Python Dependency Manager Companion

--- title: "Plugins" draft: false type: docs layout: single menu: docs: weight: 80 --- # 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]({{< relref "pyproject#plugins" >}}) in the `pyproject.toml` file. ```toml [project] name = "my-poetry-plugin" version = "1.0.0" # ... requires-python = ">=3.7" dependencies = [ "poetry (>=1.2,<2.0)", ] [project.entry-points."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: ```python 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`. ```python 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) ``` {{% note %}} It's possible to do the following to register the command: ```python application.add(MyCommand()) ``` However, it is **strongly** recommended to register a new factory in the command loader to defer the loading of the command when it's actually called. This will help keep the performances of Poetry good. {{% /note %}} The plugin also must be declared in the `pyproject.toml` file of the plugin package as a `poetry.application.plugin` plugin: ```toml [tool.poetry.plugins."poetry.application.plugin"] foo-command = "poetry_demo_plugin.plugin:MyApplicationPlugin" ``` {{% warning %}} A plugin **must not** remove or modify in any way the core commands of Poetry. {{% /warning %}} ### Event handler Plugins can also listen to specific events and act on them if necessary. These events are fired by [Cleo](https://github.com/python-poetry/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. ```python 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. ```shell pipx inject poetry poetry-plugin ``` If you want to uninstall a plugin, you can run: ```shell pipx uninject poetry poetry-plugin # For pipx versions >= 1.2.0 pipx runpip poetry uninstall poetry-plugin # For pipx versions < 1.2.0 ``` ### 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](/docs/) can be referenced if you are not sure where Poetry has been installed. To add a plugin, you can use `pip install`: ```shell $POETRY_HOME/bin/pip install --user poetry-plugin ``` If you want to uninstall a plugin, you can run: ```shell $POETRY_HOME/bin/pip uninstall poetry-plugin ``` ### The `self add` command {{% warning %}} Especially on Windows, `self add` and `self remove` may be problematic so that other methods should be preferred. {{% /warning %}} ```bash 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]({{< relref "cli#add" >}}). If you no longer need a plugin and want to uninstall it, you can use the `self remove` command. ```shell poetry self remove poetry-plugin ``` You can also list all currently installed plugins by running: ```shell poetry self show plugins ``` ### Project plugins You can also specify that a plugin is required for your project in the `tool.poetry.requires-plugins` section of the pyproject.toml file: ```toml [tool.poetry.requires-plugins] my-application-plugin = ">1.0" ``` If the plugin is not installed in Poetry's own environment when running `poetry install`, it will be installed only for the current project under `.poetry/plugins` in the project's directory. The syntax to specify `plugins` is the same as for [dependencies]({{< relref "managing-dependencies" >}}). {{% warning %}} You can even overwrite a plugin in Poetry's own environment with another version. However, if a plugin's dependencies are not compatible with packages in Poetry's own environment, installation will fail. {{% /warning %}} ## 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 main 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.