#
actix_macros/
lib.rs

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    //! Macros for Actix system and runtime.
    //!
    //! The [`actix-rt`](https://docs.rs/actix-rt) crate must be available for macro output to compile.
    //!
    //! # Entry-point
    //! See docs for the [`#[main]`](macro@main) macro.
    //!
    //! # Tests
    //! See docs for the [`#[test]`](macro@test) macro.

    #![deny(rust_2018_idioms, nonstandard_style)]
    #![warn(future_incompatible)]
    #![doc(html_logo_url = "https://actix.rs/img/logo.png")]
    #![doc(html_favicon_url = "https://actix.rs/favicon.ico")]

    use proc_macro::TokenStream;
    use quote::quote;
    use syn::parse::Parser as _;

    type AttributeArgs = syn::punctuated::Punctuated<syn::Meta, syn::Token![,]>;

    /// Marks async entry-point function to be executed by Actix system.
    ///
    /// # Examples
    /// ```
    /// #[actix_rt::main]
    /// async fn main() {
    ///     println!("Hello world");
    /// }
    /// ```
    #[proc_macro_attribute]
    pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
        let mut input = match syn::parse::<syn::ItemFn>(item.clone()) {
            Ok(input) => input,
            // on parse err, make IDEs happy; see fn docs
            Err(err) => return input_and_compile_error(item, err),
        };

        let parser = AttributeArgs::parse_terminated;
        let args = match parser.parse(args.clone()) {
            Ok(args) => args,
            Err(err) => return input_and_compile_error(args, err),
        };

        let attrs = &input.attrs;
        let vis = &input.vis;
        let sig = &mut input.sig;
        let body = &input.block;

        if sig.asyncness.is_none() {
            return syn::Error::new_spanned(
                sig.fn_token,
                "the async keyword is missing from the function declaration",
            )
            .to_compile_error()
            .into();
        }

        let mut system = syn::parse_str::<syn::Path>("::actix_rt::System").unwrap();

        for arg in &args {
            match arg {
                syn::Meta::NameValue(syn::MetaNameValue {
                    path,
                    value:
                        syn::Expr::Lit(syn::ExprLit {
                            lit: syn::Lit::Str(lit),
                            ..
                        }),
                    ..
                }) => match path
                    .get_ident()
                    .map(|i| i.to_string().to_lowercase())
                    .as_deref()
                {
                    Some("system") => match lit.parse() {
                        Ok(path) => system = path,
                        Err(_) => {
                            return syn::Error::new_spanned(lit, "Expected path")
                                .to_compile_error()
                                .into();
                        }
                    },
                    _ => {
                        return syn::Error::new_spanned(arg, "Unknown attribute specified")
                            .to_compile_error()
                            .into();
                    }
                },

                _ => {
                    return syn::Error::new_spanned(arg, "Unknown attribute specified")
                        .to_compile_error()
                        .into();
                }
            }
        }

        sig.asyncness = None;

        (quote! {
            #(#attrs)*
            #vis #sig {
                <#system>::new().block_on(async move { #body })
            }
        })
        .into()
    }

    /// Marks async test function to be executed in an Actix system.
    ///
    /// # Examples
    /// ```
    /// #[actix_rt::test]
    /// async fn my_test() {
    ///     assert!(true);
    /// }
    /// ```
    #[proc_macro_attribute]
    pub fn test(args: TokenStream, item: TokenStream) -> TokenStream {
        let mut input = match syn::parse::<syn::ItemFn>(item.clone()) {
            Ok(input) => input,
            // on parse err, make IDEs happy; see fn docs
            Err(err) => return input_and_compile_error(item, err),
        };

        let parser = AttributeArgs::parse_terminated;
        let args = match parser.parse(args.clone()) {
            Ok(args) => args,
            Err(err) => return input_and_compile_error(args, err),
        };

        let attrs = &input.attrs;
        let vis = &input.vis;
        let sig = &mut input.sig;
        let body = &input.block;
        let mut has_test_attr = false;

        for attr in attrs {
            if attr.path().is_ident("test") {
                has_test_attr = true;
            }
        }

        if sig.asyncness.is_none() {
            return syn::Error::new_spanned(
                input.sig.fn_token,
                "the async keyword is missing from the function declaration",
            )
            .to_compile_error()
            .into();
        }

        sig.asyncness = None;

        let missing_test_attr = if has_test_attr {
            quote! {}
        } else {
            quote! { #[::core::prelude::v1::test] }
        };

        let mut system = syn::parse_str::<syn::Path>("::actix_rt::System").unwrap();

        for arg in &args {
            match arg {
                syn::Meta::NameValue(syn::MetaNameValue {
                    path,
                    value:
                        syn::Expr::Lit(syn::ExprLit {
                            lit: syn::Lit::Str(lit),
                            ..
                        }),
                    ..
                }) => match path
                    .get_ident()
                    .map(|i| i.to_string().to_lowercase())
                    .as_deref()
                {
                    Some("system") => match lit.parse() {
                        Ok(path) => system = path,
                        Err(_) => {
                            return syn::Error::new_spanned(lit, "Expected path")
                                .to_compile_error()
                                .into();
                        }
                    },
                    _ => {
                        return syn::Error::new_spanned(arg, "Unknown attribute specified")
                            .to_compile_error()
                            .into();
                    }
                },
                _ => {
                    return syn::Error::new_spanned(arg, "Unknown attribute specified")
                        .to_compile_error()
                        .into();
                }
            }
        }

        (quote! {
            #missing_test_attr
            #(#attrs)*
            #vis #sig {
                <#system>::new().block_on(async { #body })
            }
        })
        .into()
    }

    /// Converts the error to a token stream and appends it to the original input.
    ///
    /// Returning the original input in addition to the error is good for IDEs which can gracefully
    /// recover and show more precise errors within the macro body.
    ///
    /// See <https://github.com/rust-analyzer/rust-analyzer/issues/10468> for more info.
    fn input_and_compile_error(mut item: TokenStream, err: syn::Error) -> TokenStream {
        let compile_err = TokenStream::from(err.to_compile_error());
        item.extend(compile_err);
        item
    }