try_map

try_map and flip methods for Option. These allow more ergonomic error handling when mapping functions that return Result over Option.

How to use:

Add to Cargo.toml:

[dependencies]
try_map = "0.1"

Bring the extension traits to the scope in your code: (FallibleMapExt is for enabling try_map and FlipResultExt is for enabling flip.)

use try_map::{FallibleMapExt, FlipResultExt};

Use the try_map and flip methods like a boss!

    fn try_map_example() -> Result<Option<i32>, &'static str> {
        let x = Some(42)
            .try_map(|x| Ok(x + 1))?
            .try_map(|x| Ok(x + 1))?
            .try_map(|x| if true { Err("oh noes") } else { Ok(x + 1) })?
            .try_map(|x| Ok(x + 1))?;
    
        Ok(x)
    }
    assert_eq!(try_map_example(), Err("oh noes"));

    fn flip_example() -> Result<Option<i32>, &'static str> {
        let x = Some(42)
            .map(|x| Ok(x + 1)).flip()?
            .map(|x| Ok(x + 1)).flip()?
            .map(|x| if true { Err("oh noes") } else { Ok(x + 1) }).flip()?
            .map(|x| Ok(x + 1)).flip()?;
    
        Ok(x)
    }
    assert_eq!(flip_example(), Err("oh noes"));

What else?

There is an open issue in the Rust RFC repo suggesting bringing these helper methods to the standard library: https://github.com/rust-lang/rfcs/issues/1815 Thanks for @killercup for suggesting implementing these in a 3rd party crate. This way they are immediately useful. (My claim is that they would be still useful in the standard library, though!)