Rust custom error

This crate contains a macro that should make it easier to define custom errors without having to write a lot of boilerplate code.

The custom_error! macro included in this crate takes a type name and a list of possible errors and generates a rust enumeration for all the cases, together with the required impl blocks implementing std::error::Error and std::fmt::Display.

You can now write

rust custom_error!(MyError Unknown{code:u8} = "unknown error with code {code}.", Err41 = "Sit by a lake" );

instead of

```rust

[derive(Debug)]

enum MyError { Unknown { code: u8 }, Err41, }

impl std::error::Error for MyError {}

impl std::fmt::Display for MyError { fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { match self { MyError::Unknown { code } => write!(f, "unknown error with code {}." , code), MyError::Err41 => write!(f, "Sit by a lake") } } } ```

Examples

Simple error

```rust extern crate customerror; use customerror::custom_error;

custom_error!(MyError Bad = "Something bad happened", Terrible = "This is a very serious error!!!" );

asserteq!("Something bad happened", MyError::Bad.tostring()); asserteq!("This is a very serious error!!!", MyError::Terrible.tostring()); ```

Custom error with parameters

```rust extern crate customerror; use customerror::custom_error;

custom_error!(SantaError BadChild{name:String, foolishness:u8} = "{name} has been bad {foolishness} times this year", TooFar = "The location you indicated is too far from the north pole", InvalidReindeer{legs:u8} = "The reindeer has {legs} legs" );

asserteq!( "Thomas has been bad 108 times this year", SantaError::BadChild{ name: "Thomas".into(), foolishness: 108 }.tostring());

asserteq!( "The location you indicated is too far from the north pole", SantaError::TooFar.tostring() );

asserteq!( "The reindeer has 8 legs", SantaError::InvalidReindeer{legs:8}.tostring() ); ```