RailsGun

RailsGun or Railgun, call it how you want it. This crate add a lot of small but valuable functionality to the existing Rail paradigm in rust.

If you are used to using rails in rust, you know what it's all about! If its the first time you hear about it, I would highly suggest you read the following Railway Oriented Programming; In short its a programming style that I have found over multiple projects and services to reduce the errors.

This crate supplies you with some extra missing tools and simplifications as follows:

tap, tap_err, tap_ref, tap_err_ref

This is an excellent little trait that adds the ability to "tap" the contents. This means that you can get a copy/clone of the original content that you can use for analysis or other destructive operations without actually touching the original.

Note: tap_ref and tap_err_ref unfortunatly is just a reference so destructive actions should not be taken.

merge, merge2, merge3, merge4

This is for merging multiple results. If you have worked with rails before you have probably tried the following:

use railsgun::Merge;

fn func_xyz(x: u32, y: u32, z: u32) -> Result<u32,u32> {
    Ok( x + y + z)
}

let x = Ok(1);
let y = Ok(2);
let z = Ok(3);

x.and_then(|var_x|
    y.and_then(|var_y|
        z.and_then(|var_z|
            func_xyz(var_x, var_y, var_z)
        )
    )
).ok();

This is a hideous method of combining three results, you could split it out into multiple functions, but at times that is very excessive. Merge supplies you with superior functionality for this.

use railsgun::Merge;

fn func_xyz(x: u32, y: u32, z: u32) -> Result<u32,u32> {
    Ok( x + y + z)
}

# async fn run() -> () {
let x = Ok(1);
let y = Ok(2);
let z = Ok(3);
x.merge2(y, z, |var_x, var_y, var_z| func_xyz(var_x, var_y, var_z)).ok();
# }

As you can see, this simplifies the rail significantly and makes it more readable/maintainable.

Trait BlockInPlaceResult

This trait requires your system to currently be running inside a Tokio thread as it requires multithreading. That said, it adds some interesting capabilities on top of the result. If the following annoys you:

async fn my_async_fn() -> Result<String, String> {
    Ok("Something awesome".to_string())
}

# async fn run() -> () {
my_async_fn().await.map(|t| println!("{}", t)).ok();
# };

This allows you to cut corners by:

use railsgun::BlockInPlaceResult;

async fn my_async_fn() -> Result<String, String> {
    Ok("Something awesome".to_string())
}

# async fn run() -> () {
my_async_fn().map(|t| format!("{}", t)).ok();
# };

Please note this is using tokio block_in_place for execution.

AsyncResult

As the name describes, this is an AsyncResult. It has almost everything that a Result has, and some other extra features. This allows you to execute async functions and code inside your rail by doing the following

use railsgun::AsyncResult::{self, *};

async fn do_something(t: &str) -> AsyncResult<&str,&str> {
    Ok(t)
}

# async fn run() -> () {
let x = Ok("foo");

x.async_and_then(|t| do_something(t)).await
    .async_and_then(|t| async move { Ok(t) }).await
    .ok();
# };

Of course, this is not the prettiest thing, but it allows the system to keep to its rail and keep processing without moving in and out of the rails.

Of course, this also comes with From/Into implementations for Result and even an into_async/into_sync implementation that is more descriptive when converting between AsyncResult and Result.

Todo

There is a significant need for more documentation on the trait and others as this library has been in my private stack for a long time and did get the doc-care it needed.

1. tap needs doc
2. merge needs doc
3. Implement BlockInPlace for AsyncResult
4. More unit tests are needed.

Please open a ticket for more ideas!

Contribution

Feel free to contribute to the project. Currently, the project is hosted on both GitHub and my private GitLab. The main repository is the GitLab repository, where all of the pipelines and all of my projects exist.

License

The MIT License (MIT)

Copyright © 2021

Permission is hereby granted, free of charge, to any person obtaining a copy of this Software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.