remove-async-await

A procedural macro to make an async function blocking by removing async and awaits. Useful for crates with practically identical blocking and async implementations, aside from having to use .await on some function calls.

Adding as a dependency

It is recommended to point the dependency to 1.0 so you get any bug fixes I have to make:

[dependencies]
remove-async-await = "1.0"

Example

This example assumes you want to keep your async API behind an optional feature called async.

#[cfg_attr(not(feature = "async"), remove_async_await::remove_async_await)]
async fn get_string() -> String {
    "hello world".to_owned()
}

#[cfg_attr(not(feature = "async"), remove_async_await::remove_async_await)]
pub async fn print() {
    let string = get_string().await;
    println!("{}", string);
}

In this example, if the async feature is not used, it would expand to this:

fn get_string() -> String {
    "hello world".to_owned()
}

pub fn print() {
    let string = get_string();
    println!("{}", string);
}

However, if the async feature is used, the code will be unaffected.

You can find more examples in the tests/ directory.

remove_async_await_string

There are 2 macros this library provides:

1. remove_async_await: The one you should almost always use. Uses syn to parse rust code and remove async from functions and await from expressions. Currently, it can only take a function as an input.
2. remove_async_await_string: You should only use this one if remove_async_await doesn't work for your use case. This is the "dumb macro"; it literally just removes all occurrences of async and .await from the string representation of the input. This means that while it might work with things other than functions, you shouldn't use it because if a function or variable name contains "async" or ".await", your code will break.

Known issues

Here is a list of known issues/limitations that I probably won't fix (PRs are welcome!):

• Issue: .await is not removed when calling a macro

  Workarounds:

  • Move the expression using .await to a local variable.

    Example:

    #[remove_async_await::remove_async_await)]
    async fn issue() {
        println!("{}", get_string().await); // `.await` will not be removed
    }
    
    #[remove_async_await::remove_async_await)]
    async fn workaround() {
        let string = get_string().await; // `.await` **will** be removed
        println!("{}", string);
    }
    

  • Use remove_async_await_string (read docs for more info, such as potential bad side effects)

    Example:

    #[remove_async_await::remove_async_await)]
    async fn issue() {
        println!("{}", get_string().await); // `.await` will not be removed
    }
    
    #[remove_async_await::remove_async_await_string)]
    async fn workaround() {
        println!("{}", get_string().await); // `.await` **will** be removed
    }
    

If you want me to add an issue to this list (or fix the issue), please create a GitHub issue!