[−][src]Crate snafu
SNAFU
SNAFU is a library to easily assign underlying errors into domain-specific errors while adding context. For detailed information, please see the user's guide.
Quick example
This example mimics a (very poor) authentication process that
opens a file, writes to a file, and checks the user's ID. While
two of our operations involve an io::Error
,
these are different conceptual errors to us.
SNAFU creates context selectors mirroring each error
variant. These are used with the context
method to provide ergonomic error handling.
use snafu::{Snafu, ResultExt, Backtrace, ErrorCompat, ensure}; use std::{fs, path::{Path, PathBuf}}; #[derive(Debug, Snafu)] enum Error { #[snafu(display("Could not open config from {}: {}", filename.display(), source))] OpenConfig { filename: PathBuf, source: std::io::Error }, #[snafu(display("Could not save config to {}: {}", filename.display(), source))] SaveConfig { filename: PathBuf, source: std::io::Error }, #[snafu(display("The user id {} is invalid", user_id))] UserIdInvalid { user_id: i32, backtrace: Backtrace }, } type Result<T, E = Error> = std::result::Result<T, E>; fn log_in_user<P>(config_root: P, user_id: i32) -> Result<bool> where P: AsRef<Path>, { let config_root = config_root.as_ref(); let filename = &config_root.join("config.toml"); let config = fs::read(filename).context(OpenConfig { filename })?; // Perform updates to config fs::write(filename, config).context(SaveConfig { filename })?; ensure!(user_id == 42, UserIdInvalid { user_id }); Ok(true) } fn log_in() { match log_in_user(CONFIG_DIRECTORY, USER_ID) { Ok(true) => println!("Logged in!"), Ok(false) => println!("Not logged in!"), Err(e) => { eprintln!("An error occurred: {}", e); if let Some(backtrace) = ErrorCompat::backtrace(&e) { println!("{}", backtrace); } } } }
Re-exports
pub use snafu_derive::Snafu; |
Modules
guide | SNAFU user's guide |
Macros
ensure | Ensure a condition is true. If it is not, return from the function with an error. |
Structs
Backtrace | A backtrace starting from the beginning of the thread. |
Context | A combination of an underlying error and additional information about the error. It is not expected for users of this crate to interact with this type. |
NoneError | A temporary error type used when converting an |
Traits
ErrorCompat | Backports changes to the |
OptionExt | Additions to |
ResultExt | Additions to |