actix_web_lab_derive/
lib.rs

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

actix_web_lab_derive/
lib.rs
