nushell/src/commands/where_.rs

use crate::errors::ShellError;
use crate::object::base::find;
use crate::prelude::*;
use derive_new::new;

#[derive(new)]
pub struct Where;

impl crate::Command for Where {
    fn run(&self, args: CommandArgs<'caller>) -> Result<VecDeque<ReturnValue>, ShellError> {
        if args.args.is_empty() {
            return Err(ShellError::string("select requires a field"));
        }

        let field: Result<String, _> = args.args[0].as_string();
        let field = field?;

        match args.args[1] {
            Value::Primitive(Primitive::Operator(ref operator)) => {
                let objects = args
                    .input
                    .iter()
                    .filter(|item| find(&item, &field, operator, &args.args[2]))
                    .map(|item| ReturnValue::Value(item.copy()))
                    .collect();

                Ok(objects)
            }
            ref x => {
                println!("{:?}", x);
                Err(ShellError::string("expected a comparison operator"))
            }
        }
    }
}