Discord.py 上作为装饰器的异步函数

Question

我有一个 Discord.py 命令，我想制作一个自定义权限处理程序。

我的命令：

@commands.command()
@custom_permission("administrator")
async def example(self, ctx, args):
    ...

在这种情况下，@custom_permission() 是权限处理程序，现在我如何让它适用于异步定义中的装饰器？

装饰函数：

async def custom_permission(permission):
    
    async def predicate(ctx, permission):
        if ctx.author.id in config.owners:
            return True

        elif permission == "administrator":
            if ctx.author.guild_permissions.administrator:
                return True

            else:
                embed = discord.Embed(timestamp=ctx.message.created_at, description=f"You do not meet the required guild permissions the command \"`{ctx.command.name}`\" requires to be executed.\n\nYou need `{permission.upper()}` Permission in this Guild to be able to execute/run/use this command.", color=242424)
                embed.set_author(name="Insufficient Permissions", icon_url=config.forbidden_img)
                embed.set_footer(text="Numix", icon_url=config.logo)
                await ctx.send(embed=embed)

        elif permission == "manage_messages":
            if ctx.author.guild_permissions.manage_messages:
                return True

            else:
                embed = discord.Embed(timestamp=ctx.message.created_at, description=f"You do not meet the required guild permissions the command \"`{ctx.command.name}`\" requires to be executed.\n\nYou need `{permission.upper()}` Permission in this Guild to be able to execute/run/use this command.", color=242424)
                embed.set_author(name="Insufficient Permissions", icon_url=config.forbidden_img)
                embed.set_footer(text="Numix", icon_url=config.logo)
                await ctx.send(embed=embed)

        elif permission == "kick":
            if ctx.author.guild_permissions.kick:
                return True

            else:
                embed = discord.Embed(timestamp=ctx.message.created_at, description=f"You do not meet the required guild permissions the command \"`{ctx.command.name}`\" requires to be executed.\n\nYou need `{permission.upper()}` Permission in this Guild to be able to execute/run/use this command.", color=242424)
                embed.set_author(name="Insufficient Permissions", icon_url=config.forbidden_img)
                embed.set_footer(text="Numix", icon_url=config.logo)
                await ctx.send(embed=embed)

        elif permission == "ban":
            if ctx.author.guild_permissions.ban:
                return True
                
            else:
                embed = discord.Embed(timestamp=ctx.message.created_at, description=f"You do not meet the required guild permissions the command \"`{ctx.command.name}`\" requires to be executed.\n\nYou need `{permission.upper()}` Permission in this Guild to be able to execute/run/use this command.", color=242424)
                embed.set_author(name="Insufficient Permissions", icon_url=config.forbidden_img)
                embed.set_footer(text="Numix", icon_url=config.logo)
                await ctx.send(embed=embed)

        elif permission == "manage_guild":
            if ctx.author.guild_permissions.manage_guild:
                return True

            else:
                embed = discord.Embed(timestamp=ctx.message.created_at, description=f"You do not meet the required guild permissions the command \"`{ctx.command.name}`\" requires to be executed.\n\nYou need `{permission.upper()}` Permission in this Guild to be able to execute/run/use this command.", color=242424)
                embed.set_author(name="Insufficient Permissions", icon_url=config.forbidden_img)
                embed.set_footer(text="Numix", icon_url=config.logo)
                await ctx.send(embed=embed)
        

    return commands.check(predicate(ctx, permission))

现在，我该怎么做呢？我无法将其更改为普通功能，因为如果我那样做，则在满足权限要求时我无法发送嵌入消息。

Answer 1

你不需要让最外层的函数异步，但是 predicate 函数可以是协程

def custom_permission(permission):
    async def predicate(ctx):
        ...
    return commands.check(predicate)

记住predicate协程只能接受一个参数，ctx（参数在commands.check方法内部传递，你不自己传递）如果您想访问其他参数，请使用 ctx.args.

Answer 2

装饰器语法：

@decorator
def function():
    ...

只是语法糖：

def function():
    ...
function = decorator(function)

异步函数是 returns 协程的函数。


In [1]: async def foo():
   ...:     return 42
   ...: 

In [2]: await foo()
Out[2]: 42

In [3]: foo()
Out[3]: <coroutine object foo at 0x7f7ca626da40>

所以当你这样做时

@an_async_function("argument")
async def foo():
    ...

an_async_function("argument") 将是您尝试调用的协程对象。

commands.check 需要一个异步函数，而您正在传递对该函数的调用。

您可以做的是：

a) 使用 functools.partial 将 predicate 函数部分应用到 permissions 参数：

async def _check_permission(ctx, permission):
    ...

def custom_permission(permission):

    return commands.check(partial(_check_permission, permission=permission))

b) 只需在 predicate.

中使用您在装饰器中传递的 permission

def custom_permission(permission):
    
    async def predicate(ctx):
        ...  # use `permission` here

    return commands.check(predicate)

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