Trait snafu::futures::try_stream::TryStreamExt

source · 
pub trait TryStreamExt: TryStream + Sized {
    fn context<C, E>(self, context: C) -> Context<Self, C, E>
    where
        C: IntoError<E, Source = Self::Error> + Clone,
        E: Error + ErrorCompat;
    fn with_context<F, C, E>(self, context: F) -> WithContext<Self, F, E>
    where
        F: FnMut(&mut Self::Error) -> C,
        C: IntoError<E, Source = Self::Error>,
        E: Error + ErrorCompat;
    fn whatever_context<S, E>(self, context: S) -> WhateverContext<Self, S, E>
    where
        S: Into<String>,
        E: FromString;
    fn with_whatever_context<F, S, E>(
        self,
        context: F
    ) -> WithWhateverContext<Self, F, E>
    where
        F: FnMut(&mut Self::Error) -> S,
        S: Into<String>,
        E: FromString;
}
Expand description

Additions to [TryStream].

Required Methods§

Extend a [TryStream]’s error with additional context-sensitive information.

use futures::TryStream;
use snafu::prelude::*;

#[derive(Debug, Snafu)]
enum Error {
    Authenticating {
        user_name: String,
        user_id: i32,
        source: ApiError,
    },
}

fn example() -> impl TryStream<Ok = i32, Error = Error> {
    stock_prices().context(AuthenticatingSnafu {
        user_name: "admin",
        user_id: 42,
    })
}

fn stock_prices() -> impl TryStream<Ok = i32, Error = ApiError> {
    /* ... */
}

Note that the context selector will call Into::into on each field, so the types are not required to exactly match.

Extend a [TryStream]’s error with lazily-generated context-sensitive information.

use futures::TryStream;
use snafu::prelude::*;

#[derive(Debug, Snafu)]
enum Error {
    Authenticating {
        user_name: String,
        user_id: i32,
        source: ApiError,
    },
}

fn example() -> impl TryStream<Ok = i32, Error = Error> {
    stock_prices().with_context(|_| AuthenticatingSnafu {
        user_name: "admin",
        user_id: 42,
    })
}

fn stock_prices() -> impl TryStream<Ok = i32, Error = ApiError> {
    /* ... */
}

Note that this may not be needed in many cases because the context selector will call Into::into on each field.

Extend a [TryStream]’s error with information from a string.

The target error type must implement FromString by using the #[snafu(whatever)] attribute. The premade Whatever type is also available.

In many cases, you will want to use with_whatever_context instead as it is only called in case of error. This method is best suited for when you have a string literal.

use futures::TryStream;
use snafu::{prelude::*, Whatever};

fn example() -> impl TryStream<Ok = i32, Error = Whatever> {
    stock_prices().whatever_context("Couldn't get stock prices")
}

fn stock_prices() -> impl TryStream<Ok = i32, Error = ApiError> {
    /* ... */
}

Extend a [TryStream]’s error with information from a lazily-generated string.

The target error type must implement FromString by using the #[snafu(whatever)] attribute. The premade Whatever type is also available.

use futures::TryStream;
use snafu::{prelude::*, Whatever};

fn example(symbol: &'static str) -> impl TryStream<Ok = i32, Error = Whatever> {
    stock_prices(symbol)
        .with_whatever_context(move |_| format!("Couldn't get stock prices for {}", symbol))
}

fn stock_prices(symbol: &'static str) -> impl TryStream<Ok = i32, Error = ApiError> {
    /* ... */
}

Implementors§