nushell/src/commands/where_.rs

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

pub fn r#where(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"))
        }
    }
}