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//! A procedural macro for Rust that allows you to ensure that functions (e.g. //! unit tests) are not running at the same time. //! //! This is achieved by acquiring a mutex at the beginning of the annotated //! function. //! //! Different functions can synchronize on different mutexes. That's why a //! static mutex reference must be passed to the `nonparallel` annotation. //! //! ## Usage //! //! ```rust //! use std::sync::Mutex; //! use lazy_static::lazy_static; //! use nonparallel::nonparallel; //! //! // Create two locks //! lazy_static! { static ref MUT_A: Mutex<()> = Mutex::new(()); } //! lazy_static! { static ref MUT_B: Mutex<()> = Mutex::new(()); } //! //! // Mutually exclude parallel runs of functions using those two locks //! //! #[nonparallel(MUT_A)] //! fn function_a1() { //! // This will not run in parallel to function_a2 //! } //! //! #[nonparallel(MUT_A)] //! fn function_a2() { //! // This will not run in parallel to function_a1 //! } //! //! #[nonparallel(MUT_B)] //! fn function_b() { //! // This may run in parallel to function_a* //! } //! ``` extern crate proc_macro; use proc_macro::TokenStream; use quote::{quote, ToTokens}; use syn::parse::{Parse, ParseStream}; use syn::{parse, parse_macro_input, Ident, Stmt, ItemFn}; #[derive(Debug)] struct Nonparallel { ident: Ident, } impl Parse for Nonparallel { fn parse(input: ParseStream) -> Result<Self, syn::Error> { let ident = input.parse::<Ident>()?; Ok(Nonparallel { ident }) } } #[proc_macro_attribute] pub fn nonparallel(attr: TokenStream, item: TokenStream) -> TokenStream { // Parse macro attributes let Nonparallel { ident } = parse_macro_input!(attr); // Parse function let mut function: ItemFn = parse(item).expect("Could not parse ItemFn"); // Insert locking code let quoted = quote! { let guard = #ident.lock().expect("Could not lock mutex"); }; let stmt: Stmt = parse(quoted.into()).expect("Could not parse quoted statement"); function.block.stmts.insert(0, stmt); // Generate token stream TokenStream::from(function.to_token_stream()) }