fort/
lib.rs

1#![forbid(unsafe_code, future_incompatible, rust_2018_idioms)]
2#![deny(missing_debug_implementations, nonstandard_style)]
3
4use proc_macro::TokenStream;
5use quote::quote;
6use syn::{Error, Lit, Meta, NestedMeta, ReturnType};
7
8#[proc_macro_attribute]
9pub fn root(attr: TokenStream, item: TokenStream) -> TokenStream {
10    let input = syn::parse_macro_input!(item as syn::ItemFn);
11    let args = syn::parse_macro_input!(attr as syn::AttributeArgs);
12
13    let body = &input.block;
14    let attrs = &input.attrs;
15    let inputs = &input.sig.inputs;
16    let ret = &input.sig.output;
17
18    if input.sig.asyncness.is_none() {
19        let msg = "functions tagged with '#[fort::root]' should be declared as 'async'";
20        return Error::new_spanned(input.sig.fn_token, msg)
21            .to_compile_error()
22            .into();
23    } else if input.sig.ident != "main" {
24        let msg = "only the main function can be tagged with '#[fort::root]'";
25        return Error::new_spanned(input.sig.ident, msg)
26            .to_compile_error()
27            .into();
28    } else if inputs.len() != 1 {
29        let msg = "functions tagged with '#[fort::root]' should have one argument of type 'BastionContext'";
30        return Error::new_spanned(inputs, msg).to_compile_error().into();
31    } else if let ReturnType::Default = ret {
32        let msg = "functions tagged with '#[fort::root]' should return 'Result<(), ()>'";
33        return Error::new_spanned(ret, msg).to_compile_error().into();
34    }
35
36    // TODO: assert!( inputs == [`::bastion::BastionContext`] );
37    // TODO: assert!( ret == `::std::result::Result<(), ()>` );
38
39    let mut redundancy = 1;
40    for arg in args {
41        if let NestedMeta::Meta(Meta::NameValue(meta)) = arg {
42            let ident = meta.path.get_ident();
43            if ident.is_none() {
44                let msg = "must specify an ident";
45                return Error::new_spanned(meta, msg).to_compile_error().into();
46            }
47
48            let ident = ident.unwrap();
49            match ident.to_string().as_str() {
50                "redundancy" => {
51                    if let Lit::Int(n) = meta.lit {
52                        redundancy = n.base10_parse::<usize>().unwrap();
53                    } else {
54                        let msg = "'redundancy' should be a number";
55                        return Error::new_spanned(meta.lit, msg).to_compile_error().into();
56                    }
57                }
58                _ => {
59                    let msg = "unknown attribute";
60                    return Error::new_spanned(ident, msg).to_compile_error().into();
61                }
62            }
63        }
64    }
65
66    (quote! {
67        fn main() {
68            #(#attrs)*
69            async fn main(#inputs) #ret {
70                #body
71            }
72
73            bastion::Bastion::init();
74            bastion::Bastion::children(|children| {
75                children
76                    .with_exec(|ctx| main(ctx))
77                    .with_redundancy(#redundancy)
78            }).expect("Couldn't create the main children group.");
79
80            bastion::Bastion::start();
81            bastion::Bastion::block_until_stopped();
82        }
83    })
84    .into()
85}
fort/lib.rs

fort/
lib.rs
