for your convenience.

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.

Frontend support

GDAPS supports Javascript frontends for building e.g. SPA applications. ATM only Vue.js ist supported, but PRs are welcome to add more (Angular, React?).

If you add gdaps.frontend to INSTALLED_APPS, there is a new management command available: manage.py initfrontend. It has one mandatory parameter, the frontend engine:

:: code-block:: bash

./manage.py initfrontend vue

This creates a /frontend/ directory in the project root. Change into that directory and run yarn install once to install all the dependencies of Vue.js needed.

It is recommended to install vue globally, you can do that with yarn global add @vue/cli @vue/cli-service-global.

Now you can start yarn serve in the frontend directory. This starts a development web server that bundles the frontend app using webpack automatically. You then need to start Django using ./manage.py runserver to enable the Django backend. GDAPS manages all the needed background tasks to transparently enable hot-reloading when you change anything in the frontend source code now.