actix_web_lab_derive/
lib.rs

1//! Experimental macros for Actix Web.
2
3#![forbid(unsafe_code)]
4#![cfg_attr(docsrs, feature(doc_auto_cfg))]
5
6use quote::{format_ident, quote};
7use syn::{DeriveInput, Ident, parse_macro_input, punctuated::Punctuated, token::Comma};
8
9/// Derive a `FromRequest` implementation for an aggregate struct extractor.
10///
11/// All fields of the struct need to implement `FromRequest` unless they are marked with annotations
12/// that declare different handling is required.
13///
14/// # Examples
15/// ```
16/// use actix_web::{Responder, get, http, web};
17/// use actix_web_lab::FromRequest;
18///
19/// #[derive(Debug, FromRequest)]
20/// struct RequestParts {
21///     // the FromRequest impl is used for these fields
22///     method: http::Method,
23///     pool: web::Data<u32>,
24///     req_body: String,
25///
26///     // equivalent to `req.app_data::<u64>().copied()`
27///     #[from_request(copy_from_app_data)]
28///     int: u64,
29/// }
30///
31/// #[get("/")]
32/// async fn handler(parts: RequestParts) -> impl Responder {
33///     // ...
34///     # ""
35/// }
36/// ```
37#[proc_macro_derive(FromRequest, attributes(from_request))]
38pub fn derive_from_request(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
39    let input = parse_macro_input!(input as DeriveInput);
40
41    let name = input.ident;
42
43    let data = match input.data {
44        syn::Data::Struct(data) => data,
45        syn::Data::Enum(_) | syn::Data::Union(_) => {
46            return quote! {
47                compile_error!("Deriving FromRequest is only supported on structs for now.");
48            }
49            .into();
50        }
51    };
52
53    let fields = match data.fields {
54        syn::Fields::Named(fields) => fields.named,
55        syn::Fields::Unnamed(_) | syn::Fields::Unit => {
56            return quote! {
57                compile_error!("Deriving FromRequest is only supported on structs with named fields for now.");
58            }
59            .into();
60        }
61    };
62
63    let field_names_joined = fields
64        .iter()
65        .map(|f| f.ident.clone().unwrap())
66        .collect::<Punctuated<_, Comma>>();
67
68    // i.e., field has no special handling, it's just extracted using its FromRequest impl
69    let fut_fields = fields.iter().filter(|field| {
70        field.attrs.is_empty()
71            || field
72                .attrs
73                .iter()
74                .any(|attr| attr.parse_args::<Ident>().is_err())
75    });
76
77    let field_fut_names_joined = fut_fields
78        .clone()
79        .map(|f| format_ident!("{}_fut", f.ident.clone().unwrap()))
80        .collect::<Punctuated<_, Comma>>();
81
82    let field_post_fut_names_joined = fut_fields
83        .clone()
84        .map(|f| f.ident.clone().unwrap())
85        .collect::<Punctuated<_, Comma>>();
86
87    let field_futs = fut_fields.clone().map(|field| {
88        let syn::Field { ident, ty, .. } = field;
89
90        let varname = format_ident!("{}_fut", ident.clone().unwrap());
91
92        quote! {
93            let #varname = <#ty>::from_request(&req, pl).map_err(Into::into);
94        }
95    });
96
97    let fields_copied_from_app_data = fields
98        .iter()
99        .filter(|field| {
100            field.attrs.iter().any(|attr| {
101                attr.parse_args::<Ident>().is_ok_and(|ident| ident == "copy_from_app_data")
102            })
103        })
104        .map(|field| {
105            let syn::Field { ident, ty, .. } = field;
106
107            let varname = ident.clone().unwrap();
108
109            quote! {
110                let #varname = if let Some(st) = req.app_data::<#ty>().copied() {
111                    st
112                } else {
113                    ::actix_web_lab::__reexports::tracing::debug!(
114                        "Failed to extract `{}` for `{}` handler. For this extractor to work \
115                        correctly, pass the data to `App::app_data()`. Ensure that types align in \
116                        both the set and retrieve calls.",
117                        ::std::any::type_name::<#ty>(),
118                        req.match_name().unwrap_or_else(|| req.path())
119                    );
120
121                    return ::std::boxed::Box::pin(async move {
122                        ::std::result::Result::Err(
123                            ::actix_web_lab::__reexports::actix_web::error::ErrorInternalServerError(
124                            "Requested application data is not configured correctly. \
125                            View/enable debug logs for more details.",
126                        ))
127                    })
128                };
129            }
130        });
131
132    let output = quote! {
133        impl ::actix_web::FromRequest for #name {
134            type Error = ::actix_web::Error;
135            type Future = ::std::pin::Pin<::std::boxed::Box<
136                dyn ::std::future::Future<Output = ::std::result::Result<Self, Self::Error>>
137            >>;
138
139            fn from_request(req: &::actix_web::HttpRequest, pl: &mut ::actix_web::dev::Payload) -> Self::Future {
140                use ::actix_web_lab::__reexports::actix_web::FromRequest as _;
141                use ::actix_web_lab::__reexports::futures_util::{FutureExt as _, TryFutureExt as _};
142                use ::actix_web_lab::__reexports::tokio::try_join;
143
144                #(#fields_copied_from_app_data)*
145
146                #(#field_futs)*
147
148                ::std::boxed::Box::pin(
149                    async move { try_join!( #field_fut_names_joined ) }
150                        .map_ok(move |( #field_post_fut_names_joined )| Self { #field_names_joined })
151                )
152           }
153        }
154    };
155
156    proc_macro::TokenStream::from(output)
157}
actix_web_lab_derive/lib.rs

actix_web_lab_derive/
lib.rs
