Refactoring error handling in Rust

00_main.rs

// main.rs
mod request;

use request::request;

fn main() {
    match request() {
        Ok(text) => println!("{}", text),
        Err(err) => println!("{}", err)
    }
}

01_request.rs

extern crate reqwest;

use reqwest::StatusCode;

pub fn request() -> Result<String, String> {
    match reqwest::get("https://www.rust-lang.org/en-US") {
        Ok(mut r) => match r.status() {
            StatusCode::OK => match r.text() {
                Ok(t) => return Ok(t),
                Err(_) => return Err("Failed to extract text from response".to_string())
            },
            s => return Err(format!("Invalid Status Code: {:?}", s)),
        },
        Err(_) => return Err("Request Failed".to_string()),
    }
}

10_main.rs

// main.rs
mod request;
mod error;

use request::request;

fn main() {
    match request() {
        Ok(text) => println!("{}", text),
        Err(err) => println!("{}", err),
    }
}

11_request.rs

// request.rs
extern crate reqwest;

use error::Error;

type RequestResult<T> = Result<T, Error>;

pub fn request() -> RequestResult<String> {
    let mut res =
        reqwest::get("http://sample.com/")?;
    if !res.status().is_success() {
        let err = Error::InvalidStatusCode { code: res.status() };
        return Err(err);
    }
    return Ok(res.text()?);
}

12_error.rs

extern crate reqwest;

use std::fmt;

pub enum Error {
    HttpError(reqwest::Error),
    InvalidStatusCode { code: reqwest::StatusCode },
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::HttpError(ref e) => writeln!(f, "Http Request Failed. {}", e),
            Error::InvalidStatusCode { code: c } => writeln!(f, "Invalid Status Code. {}", c),
        }
    }
}

impl From<reqwest::Error> for Error {
    fn from(e: reqwest::Error) -> Error {
        Error::HttpError(e)
    }
}

01_request.rs is ugly because of the conditional logics. It can be refactored by defining RequestResult as you see in 11_request.rs, so you can use get.(...)?, text(...)? without the error handlings.