simplug 0.0.4

A simple plugin system for python with async hooks supported

simplug

A simple plugin system for python with async hooks supported

Installation

pip install -U simplug

Examples

A toy example

from simplug import Simplug

simplug = Simplug('project')

class MySpec:
    """A hook specification namespace."""

    @simplug.spec
    def myhook(self, arg1, arg2):
        """My special little hook that you can customize."""

class Plugin_1:
    """A hook implementation namespace."""

    @simplug.impl
    def myhook(self, arg1, arg2):
        print("inside Plugin_1.myhook()")
        return arg1 + arg2

class Plugin_2:
    """A 2nd hook implementation namespace."""

    @simplug.impl
    def myhook(self, arg1, arg2):
        print("inside Plugin_2.myhook()")
        return arg1 - arg2

simplug.register(Plugin_1, Plugin_2)
results = simplug.hooks.myhook(arg1=1, arg2=2)
print(results)

inside Plugin_1.myhook()
inside Plugin_2.myhook()
[3, -1]

Note that the hooks are executed in the order the plugins are registered. This is different from pluggy.

A complete example

See examples/complete/.

Running python -m examples.complete gets us:

Your food. Enjoy some egg, egg, egg, salt, pepper, egg, egg
Some condiments? We have pickled walnuts, steak sauce, mushy peas, mint sauce

After install the plugin:

> pip install --editable examples.complete.plugin
> python -m examples.complete # run again

Your food. Enjoy some egg, egg, egg, salt, pepper, egg, egg, lovely spam, wonderous spam
Some condiments? We have pickled walnuts, mushy peas, mint sauce, spam sauce
Now this is what I call a condiments tray!

Usage

Definition of hooks

Hooks are specified and implemented by decorating the functions with simplug.spec and simplug.impl respectively.

simplug is initialized by:

simplug = Simplug('project')

The 'project' is a unique name to mark the project, which makes sure Simplug('project') get the same instance each time.

Note that if simplug is initialized without project, then a name is generated automatically as such project-0, project-1, etc.

Hook specification is marked by simplug.spec:

simplug = Simplug('project')

@simplug.spec
def setup(args):
    ...

simplug.spec can take two keyword-arguments:

• required: Whether this hook is required to be implemented in plugins
• result: An enumerator to specify the way to collec the results.
  • SimplugResult.ALL: Get all the results from the hook, as a list including NONEs
  • SimplugResult.ALL_BUT_NONE: Get all the results from the hook, as a list, not including NONEs
  • SimplugResult.FIRST: Get the none-None result from the first plugin only (ordered by priority)
  • SimplugResult.LAST: Get the none-None result from the last plugin only

Hook implementation is marked by simplug.impl, which takes no additional arguments.

The name of the function has to match the name of the function by simplug.spec. And the signatures of the specification function and the implementation function have to be the same in terms of names. This means you can specify default values in the specification function, but you don't have to write the default values in the implementation function.

Note that default values in implementation functions will be ignored.

Also note if a hook specification is under a namespace, it can take self as argument. However, this argument will be ignored while the hook is being called (self will be None, and you still have to specify it in the function definition).

Loading plugins from setuptools entrypoint

You have to call simplug.load_entrypoints(group) after the hook specifications are defined to load the plugins registered by setuptools entrypoint. If group is not given, the project name will be used.

The plugin registry

The plugins are registered by simplug.register(*plugins). Each plugin of plugins can be either a python object or a str denoting a module that can be imported by importlib.import_module.

The python object must have an attribute name, __name__ or __class.__name__ for simplug to determine the name of the plugin. If the plugin name is determined from __name__ or __class__.__name__, it will be lowercased.

If a plugin is loaded from setuptools entrypoint, then the entrypoint name will be used (no matter what name is defined inside the plugin)

You can enable or disable a plugin temporarily after registration by:

simplug.disable('plugin_name')
simplug.enable('plugin_name')

You can use following methods to inspect the plugin registry:

• simplug.get_plugin: Get the plugin by name
• simplug.get_all_plugins: Get a dictionary of name-plugin mappings of all plugins
• simplug.get_all_plugin_names: Get the names of all plugins, in the order it will be executed.

Calling hooks

Hooks are call by simplug.hooks.<hook_name>(<arguments>) and results are collected based on the result argument passed in simplug.spec when defining hooks.

Async hooks

It makes no big difference to define an async hook:

@simplug.spec
async def async_hook(arg):
    ...

# to supress warnings for sync implementation
@simplug.spec(warn_sync_impl_on_async=False)
async def async_hook(arg):
    ...

One can implement this hook in either an async or a sync way. However, when implementing it in a sync way, a warning will be raised. To suppress the warning, one can pass a False value of argument warn_sync_impl_on_async to simplug.spec.

To call the async hooks (simplug.hooks.async_hook(arg)), you will just need to call it like any other async functions (using asyncio.run, for example)

API

https://pwwang.github.io/simplug/