如何为 rust 中的 clap 结构创建自定义派生宏？

Question

我正在尝试在 rust 中创建某种简单的 CLI 计费应用程序以供练习。 它是一种数据库应用程序。 我有许多操作，我需要用户能够根据将对其进行操作的列的值进行过滤。

对于下面的示例，有删除和显示命令：

#[derive(Debug, Args)]
struct DeleteCommand {
    /// The ID of the bill
    #[clap(short, long, value_parser)]
    id: Option<String>,
    /// The name of the bill
    #[clap(short, long, value_parser)]
    name: Option<String>,
    /// The value of the bill
    #[clap(short, long, value_parser)]
    value: Option<String>,
    /// The amount of the billB
    #[clap(short, long, value_parser)]
    amount: Option<String>,
    /// Datetime
    #[clap(short, long, value_parser)]
    datetime: Option<String>,
    /// Currency
    #[clap(short, long, value_parser)]
    currency: Option<String>,
    /// Recipient
    #[clap(short, long, value_parser)]
    recipient: Option<String>,
    /// Situation
    #[clap(short, long, value_parser)]
    situation: Option<String>,
    /// Hard
    #[clap(short = 'H', long)]
    hard: bool,
}

#[derive(Debug, Args)]
struct ShowCommand {
    #[clap(subcommand)]
    subcommand: ShowSubcommand,
    /// The ID of the bill
    #[clap(short, long, value_parser)]
    id: Option<String>,
    /// The name of the bill
    #[clap(short, long, value_parser)]
    name: Option<String>,
    /// The value of the bill
    #[clap(short, long, value_parser)]
    value: Option<String>,
    /// The amount of the bill
    #[clap(short, long, value_parser)]
    amount: Option<String>,
    /// Datetime
    #[clap(short, long, value_parser)]
    datetime: Option<String>,
    /// Currency
    #[clap(short, long, value_parser)]
    currency: Option<String>,
    /// Datetime
    #[clap(short, long, value_parser)]
    recipient: Option<String>,
    /// Datetime
    #[clap(short, long, value_parser)]
    situation: Option<String>,
    /// Head
    #[clap(long, value_parser)]
    head: Option<u32>,
    /// Tail
    #[clap(long, value_parser)]
    tail: Option<u32>,
    /// Order by
    #[clap(short, long, value_parser)]
    orderby: Option<String>,
}

如您所见，两个结构之间有许多公共字段，因为两者都需要过滤数据库中的项目。 我只想创建一个派生自定义宏，让我可以简单地在结构中重复这些行，而无需一次又一次地编写它：

    /// The ID of the bill
    #[clap(short, long, value_parser)]
    id: Option<String>,
    /// The name of the bill
    #[clap(short, long, value_parser)]
    name: Option<String>,
    /// The value of the bill
    #[clap(short, long, value_parser)]
    value: Option<String>,
    /// The amount of the bill
    #[clap(short, long, value_parser)]
    amount: Option<String>,
    /// Datetime
    #[clap(short, long, value_parser)]
    datetime: Option<String>,
    /// Currency
    #[clap(short, long, value_parser)]
    currency: Option<String>,
    /// Recipient
    #[clap(short, long, value_parser)]
    recipient: Option<String>,
    /// Situation
    #[clap(short, long, value_parser)]
    situation: Option<String>,

我还需要重复 /// 行，因为它将成为 CLI 中每个参数的描述。

最小可重现示例：

这就是我所拥有的

use clap::{Parser, Subcommand, Args};

#[derive(Debug, Parser)]
pub struct UserInput {
    #[clap(subcommand)]
    command: Command,
}

#[derive(Debug, Subcommand)]
enum Command {
    /// A command description
    A(CommandA),
    /// B command description
    B(CommandB),
}

#[derive(Debug, Args)]
struct CommandA {
    /// The value of column x to be filtered in the database
    #[clap(short, long, value_parser)]
    x_value: Option<String>,
    /// The value of column y to be filtered in the database
    #[clap(short, long, value_parser)]
    y_value: Option<String>,
    /// Some particular parameter of this command
    #[clap(short, long, value_parser)]
    particular: Option<String>,
}

#[derive(Debug, Args)]
struct CommandB {
    /// The value of x to be filtered in the database
    #[clap(short, long, value_parser)]
    x_value: Option<String>,
    /// The value of y to be filtered in the database
    #[clap(short, long, value_parser)]
    y_value: Option<String>,
    /// Some particular parameter of this command
    #[clap(short, long, value_parser)]
    particular: Option<String>,
}

fn main() {
    let user_input: UserInput = UserInput::parse();
    print!("{:#?}", user_input)
}

这就是我要的：

use clap::{Parser, Subcommand, Args};

#[derive(Debug, Parser)]
pub struct UserInput {
    #[clap(subcommand)]
    command: Command,
}

#[derive(Debug, Subcommand)]
enum Command {
    /// A command description
    A(CommandA),
    /// B command description
    B(CommandB),
}

#[derive(Debug, Args, Filter)]
struct CommandA {
    /// Some particular parameter command A
    #[clap(short, long, value_parser)]
    particular: Option<String>,
}

#[derive(Debug, Args, Filter)]
struct CommandB {
    /// Some particular parameter command B
    #[clap(short, long, value_parser)]
    particular: Option<String>,
}

fn main() {
    let user_input: UserInput = UserInput::parse();
    print!("{:#?}", user_input)
}

等待行为：

[user@host appname]$ appname a --help
p1-a 
A command description

USAGE:
    p1 a [OPTIONS]

OPTIONS:
    -x, --x-value <X_VALUE>          The value of column X to be filtered in the database
    -y, --y-value <Y_VALUE>          The value of column Y to be filtered in the database
    -h, --help                       Print help information
    -p, --particular <PARTICULAR>    Some particular parameter of command A

编辑：我正在使用 clap 3.2.22，但我会尝试将我的代码移动到最新版本。

Answer 1

您可以像这样使用组合和#[clap(flatten)]来实现您想要的效果：

use clap::{Args, Parser, Subcommand};
#[derive(Debug, Args)]
struct CommonArgs {
    /// The value of column x to be filtered in the database
    #[clap(short, long, value_parser)]
    x_value: Option<String>,
    /// The value of column y to be filtered in the database
    #[clap(short, long, value_parser)]
    y_value: Option<String>,
}

#[derive(Debug, Args)]
struct ArgsA {
    #[clap(flatten)]
    common_args: CommonArgs,
    /// Hard
    #[clap(short = 'H', long)]
    particular_a: bool,
}

#[derive(Debug, Args)]
struct ArgsB {
    // #[clap(subcommand)]
    // subcommand: ShowSubcommand,
    #[clap(flatten)]
    commmon_args: CommonArgs,
    /// Head
    #[clap(long)]
    particular_b: Option<u32>,
}

#[derive(Debug, Parser)]
pub struct UserInput {
    #[clap(subcommand)]
    command: MyCommand,
}

#[derive(Debug, Subcommand)]
enum MyCommand {
    /// A command description
    A(ArgsA),
    /// B command description
    B(ArgsB),
}

fn main() {
    dbg!(UserInput::parse_from("playground b --help".split(' ')));
}

唯一的区别是您可以在访问时多一级间接访问。

这种“缺点”带来的好处是您可以更轻松地传递 arguments 的部分内容，例如为ArgsA和ArgsB实施AsRef<CommonArgs> 。