cargo 0.33.0

Cargo, a package manager for Rust.
Documentation 
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use curl;
use git2;

use failure::Error;

use util::Config;
use util::errors::{CargoResult, HttpNot200};

pub struct Retry<'a> {
    config: &'a Config,
    remaining: u32,
}

impl<'a> Retry<'a> {
    pub fn new(config: &'a Config) -> CargoResult<Retry<'a>> {
        Ok(Retry {
            config,
            remaining: config.get::<Option<u32>>("net.retry")?.unwrap_or(2),
        })
    }

    pub fn try<T>(&mut self, f: impl FnOnce() -> CargoResult<T>)
        -> CargoResult<Option<T>>
    {
        match f() {
            Err(ref e) if maybe_spurious(e) && self.remaining > 0 => {
                let msg = format!(
                    "spurious network error ({} tries \
                     remaining): {}",
                    self.remaining, e
                );
                self.config.shell().warn(msg)?;
                self.remaining -= 1;
                Ok(None)
            }
            other => other.map(Some),
        }
    }
}

fn maybe_spurious(err: &Error) -> bool {
    for e in err.iter_chain() {
        if let Some(git_err) = e.downcast_ref::<git2::Error>() {
            match git_err.class() {
                git2::ErrorClass::Net | git2::ErrorClass::Os => return true,
                _ => (),
            }
        }
        if let Some(curl_err) = e.downcast_ref::<curl::Error>() {
            if curl_err.is_couldnt_connect()
                || curl_err.is_couldnt_resolve_proxy()
                || curl_err.is_couldnt_resolve_host()
                || curl_err.is_operation_timedout()
                || curl_err.is_recv_error()
            {
                return true;
            }
        }
        if let Some(not_200) = e.downcast_ref::<HttpNot200>() {
            if 500 <= not_200.code && not_200.code < 600 {
                return true;
            }
        }
    }
    false
}

/// Wrapper method for network call retry logic.
///
/// Retry counts provided by Config object `net.retry`. Config shell outputs
/// a warning on per retry.
///
/// Closure must return a `CargoResult`.
///
/// # Examples
///
/// ```ignore
/// use util::network;
/// cargo_result = network::with_retry(&config, || something.download());
/// ```
pub fn with_retry<T, F>(config: &Config, mut callback: F) -> CargoResult<T>
where
    F: FnMut() -> CargoResult<T>,
{
    let mut retry = Retry::new(config)?;
    loop {
        if let Some(ret) = retry.try(&mut callback)? {
            return Ok(ret)
        }
    }
}
#[test]
fn with_retry_repeats_the_call_then_works() {
    //Error HTTP codes (5xx) are considered maybe_spurious and will prompt retry
    let error1 = HttpNot200 {
        code: 501,
        url: "Uri".to_string(),
    }.into();
    let error2 = HttpNot200 {
        code: 502,
        url: "Uri".to_string(),
    }.into();
    let mut results: Vec<CargoResult<()>> = vec![Ok(()), Err(error1), Err(error2)];
    let config = Config::default().unwrap();
    let result = with_retry(&config, || results.pop().unwrap());
    assert_eq!(result.unwrap(), ())
}

#[test]
fn with_retry_finds_nested_spurious_errors() {
    use util::CargoError;

    //Error HTTP codes (5xx) are considered maybe_spurious and will prompt retry
    //String error messages are not considered spurious
    let error1 = CargoError::from(HttpNot200 {
        code: 501,
        url: "Uri".to_string(),
    });
    let error1 = CargoError::from(error1.context("A non-spurious wrapping err"));
    let error2 = CargoError::from(HttpNot200 {
        code: 502,
        url: "Uri".to_string(),
    });
    let error2 = CargoError::from(error2.context("A second chained error"));
    let mut results: Vec<CargoResult<()>> = vec![Ok(()), Err(error1), Err(error2)];
    let config = Config::default().unwrap();
    let result = with_retry(&config, || results.pop().unwrap());
    assert_eq!(result.unwrap(), ())
}