fs-err is a drop-in replacement for std::fs that provides more helpful messages on errors. Extra information includes which operations was attempted and any involved paths.

Error Messages

Using std::fs, if this code fails:

let file = File::open("does not exist.txt")?;

The error message that Rust gives you isn’t very useful:

The system cannot find the file specified. (os error 2)

…but if we use fs-err instead, our error contains more actionable information:

failed to open file `does not exist.txt`
    caused by: The system cannot find the file specified. (os error 2)

Usage

fs-err’s API is the same as std::fs, so migrating code to use it is easy.

// use std::fs;
use fs_err as fs;

let contents = fs::read_to_string("foo.txt")?;

println!("Read foo.txt: {}", contents);

fs-err uses std::io::Error for all errors. This helps fs-err compose well with traits from the standard library like std::io::Read and crates that use them like serde_json:

use fs_err::File;

let file = File::open("my-config.json")?;

// If an I/O error occurs inside serde_json, the error will include a file path
// as well as what operation was being performed.
let decoded: Vec<String> = serde_json::from_reader(file)?;

println!("Program config: {:?}", decoded);