Is there a way to simplify converting an Option into a Result without a macro?

Question

I have something like this (the real function is Ini::Section::get from rust-ini):

impl Foo {     pub fn get<K>(&'a mut self, key: &K) -> Option<&'a str>     where         K: Hash + Eq,     {         // ...     } } 

I have to call it several times:

fn new() -> Result<Boo, String> {     let item1 = match section.get("item1") {         None => return Result::Err("no item1".to_string()),         Some(v) => v,     };     let item2 = match section.get("item2") {         None => return Result::Err("no item2".to_string()),         Some(v) => v,     }; } 

To remove code bloat, I can write a macro like this:

macro_rules! try_ini_get {     ($e:expr) => {         match $e {             Some(s) => s,             None => return Result::Err("no ini item".to_string()),         }     } } 

Is there any way to remove the code duplication without this macro implementation?

Answer 1

The ok_or and ok_or_else methods convert Options to Results, and the ? operator automates the boilerplate associated with early Err returns.

You could do something like:

fn new() -> Result<Boo, String> {     let item1 = section.get("item1").ok_or("no item1")?;     let item2 = section.get("item2").ok_or("no item2")?;     // whatever processing...     Ok(final_result) } 

Answer 2

If you're using the crate anyhow you can import the anyhow::Context trait which adds the .context method on Options to turn them into anyhow::Results:

use anyhow::{Result, Context};  fn new() -> Result<Boo> {     let item1 = section.get("item1").context("no item1")?;     let item2 = section.get("item2").context("no item2")?;     // whatever processing...     Ok(final_result) }