Plugins

Plugins #

Poetry supports using and building plugins if you wish to alter or expand Poetry’s functionality with your own.

For example if your environment poses special requirements on the behaviour of Poetry which do not apply to the majority of its users or if you wish to accomplish something with Poetry in a way that is not desired by most users.

In these cases you could consider creating a plugin to handle your specific logic.

Creating a plugin #

A plugin is a regular Python package which ships its code as part of the package and may also depend on further packages.

Plugin package #

The plugin package must depend on Poetry and declare a proper plugin in the pyproject.toml file.

[tool.poetry]
name = "my-poetry-plugin"
version = "1.0.0"

# ...
[tool.poetry.dependencies]
python = "^3.7"
poetry = "^1.2"

[tool.poetry.plugins."poetry.plugin"]
demo = "poetry_demo_plugin.plugin:MyPlugin"

Generic plugins #

Every plugin has to supply a class which implements the poetry.plugins.Plugin interface.

The activate() method of the plugin is called after the plugin is loaded and receives an instance of Poetry as well as an instance of cleo.io.io.IO.

Using these two objects all configuration can be read and all public internal objects and state can be manipulated as desired.

Example:

from cleo.io.io import IO

from poetry.plugins.plugin import Plugin
from poetry.poetry import Poetry


class MyPlugin(Plugin):

    def activate(self, poetry: Poetry, io: IO):
        io.write_line("Setting readme")
        poetry.package.readme = "README.md"
        ...

Application plugins #

If you want to add commands or options to the poetry script you need to create an application plugin which implements the poetry.plugins.ApplicationPlugin interface.

The activate() method of the application plugin is called after the plugin is loaded and receives an instance of poetry.console.Application.

from cleo.commands.command import Command
from poetry.plugins.application_plugin import ApplicationPlugin


class CustomCommand(Command):

    name = "my-command"

    def handle(self) -> int:
        self.line("My command")

        return 0


def factory():
    return CustomCommand()


class MyApplicationPlugin(ApplicationPlugin):
    def activate(self, application):
        application.command_loader.register_factory("my-command", factory)

application.add(MyCommand())

The plugin also must be declared in the pyproject.toml file of the plugin package as a poetry.application.plugin plugin:

[tool.poetry.plugins."poetry.application.plugin"]
foo-command = "poetry_demo_plugin.plugin:MyApplicationPlugin"

Event handler #

Plugins can also listen to specific events and act on them if necessary.

These events are fired by Cleo and are accessible from the cleo.events.console_events module.

• COMMAND: this event allows attaching listeners before any command is executed.
• SIGNAL: this event allows some actions to be performed after the command execution is interrupted.
• TERMINATE: this event allows listeners to be attached after the command.
• ERROR: this event occurs when an uncaught exception is raised.

Let’s see how to implement an application event handler. For this example we will see how to load environment variables from a .env file before executing a command.

from cleo.events.console_events import COMMAND
from cleo.events.console_command_event import ConsoleCommandEvent
from cleo.events.event_dispatcher import EventDispatcher
from dotenv import load_dotenv
from poetry.console.application import Application
from poetry.console.commands.env_command import EnvCommand
from poetry.plugins.application_plugin import ApplicationPlugin


class MyApplicationPlugin(ApplicationPlugin):
    def activate(self, application: Application):
        application.event_dispatcher.add_listener(
            COMMAND, self.load_dotenv
        )

    def load_dotenv(
        self,
        event: ConsoleCommandEvent,
        event_name: str,
        dispatcher: EventDispatcher
    ) -> None:
        command = event.command
        if not isinstance(command, EnvCommand):
            return

        io = event.io

        if io.is_debug():
            io.write_line(
                "<debug>Loading environment variables.</debug>"
            )

        load_dotenv()

Using plugins #

Installed plugin packages are automatically loaded when Poetry starts up.

You have multiple ways to install plugins for Poetry

With pipx inject #

If you used pipx to install Poetry you can add the plugin packages via the pipx inject command.

pipx inject poetry poetry-plugin

If you want to uninstall a plugin, you can run:

pipx runpip poetry uninstall poetry-plugin

With pip #

The pip binary in Poetry’s virtual environment can also be used to install and remove plugins. The environment variable $POETRY_HOME here is used to represent the path to the virtual environment. The installation instructions can be referenced if you are not sure where Poetry has been installed.

To add a plugin, you can use pip install:

$POETRY_HOME/bin/pip install --user poetry-plugin

If you want to uninstall a plugin, you can run:

$POETRY_HOME/bin/pip uninstall poetry-plugin

The self add command #

poetry self add poetry-plugin

The self add command will ensure that the plugin is compatible with the current version of Poetry and install the needed packages for the plugin to work.

The package specification formats supported by the self add command are the same as the ones supported by the add command.

If you no longer need a plugin and want to uninstall it, you can use the self remove command.

poetry self remove poetry-plugin

You can also list all currently installed plugins by running:

poetry self show plugins

Maintaining a plugin #

When writing a plugin, you will probably access internals of Poetry, since there is no stable public API. Although we try our best to deprecate methods first, before removing them, sometimes the signature of an internal method has to be changed.

As the author of a plugin, you are probably testing your plugin against the latest release of Poetry. Additionally, you should consider testing against the latest release branch and the master branch of Poetry and schedule a CI job that runs regularly even if you did not make any changes to your plugin. This way, you will notice internal changes that break your plugin immediately and can prepare for the next Poetry release.