Support configuration from Rocket.toml

[hugebubu]

Is it a good idea to have the configuration in Rocket.toml instead of a separated file?
I will be happy to make a PR :)

[ELD]

@hugebubu I like this idea and would definitely be open to accepting a PR that accomplishes this. Happy to mentor/advise/assist in any way desired, as well :)

[blackghost1987]

Just an FYI for anyone wandering here from Google: This is already possible! (at least with Rocket 0.5.0-rc1) It also works with "Fairing" mode, which was a bit surprising to me, because I thought you can't get the config before attaching the fairing, but you totally can!

The idea is to get the config from a partially built rocket instance, instantiate cors, then attach it to finish building. Here's how to do it:

let partial_rocket = rocket::build()
    .mount(........);
    
let cors_config: CorsOptions = partial_rocket.figment().focus("cors").extract().expect("missing CORS config");
let cors_fairing = cors_config.to_cors().expect("CORS init failed");

let final_rocket = partial_rocket.attach(cors_fairing);

// do the launch and the rest

The TOML deserialization of the CorsOptions struct was a bit tricky, especially because all the externally tagged enums and newtypes, but I've got it working, here's an example:

[default.cors]
allowed_methods = ["Get", "Post", "Put", "Patch"]
allow_credentials = true

[default.cors.allowed_origins.Some]
exact = ["http://localhost:4200", "http://localhost:8080"]

[default.cors.allowed_headers]
Some = [
    ["Authorization"],
    ["Accept"],
    ["content-type"]
]

I'm not sure this is still relevant to you @hugebubu , but I hope this helps someone.