python - 点击: how do I apply an action to all commands and subcommands but allow a command to opt-out?

Question

我有一个情况，我想为我的大多数点击命令和子命令自动运行一个通用函数 check_upgrade()，但也有少数情况我不这样做不想运行它。我想我可以有一个装饰器，可以为不应运行 check_upgrade() 的命令添加(例如 @bypass_upgrade_check)。

我希望得到类似的东西(感谢 Stephen Rauch 的最初想法):

def do_upgrade():
    print "Performing upgrade"

def bypass_upgrade_check(func):
    setattr(func, "do_upgrade_check", False)
    return func

@click.group()
@click.pass_context
def common(ctx):
    sub_cmd = ctx.command.commands[ctx.invoked_subcommand]
    if getattr(sub_cmd, "do_upgrade_check", True):
        do_upgrade()

@bypass_upgrade_check
@common.command()
def top_cmd1():
    # don't run do_upgrade() on top level command
    pass

@common.command()
def top_cmd2():
    # DO run do_upgrade() on top level command
    pass

@common.group()
def sub_cmd_group():
    pass

@bypass_upgrade_check
@sub_cmd.command()
def sub_cmd1():
    # don't run do_upgrade() on second-level command
    pass

@sub.command()
def sub_cmd2():
    # DO run do_upgrade() on second-level command
    pass

不幸的是，这仅适用于顶级命令，因为 ctx.invoked_subcommand 引用 sub_cmd_group 而不是 sub_cmd1 或 sub_cmd2。

有没有办法递归搜索子命令，或者使用自定义组能够通过顶级命令和子命令来实现此功能？

Answer 1

解决此问题的一种方法是构建一个与自定义 click.Group 类配对的自定义装饰器:

自定义装饰器生成器:

def make_exclude_hook_group(callback):
    """ for any command that is not decorated, call the callback """

    hook_attr_name = 'hook_' + callback.__name__

    class HookGroup(click.Group):
        """ group to hook context invoke to see if the callback is needed"""

        def invoke(self, ctx):
            """ group invoke which hooks context invoke """
            invoke = ctx.invoke

            def ctx_invoke(*args, **kwargs):
                """ monkey patched context invoke """
                sub_cmd = ctx.command.commands[ctx.invoked_subcommand]
                if not isinstance(sub_cmd, click.Group) and \
                        getattr(sub_cmd, hook_attr_name, True):
                    # invoke the callback
                    callback()
                return invoke(*args, **kwargs)

            ctx.invoke = ctx_invoke

            return super(HookGroup, self).invoke(ctx)

        def group(self, *args, **kwargs):
            """ new group decorator to make sure sub groups are also hooked """
            if 'cls' not in kwargs:
                kwargs['cls'] = type(self)
            return super(HookGroup, self).group(*args, **kwargs)

    def decorator(func=None):
        if func is None:
            # if called other than as decorator, return group class
            return HookGroup

        setattr(func, hook_attr_name, False)

    return decorator

使用装饰器构建器:

要使用装饰器，我们首先需要构建装饰器，例如:

bypass_upgrade_check = make_exclude_hook_group(do_upgrade)

然后我们需要将其用作click.group()的自定义类，例如:

@click.group(cls=bypass_upgrade_check())
...

最后，我们可以将任何命令或子命令装饰到不需要使用回调的组中，例如:

@bypass_upgrade_check
@my_group.command()
def my_click_command_without_upgrade():
     ...

这是如何工作的？

这是有效的，因为 click 是一个设计良好的 OO 框架。 @click.group() 装饰器通常会实例化 click.Group 对象，但允许使用 cls 参数覆盖此行为。因此，在我们自己的类中继承 click.Group 并覆盖所需的方法是一件相对容易的事情。

在这种情况下，我们构建一个装饰器，在不需要调用回调的任何单击函数上设置属性。然后在我们的自定义组中，我们猴子修补上下文的 click.Context.invoke() ，如果即将执行的命令尚未修饰，我们将调用回调。

测试代码:

import click

def do_upgrade():
    print("Performing upgrade")

bypass_upgrade_check = make_exclude_hook_group(do_upgrade)

@click.group(cls=bypass_upgrade_check())
@click.pass_context
def cli(ctx):
    pass

@bypass_upgrade_check
@cli.command()
def top_cmd1():
    click.echo('cmd1')

@cli.command()
def top_cmd2():
    click.echo('cmd2')

@cli.group()
def sub_cmd_group():
    click.echo('sub_cmd_group')

@bypass_upgrade_check
@sub_cmd_group.command()
def sub_cmd1():
    click.echo('sub_cmd1')

@sub_cmd_group.command()
def sub_cmd2():
    click.echo('sub_cmd2')

if __name__ == "__main__":
    commands = (
        'top_cmd1',
        'top_cmd2',
        'sub_cmd_group sub_cmd1',
        'sub_cmd_group sub_cmd2',
        '--help',
    )

    import sys, time

    time.sleep(1)
    print('Click Version: {}'.format(click.__version__))
    print('Python Version: {}'.format(sys.version))
    for cmd in commands:
        try:
            time.sleep(0.1)
            print('-----------')
            print('> ' + cmd)
            time.sleep(0.1)
            cli(cmd.split())

        except BaseException as exc:
            if str(exc) != '0' and \
                    not isinstance(exc, (click.ClickException, SystemExit)):
                raise

结果:

Click Version: 6.7
Python Version: 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]
-----------
> top_cmd1
cmd1
-----------
> top_cmd2
Performing upgrade
cmd2
-----------
> sub_cmd_group sub_cmd1
sub_cmd_group
sub_cmd1
-----------
> sub_cmd_group sub_cmd2
Performing upgrade
sub_cmd_group
sub_cmd2
-----------
> --help
Usage: test.py [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  sub_cmd_group
  top_cmd1
  top_cmd2