rust-script-ext

Opinionated set of extensions for use with rust-script or cargo script.

Using rust-script to run Rust like a shell script is great! This crate provides an opinionated set of extensions tailored towards common patterns in scripts. These patterns include file reading, argument parsing, error handling. The goal is for script writers to focus on the business logic, not implementing parsers, handling errors, parsing arguments, etc.

Using rust-script

$ cargo install rust-script
..
$ cat ./template-rust-script.rs
#!/usr/bin/env -S rust-script -c
//! You might need to chmod +x your script!
//! ```cargo
//! [dependencies.rust-script-ext]
//! git = "https://github.com/kurtlawrence/rust-script-ext"
//! rev = "2a16a21f150e7e36725195d09e4b08ebbe944548"
//! ```
// See <https://kurtlawrence.github.io/rust-script-ext/rust_script_ext/> for documentation
use rust_script_ext::prelude::*;

fn main() -> Result<()> {
    // fastrand comes from rust_script_ext::prelude::*
    let n = std::iter::repeat_with(|| fastrand::u32(1..=100))
        .take(5)
        .collect::<Vec<_>>();

    println!("Here's 5 random numbers: {n:?}");
    Ok(())
}
$ ./template-rust-script.rs
Here's 5 random numbers: [28, 97, 9, 23, 58]

Using cargo script

$ cat ./template-cargo-script.rs
#!/usr/bin/env -S cargo +nightly -Zscript
---
[dependencies.rust-script-ext]
git = "https://github.com/kurtlawrence/rust-script-ext"
rev = "2a16a21f150e7e36725195d09e4b08ebbe944548"
---
// You might need to chmod +x your script!
// See <https://kurtlawrence.github.io/rust-script-ext/rust_script_ext/> for documentation
use rust_script_ext::prelude::*;

fn main() -> Result<()> {
    // fastrand comes from rust_script_ext::prelude::*
    let n = std::iter::repeat_with(|| fastrand::u32(1..=100))
        .take(5)
        .collect::<Vec<_>>();

    println!("Here's 5 random numbers: {n:?}");
    Ok(())
}
$ ./template-cargo-script.rs
Here's 5 random numbers: [91, 65, 32, 75, 39]

Template Quickstart

template-rust-script.rs contains a simple scaffold for use with rust-script:

curl -L https://github.com/kurtlawrence/rust-script-ext/raw/main/template-rust-script.rs -o my-script.rs
chmod +x my-script.rs
./my-script.rs

template-cargo-script.rs contains a simple scaffold for use with cargo-script:

curl -L https://github.com/kurtlawrence/rust-script-ext/raw/main/template-cargo-script.rs -o my-script.rs
chmod +x my-script.rs
./my-script.rs

cargo script does not (currently) set up an isolated environment when running the script, which can cause errors if the script lives within a Rust crate. I recommend using rust-script instead.

What's included?

What rust-script-ext provides is continually evolving. It is best to review the API documentation. At a high level, the crate provides helpers and data structures which are common in a scripting environment, such as easy error handling, file reading, serialisation/deserialisation, etc. If you find something lacking, I encourage you to open a PR!

Language Server Support

Note: only tested with rust-script.

rscls works as a middle-man LSP between rust-analyzer and rust-script. Below are instructions for getting LSP support using Neovim.

First, ensure you have rscls installed.

cargo install rscls

Next, add the following to your configuration. Note this is for Neovim LSP config.

-- Rust script LSP support through rscls
local lsp_configs = require 'lspconfig.configs'
if not lsp_configs.rscls then
	lsp_configs.rscls = {
		default_config = {
			cmd = { 'rscls' },
		    filetypes = { 'rustscript' },
		    root_dir = function(fname)
		        return require'lspconfig'.util.path.dirname(fname)
		    end,
		},
	}
end
require 'lspconfig'.rscls.setup {}

Then, when you are wanting LSP support in a Rust file, set the file type to rustscript with a command.

:set filetype=rustscript

I generally do not bother with LSP support for small scripts, but it comes in handy for more complex ones! Note that it will take a little bit to spool up the server and compile the script.

Versioning

Versioning does not follow semver as would a normal crate. Instead, it is best to pin a script to a revision number of the repository. As most scripts are ephemeral, or at least not pushed to a large userbase, this encourages a simple versioning scheme where you will be mostly guaranteed that when you run the script, it will compile! Leaving off the revision number should also be fairly safe (cargo should lock it to a revision), but moving the script to another system or clearing the cache could potentially break compilation.