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|
# This file is part of 'click-plugins': https://github.com/click-contrib/click-plugins
#
# New BSD License
#
# Copyright (c) 2015-2025, Kevin D. Wurster, Sean C. Gillies
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# * Neither click-plugins nor the names of its contributors may not be used to
# endorse or promote products derived from this software without specific prior
# written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""Support CLI plugins with click and entry points.
See :func:`with_plugins`.
"""
import importlib.metadata
import os
import sys
import traceback
import click
__version__ = '2.0'
def with_plugins(entry_points):
"""Decorator for loading and attaching plugins to a ``click.Group()``.
Plugins are loaded from an ``importlib.metadata.EntryPoint()``. Each entry
point must point to a ``click.Command()``. An entry point that fails to
load will be wrapped in a ``BrokenCommand()`` to allow the CLI user to
discover and potentially debug the problem.
>>> from importlib.metadata import entry_points
>>>
>>> import click
>>> from click_plugins import with_plugins
>>>
>>> @with_plugins('group_name')
>>> @click.group()
>>> def group():
... '''Group'''
>>>
>>> @with_plugins(entry_points('group_name'))
>>> @click.group()
>>> def group():
... '''Group'''
>>>
>>> @with_plugins(importlib.metadata.EntryPoint(...))
>>> @click.group()
>>> def group():
... '''Group'''
>>>
>>> @with_plugins("group1")
>>> @with_plugins("group2")
>>> def group():
... '''Group'''
:param str or EntryPoint or sequence[EntryPoint] entry_points:
Entry point group name, a single ``importlib.metadata.EntryPoint()``,
or a sequence of ``EntryPoint()``s.
:rtype function:
"""
# Note that the explicit full path reference to:
#
# importlib.metadata.entry_points()
#
# in this function allows the call to be mocked in the tests. Replacing
# with:
#
# from importlib.metadata import entry_points
#
# breaks this ability.
def decorator(group):
if not isinstance(group, click.Group):
raise TypeError(
f"plugins can only be attached to an instance of"
f" 'click.Group()' not: {repr(group)}")
# Load 'EntryPoint()' objects.
if isinstance(entry_points, str):
# Older versions of Python do not support filtering.
if sys.version_info >= (3, 10):
all_entry_points = importlib.metadata.entry_points(
group=entry_points)
else:
all_entry_points = importlib.metadata.entry_points()
all_entry_points = all_entry_points[entry_points]
# A single 'importlib.metadata.EntryPoint()'
elif isinstance(entry_points, importlib.metadata.EntryPoint):
all_entry_points = [entry_points]
# Sequence of 'EntryPoints()'.
else:
all_entry_points = entry_points
for ep in all_entry_points:
try:
group.add_command(ep.load())
# Catch all exceptions (technically not 'BaseException') and
# instead register a special 'BrokenCommand()'. Otherwise, a single
# plugin that fails to load and/or register will make the CLI
# inoperable. 'BrokenCommand()' explains the situation to users.
except Exception as e:
group.add_command(BrokenCommand(ep, e))
return group
return decorator
class BrokenCommand(click.Command):
"""Represents a plugin ``click.Command()`` that failed to load.
Can be executed just like a ``click.Command()``, but prints information
for debugging and exits with an error code.
"""
def __init__(self, entry_point, exception):
"""
:param importlib.metadata.EntryPoint entry_point:
Entry point that failed to load.
:param Exception exception:
Raised when attempting to load the entry point associated with
this instance.
"""
super().__init__(entry_point.name)
# There are several ways to get a traceback from an exception, but
# 'TracebackException()' seems to be the most portable across actively
# supported versions of Python.
tbe = traceback.TracebackException.from_exception(exception)
# A message for '$ cli command --help'. Contains full traceback and a
# helpful note. The intention is to nudge users to figure out which
# project should get a bug report since users are likely to report the
# issue to the developers of the CLI utility they are directly
# interacting with. These are not necessarily the right developers.
self.help = (
"{ls}ERROR: entry point '{module}:{name}' could not be loaded."
" Contact its author for help.{ls}{ls}{tb}").format(
module=_module(entry_point),
name=entry_point.name,
ls=os.linesep,
tb=''.join(tbe.format())
)
# Replace the broken command's summary with a warning about how it
# was not loaded successfully. The idea is that '$ cli --help' should
# include a clear indicator that a subcommand is not functional, and
# a little hint for what to do about it. U+2020 is a "dagger", whose
# modern use typically indicates a footnote.
self.short_help = (
f"\u2020 Warning: could not load plugin. Invoke command with"
f" '--help' for traceback."
)
def invoke(self, ctx):
"""Print traceback and debugging message.
:param click.Context ctx:
Active context.
"""
click.echo(self.help, color=ctx.color, err=True)
ctx.exit(1)
def parse_args(self, ctx, args):
"""Pass arguments along without parsing.
:param click.Context ctx:
Active context.
:param list args:
List of command line arguments.
"""
# Do not attempt to parse these arguments. We do not know why the
# entry point failed to load, but it is reasonable to assume that
# argument parsing will not work. Ultimately the goal is to get the
# 'Command.invoke()' method (overloaded in this class) to execute
# and provide the user with a bit of debugging information.
return args
def _module(ep):
"""Module name for a given entry point.
Parameters
----------
ep : importlib.metadata.EntryPoint
Determine parent module for this entry point.
Returns
-------
str
"""
if sys.version_info >= (3, 10):
module = ep.module
else:
# From 'importlib.metadata.EntryPoint.module'.
match = ep.pattern.match(ep.value)
module = match.group('module')
return module
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