base on Flexible concrete Error type built on std::error::Error Anyhow&ensp;¯\\\_(°ペ)\_/¯ ========================== [<img alt="github" src="https://img.shields.io/badge/github-dtolnay/anyhow-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/anyhow) [<img alt="crates.io" src="https://img.shields.io/crates/v/anyhow.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/anyhow) [<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-anyhow-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/anyhow) [<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/anyhow/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/anyhow/actions?query=branch%3Amaster) This library provides [`anyhow::Error`][Error], a trait object based error type for easy idiomatic error handling in Rust applications. [Error]: https://docs.rs/anyhow/1.0/anyhow/struct.Error.html ```toml [dependencies] anyhow = "1.0" ``` *Compiler support: requires rustc 1.39+* <br> ## Details - Use `Result<T, anyhow::Error>`, or equivalently `anyhow::Result<T>`, as the return type of any fallible function. Within the function, use `?` to easily propagate any error that implements the [`std::error::Error`] trait. ```rust use anyhow::Result; fn get_cluster_info() -> Result<ClusterMap> { let config = std::fs::read_to_string("cluster.json")?; let map: ClusterMap = serde_json::from_str(&config)?; Ok(map) } ``` [`std::error::Error`]: https://doc.rust-lang.org/std/error/trait.Error.html - Attach context to help the person troubleshooting the error understand where things went wrong. A low-level error like "No such file or directory" can be annoying to debug without more context about what higher level step the application was in the middle of. ```rust use anyhow::{Context, Result}; fn main() -> Result<()> { ... it.detach().context("Failed to detach the important thing")?; let content = std::fs::read(path) .with_context(|| format!("Failed to read instrs from {}", path))?; ... } ``` ```console Error: Failed to read instrs from ./path/to/instrs.json Caused by: No such file or directory (os error 2) ``` - Downcasting is supported and can be by value, by shared reference, or by mutable reference as needed. ```rust // If the error was caused by redaction, then return a // tombstone instead of the content. match root_cause.downcast_ref::<DataStoreError>() { Some(DataStoreError::Censored(_)) => Ok(Poll::Ready(REDACTED_CONTENT)), None => Err(error), } ``` - If using Rust &ge; 1.65, a backtrace is captured and printed with the error if the underlying error type does not already provide its own. In order to see backtraces, they must be enabled through the environment variables described in [`std::backtrace`]: - If you want panics and errors to both have backtraces, set `RUST_BACKTRACE=1`; - If you want only errors to have backtraces, set `RUST_LIB_BACKTRACE=1`; - If you want only panics to have backtraces, set `RUST_BACKTRACE=1` and `RUST_LIB_BACKTRACE=0`. [`std::backtrace`]: https://doc.rust-lang.org/std/backtrace/index.html#environment-variables - Anyhow works with any error type that has an impl of `std::error::Error`, including ones defined in your crate. We do not bundle a `derive(Error)` macro but you can write the impls yourself or use a standalone macro like [thiserror]. ```rust use thiserror::Error; #[derive(Error, Debug)] pub enum FormatError { #[error("Invalid header (expected {expected:?}, got {found:?})")] InvalidHeader { expected: String, found: String, }, #[error("Missing attribute: {0}")] MissingAttribute(String), } ``` - One-off error messages can be constructed using the `anyhow!` macro, which supports string interpolation and produces an `anyhow::Error`. ```rust return Err(anyhow!("Missing attribute: {}", missing)); ``` A `bail!` macro is provided as a shorthand for the same early return. ```rust bail!("Missing attribute: {}", missing); ``` <br> ## No-std support In no_std mode, almost all of the same API is available and works the same way. To depend on Anyhow in no_std mode, disable our default enabled "std" feature in Cargo.toml. A global allocator is required. ```toml [dependencies] anyhow = { version = "1.0", default-features = false } ``` With versions of Rust older than 1.81, no_std mode may require an additional `.map_err(Error::msg)` when working with a non-Anyhow error type inside a function that returns Anyhow's error type, as the trait that `?`-based error conversions are defined by is only available in std in those old versions. <br> ## Comparison to failure The `anyhow::Error` type works something like `failure::Error`, but unlike failure ours is built around the standard library's `std::error::Error` trait rather than a separate trait `failure::Fail`. The standard library has adopted the necessary improvements for this to be possible as part of [RFC 2504]. [RFC 2504]: https://github.com/rust-lang/rfcs/blob/master/text/2504-fix-error.md <br> ## Comparison to thiserror Use Anyhow if you don't care what error type your functions return, you just want it to be easy. This is common in application code. Use [thiserror] if you are a library that wants to design your own dedicated error type(s) so that on failures the caller gets exactly the information that you choose. [thiserror]: https://github.com/dtolnay/thiserror <br> #### License ^{Licensed under either of <a href="LICENSE-APACHE">Apache License, Version 2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.} <br> _{Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.} ", Assign "at most 3 tags" to the expected json: {"id":"10316","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"