nushell/crates/nu-command/src/core_commands/alias.rs

use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EvaluationContext};
use nu_protocol::{Signature, SyntaxShape, Value};

pub struct Alias;

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

    fn usage(&self) -> &str {
        "Alias a command (with optional flags) to a new name"
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("alias")
            .required("name", SyntaxShape::String, "name of the alias")
            .required(
                "initial_value",
                SyntaxShape::Keyword(b"=".to_vec(), Box::new(SyntaxShape::Expression)),
                "equals sign followed by value",
            )
    }

    fn run(
        &self,
        _context: &EvaluationContext,
        call: &Call,
        _input: Value,
    ) -> Result<nu_protocol::Value, nu_protocol::ShellError> {
        Ok(Value::Nothing { span: call.head })
    }
}