main.rs

#[macro_use]
extern crate lazy_static;
extern crate regex;
extern crate reqwest;

use std::env;
use std::fs::File;
use std::io::prelude::*;
use regex::*;
use reqwest::Client;
use reqwest::Error;

fn get_redirected_url(url: &str) -> Option<String> {
    Client::new()
        .head(url)
        .send()
        .map(|resp| resp.url().as_str().to_string())
        .ok()
}

fn main() {
    let filename = "../tmcw.github.com/_posts/2017-07-01-recently.md";
    let mut f = File::open(filename).expect("file not found");
    let mut contents = String::new();
    f.read_to_string(&mut contents).expect(
        "something went wrong reading the file",
    );

    lazy_static! {
         static ref AMZN_RE: Regex = Regex::new(r"https?://amzn.to/([0-9A-Za-z]+)").unwrap();
         static ref ISBN1: Regex = Regex::new(
             r"https://www.amazon.com/(?:[A-Za-z\-]+)/dp/(\d{10})/").unwrap();
         static ref ISBN2: Regex = Regex::new(
             r"https://www.amazon.com/gp/product/(\d{10})/").unwrap();
     }
    let captures: Vec<_> = AMZN_RE.captures_iter(&contents).collect();

    for cap in captures {
        get_redirected_url(cap.get(0).unwrap().as_str()).and_then(|redirected_to| {
            let c1 = ISBN1.captures(&redirected_to);
            let c2 = ISBN2.captures(&redirected_to);
            c1.or(c2)
        });
        // .and_then(|capture| {
        //     let isbn = capture.get(1).unwrap().as_str();
        //     let worldcat_url = format!("http://www.worldcat.org/isbn/{}", isbn);
        //     get_redirected_url(&worldcat_url).map(|worldcat_permalink| {
        //         println!("worldcat permalink:\n{:?}", worldcat_permalink);
        //         // contents =
        //         //     contents.replace(capture.get(0).unwrap().as_str(), &worldcat_permalink);
        //     })
        // });
    }
}

   Compiling anticapitalist v0.1.0 (file:///Users/tmcw/p/anticapitalist)
warning: unused import: `std::env`
 --> main.rs:6:5
  |
6 | use std::env;
  |     ^^^^^^^^
  |
  = note: #[warn(unused_imports)] on by default

warning: unused import: `reqwest::Error`
  --> main.rs:11:5
   |
11 | use reqwest::Error;
   |     ^^^^^^^^^^^^^^

error[E0597]: `redirected_to` does not live long enough
  --> main.rs:43:9
   |
40 |             let c1 = ISBN1.captures(&redirected_to);
   |                                      ------------- borrow occurs here
...
43 |         });
   |         ^- borrowed value needs to live until here
   |         |
   |         `redirected_to` dropped here while still borrowed

error[E0597]: `redirected_to` does not live long enough
  --> main.rs:43:9
   |
41 |             let c2 = ISBN2.captures(&redirected_to);
   |                                      ------------- borrow occurs here
42 |             c1.or(c2)
43 |         });
   |         ^- borrowed value needs to live until here
   |         |
   |         `redirected_to` dropped here while still borrowed

error: aborting due to 2 previous errors

error: Could not compile `anticapitalist`.

To learn more, run the command again with --verbose.

Hi, thanks for sharing this, really. It came at the right time, when I was in the right mood, to play around with rust for the first time :)

I got it to compile by replacing c1.or(c2) with:

match c1.or(c2) {
    Some(c) => Some(c.get(1).unwrap().as_str().to_string()),
    None => None,
}

When returning c1 or c2 those both have references to redirected_to inside them. So passing along one of those makes it unclear who will clean it up (maybe you have to borrow it or something). The way I understand my fix is to finish using it by evaluating the regex and making a string that gets passed along. I believe it's the to_string that does this. What would have helped me was having my editor tell me exactly what type was returned in that chain in of functions, at this point I'm kind of guessing.

I've never written a big project in a non-gc language. This makes me curious how this all plays out in more complicated code. Again, thanks for sharing.

I think the problem is occurring because you're trying to "prematurely" end the lifetime of a borrowed reference (by implicitly calling drop on l43 when you close the expression). Even though @paulmach's suggestion works, you can also fix it if you:

• uncomment your code from l44 to l52
• delete l43
• insert }) as a new line on l47

Now it compiles and prints new Worldcat URLs:

for cap in captures {
    get_redirected_url(cap.get(0).unwrap().as_str()).and_then(|redirected_to| {
        let c1 = ISBN1.captures(&redirected_to);
        let c2 = ISBN2.captures(&redirected_to);
        c1.or(c2)
        .and_then(|capture| {
            let isbn = capture.get(1).unwrap().as_str();
            let worldcat_url = format!("http://www.worldcat.org/isbn/{}", isbn);
            get_redirected_url(&worldcat_url).map(|worldcat_permalink| {
                println!("worldcat permalink:\n{:?}", worldcat_permalink);
                // contents =
                // contents.replace(capture.get(0).unwrap().as_str(), &worldcat_permalink);
            })
        })
    });
}