Announcing Poetry 1.2.0a1

The Poetry team is pleased to announce the immediate availability of Poetry 1.2.0a1.

This release is the first testing release of the upcoming 1.2.0 version.

It adds – among other things – support for plugins and for PEP 610.

For a complete list of changes, you can refer to the change log.

Deprecation of the get-poetry.py script #

The usage of the get-poetry.py script is now deprecated and is replaced by the install-poetry.py script:

curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/install-poetry.py | python -

The reasons for this change are the following:

• It no longer relies on the prebuilt release packages of Poetry (see https://github.com/python-poetry/poetry/releases/tag/1.1.5 for an example) which had the issues of having frozen dependencies which made upgrading dependencies much harder without releasing a new bug fix release of Poetry. This will eventually make our release process easier.
• It relies on standards for the install locations of both Poetry and the poetry script.
• It supports installing from a git repository or a file/directory.
• It no longer tries to modify the PATH but instead will simply provide guidance on how to do it if necessary.
• It will use the correct Python interpreter, i.e. the one used to invoke the script, when calling the poetry script.

It also ensures that the plugin system, detailed below, works properly.

Poetry users are encouraged to use this new script since the newest releases (including this one) won’t be available via the old installer.

New plugin system #

Poetry now supports a plugin system to alter or expand Poetry’s functionality.

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 = "~2.7 || ^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.

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):
        version = self.get_custom_version()
        io.write_line(f"Setting package version to <b>{version}</b>")
        poetry.package.set_version(version)

    def get_custom_version(self) -> str:
        ...

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 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 an 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

The plugin add command #

This is the easiest way and should account for all the ways Poetry can be installed.

poetry plugin add poetry-plugin

The plugin 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 plugin 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 plugin remove command.

poetry plugin remove poetry-plugin

You can also list all currently installed plugins by running:

poetry plugin show

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 #

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

pip install --user poetry-plugin

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

pip uninstall poetry-plugin

PEP 610 support #

Poetry now supports PEP 610 both in writing and in reading.

This should address issues and performances in determining the origin of the installed packages.