nushell/crates/nu-cli/src/commands/alias.rs

use crate::commands::{Example, WholeStreamCommand};
use crate::context::CommandRegistry;
use crate::prelude::*;
use nu_errors::ShellError;
use nu_protocol::{hir::Block, CommandAction, ReturnSuccess, Signature, SyntaxShape, Value};
use nu_source::Tagged;

pub struct Alias;

#[derive(Deserialize)]
pub struct AliasArgs {
    pub name: Tagged<String>,
    pub args: Vec<Value>,
    pub block: Block,
}

impl WholeStreamCommand for Alias {
    fn name(&self) -> &str {
        "alias"
    }

    fn signature(&self) -> Signature {
        Signature::build("alias")
            .required("name", SyntaxShape::String, "the name of the alias")
            .required("args", SyntaxShape::Table, "the arguments to the alias")
            .required(
                "block",
                SyntaxShape::Block,
                "the block to run as the body of the alias",
            )
    }

    fn usage(&self) -> &str {
        "Define a shortcut for another command."
    }

    fn run(
        &self,
        args: CommandArgs,
        registry: &CommandRegistry,
    ) -> Result<OutputStream, ShellError> {
        args.process(registry, alias)?.run()
    }

    fn examples(&self) -> &[Example] {
        &[Example {
            description: "Some people prefer to write one letter instead of two",
            example: "alias l [x] { ls $x }",
        }]
    }
}

pub fn alias(
    AliasArgs {
        name,
        args: list,
        block,
    }: AliasArgs,
    _: RunnableContext,
) -> Result<OutputStream, ShellError> {
    let stream = async_stream! {
        let mut args: Vec<String> = vec![];
        for item in list.iter() {
            if let Ok(string) = item.as_string() {
                args.push(format!("${}", string));
            } else {
                yield Err(ShellError::labeled_error("Expected a string", "expected a string", item.tag()));
            }
        }
        yield ReturnSuccess::action(CommandAction::AddAlias(name.to_string(), args, block.clone()))
    };

    Ok(stream.to_output_stream())
}