python中的互斥命令单击

Question

我有一个带有三个命令的click 应用程序：

import click

@click.group(chain=True)
def cli():
    print("MAIN")

@cli.command()
def initialize():
    print("INITIALIZING")
    
@cli.command()
def update():
    print("UPDATING")

@cli.command()
def process():
    print("PROCESSING")

这样定义，所有的命令都可以链接起来。

但是，我怎样才能使initialize 和update 互斥？ IE：应该是：

合法运行：

initialize -> process

和

update -> process

不合法运行：

initialize -> update -> process

Answer 1

您可以通过创建自定义click.Group 类将可链接命令标记为互斥。

自定义类

class MutuallyExclusiveCommandGroup(click.Group):
    def __init__(self, *args, **kwargs):
        kwargs['chain'] = True
        self.mutually_exclusive = []
        super().__init__(*args, **kwargs)

    def command(self, *args, mutually_exclusive=False, **kwargs):
        """Track the commands marked as mutually exclusive"""
        super_decorator = super().command(*args, **kwargs)
        def decorator(f):
            command = super_decorator(f)
            if mutually_exclusive:
                self.mutually_exclusive.append(command)
            return command
        return decorator

    def resolve_command(self, ctx, args):
        """Hook the command resolving and verify mutual exclusivity"""
        cmd_name, cmd, args = super().resolve_command(ctx, args)

        # find the commands which are going to be run
        if not hasattr(ctx, 'resolved_commands'):
            ctx.resolved_commands = set()
        ctx.resolved_commands.add(cmd_name)

        # if args is empty we have have found all of the commands to be run
        if not args:
            mutually_exclusive = ctx.resolved_commands & set(
                cmd.name for cmd in self.mutually_exclusive)
            if len(mutually_exclusive) > 1:
                raise click.UsageError(
                    "Illegal usage: commands: `{}` are mutually exclusive".format(
                        ', '.join(mutually_exclusive)))

        return cmd_name, cmd, args

    def get_help(self, ctx):
        """Extend the short help for the mutually exclusive commands"""
        for cmd in self.mutually_exclusive:
            mutually_exclusive = set(self.mutually_exclusive)
            if not cmd.short_help:
                cmd.short_help = 'mutually exclusive with: {}'.format(', '.join(
                    c.name for c in mutually_exclusive if c.name != cmd.name))
        return super().get_help(ctx)

使用自定义类：

要使用自定义类，请将其作为 cls 参数传递给 click.group 装饰器，例如：

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

然后使用mutually_exclusive 装饰器的mutually_exclusive 参数来标记命令 作为互斥组的一部分。

@cli.command(mutually_exclusive=True)
def update():
    ...

这是如何工作的？

这是可行的，因为 click 是一个设计良好的 OO 框架。 @click.group() 装饰器 通常实例化 click.Group 对象，但允许使用 cls 覆盖此行为 范围。所以在我们自己的类及以上继承click.Group是一件相对容易的事情 骑所需的方法。

在这种情况下，我们覆盖了三个方法：command(), resolve_command() & get_help()。被覆盖的 command() 方法允许我们跟踪哪些命令标记有mutually_exclusive 标志。这 overridden resolve_command() 方法用于观察命令解析过程，注意哪个 命令将被运行。如果要运行互斥命令，则会引发错误。这 重写的get_help 方法设置short_help 属性以显示哪些命令是互斥的。

测试代码：

import click

@click.group(chain=True, cls=MutuallyExclusiveCommandGroup)
@click.pass_context
def cli(ctx):
    print("MAIN")

@cli.command()
def initialize():
    print("INITIALIZING")

@cli.command(mutually_exclusive=True)
def update():
    print("UPDATING")

@cli.command(mutually_exclusive=True)
def process():
    print("PROCESSING")


if __name__ == "__main__":
    commands = (
        '',
        'initialize',
        'update',
        'process',
        'initialize process',
        'update process',
        'initialize update process',
        '--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

测试结果：

Click Version: 7.1.2
Python Version: 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:57:54) [MSC v.1924 64 bit (AMD64)]
-----------
>
Usage: test_code.py [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

Options:
  --help  Show this message and exit.

Commands:
  initialize
  process     mutually exclusive with: update
  update      mutually exclusive with: process
-----------
> initialize
MAIN
INITIALIZING
-----------
> update
MAIN
UPDATING
-----------
> process
MAIN
PROCESSING
-----------
> initialize process
MAIN
INITIALIZING
PROCESSING
-----------
> update process
MAIN
Error: Illegal usage: commands: `update, process` are mutually exclusive
-----------
> initialize update process
MAIN
Error: Illegal usage: commands: `update, process` are mutually exclusive
-----------
> --help
Usage: test_code.py [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

Options:
  --help  Show this message and exit.

Commands:
  initialize
  process     mutually exclusive with: update
  update      mutually exclusive with: process.