actix-multipart: Feature: Add typed multipart form extractor (#2883)

Co-authored-by: Rob Ede <robjtede@icloud.com>

Cargo.toml

@@ -5,6 +5,7 @@ members = [
     "actix-http-test",
     "actix-http",
     "actix-multipart",
+    "actix-multipart-derive",
     "actix-router",
     "actix-test",
     "actix-web-actors",
@@ -27,6 +28,7 @@ actix-files = { path = "actix-files" }
 actix-http = { path = "actix-http" }
 actix-http-test = { path = "actix-http-test" }
 actix-multipart = { path = "actix-multipart" }
+actix-multipart-derive = { path = "actix-multipart-derive" }
 actix-router = { path = "actix-router" }
 actix-test = { path = "actix-test" }
 actix-web = { path = "actix-web" }

actix-multipart-derive/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "actix-multipart-derive"
+version = "0.5.0"
+authors = ["Jacob Halsey <jacob@jhalsey.com>"]
+description = "Multipart form derive macro for Actix Web"
+keywords = ["http", "web", "framework", "async", "futures"]
+homepage = "https://actix.rs"
+repository = "https://github.com/actix/actix-web.git"
+license = "MIT OR Apache-2.0"
+edition = "2018"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+darling = "0.14"
+parse-size = "1"
+proc-macro2 = "1"
+quote = "1"
+syn = "1"
+
+[dev-dependencies]
+actix-multipart = "0.5"
+actix-web = "4"
+rustversion = "1"
+trybuild = "1"

actix-multipart-derive/LICENSE-APACHE

@@ -0,0 +1 @@
+../LICENSE-APACHE

actix-multipart-derive/LICENSE-MIT

@@ -0,0 +1 @@
+../LICENSE-MIT

actix-multipart-derive/README.md

@@ -0,0 +1,3 @@
+# actix-multipart-derive
+
+> The derive macro implementation for actix-multipart.

actix-multipart-derive/src/lib.rs

@@ -0,0 +1,315 @@
+//! Multipart form derive macro for Actix Web.
+//!
+//! See [`macro@MultipartForm`] for usage examples.
+
+#![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")]
+#![cfg_attr(docsrs, feature(doc_cfg))]
+
+use std::{collections::HashSet, convert::TryFrom as _};
+
+use darling::{FromDeriveInput, FromField, FromMeta};
+use parse_size::parse_size;
+use proc_macro::TokenStream;
+use proc_macro2::Ident;
+use quote::quote;
+use syn::{parse_macro_input, Type};
+
+#[derive(FromMeta)]
+enum DuplicateField {
+    Ignore,
+    Deny,
+    Replace,
+}
+
+impl Default for DuplicateField {
+    fn default() -> Self {
+        Self::Ignore
+    }
+}
+
+#[derive(FromDeriveInput, Default)]
+#[darling(attributes(multipart), default)]
+struct MultipartFormAttrs {
+    deny_unknown_fields: bool,
+    duplicate_field: DuplicateField,
+}
+
+#[derive(FromField, Default)]
+#[darling(attributes(multipart), default)]
+struct FieldAttrs {
+    rename: Option<String>,
+    limit: Option<String>,
+}
+
+struct ParsedField<'t> {
+    serialization_name: String,
+    rust_name: &'t Ident,
+    limit: Option<usize>,
+    ty: &'t Type,
+}
+
+/// Implements `MultipartCollect` for a struct so that it can be used with the `MultipartForm`
+/// extractor.
+///
+/// # Basic Use
+///
+/// Each field type should implement the `FieldReader` trait:
+///
+/// ```
+/// use actix_multipart::form::{tempfile::TempFile, text::Text, MultipartForm};
+///
+/// #[derive(MultipartForm)]
+/// struct ImageUpload {
+///     description: Text<String>,
+///     timestamp: Text<i64>,
+///     image: TempFile,
+/// }
+/// ```
+///
+/// # Optional and List Fields
+///
+/// You can also use `Vec<T>` and `Option<T>` provided that `T: FieldReader`.
+///
+/// A [`Vec`] field corresponds to an upload with multiple parts under the [same field
+/// name](https://www.rfc-editor.org/rfc/rfc7578#section-4.3).
+///
+/// ```
+/// use actix_multipart::form::{tempfile::TempFile, text::Text, MultipartForm};
+///
+/// #[derive(MultipartForm)]
+/// struct Form {
+///     category: Option<Text<String>>,
+///     files: Vec<TempFile>,
+/// }
+/// ```
+///
+/// # Field Renaming
+///
+/// You can use the `#[multipart(rename = "foo")]` attribute to receive a field by a different name.
+///
+/// ```
+/// use actix_multipart::form::{tempfile::TempFile, MultipartForm};
+///
+/// #[derive(MultipartForm)]
+/// struct Form {
+///     #[multipart(rename = "files[]")]
+///     files: Vec<TempFile>,
+/// }
+/// ```
+///
+/// # Field Limits
+///
+/// You can use the `#[multipart(limit = "<size>")]` attribute to set field level limits. The limit
+/// string is parsed using [parse_size].
+///
+/// Note: the form is also subject to the global limits configured using `MultipartFormConfig`.
+///
+/// ```
+/// use actix_multipart::form::{tempfile::TempFile, text::Text, MultipartForm};
+///
+/// #[derive(MultipartForm)]
+/// struct Form {
+///     #[multipart(limit = "2 KiB")]
+///     description: Text<String>,
+///
+///     #[multipart(limit = "512 MiB")]
+///     files: Vec<TempFile>,
+/// }
+/// ```
+///
+/// # Unknown Fields
+///
+/// By default fields with an unknown name are ignored. They can be rejected using the
+/// `#[multipart(deny_unknown_fields)]` attribute:
+///
+/// ```
+/// # use actix_multipart::form::MultipartForm;
+/// #[derive(MultipartForm)]
+/// #[multipart(deny_unknown_fields)]
+/// struct Form { }
+/// ```
+///
+/// # Duplicate Fields
+///
+/// The behaviour for when multiple fields with the same name are received can be changed using the
+/// `#[multipart(duplicate_field = "<behavior>")]` attribute:
+///
+/// - "ignore": (default) Extra fields are ignored. I.e., the first one is persisted.
+/// - "deny": A `MultipartError::UnsupportedField` error response is returned.
+/// - "replace": Each field is processed, but only the last one is persisted.
+///
+/// Note that `Vec` fields will ignore this option.
+///
+/// ```
+/// # use actix_multipart::form::MultipartForm;
+/// #[derive(MultipartForm)]
+/// #[multipart(duplicate_field = "deny")]
+/// struct Form { }
+/// ```
+///
+/// [parse_size]: https://docs.rs/parse-size/1/parse_size
+#[proc_macro_derive(MultipartForm, attributes(multipart))]
+pub fn impl_multipart_form(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input: syn::DeriveInput = parse_macro_input!(input);
+
+    let name = &input.ident;
+
+    let data_struct = match &input.data {
+        syn::Data::Struct(data_struct) => data_struct,
+        _ => {
+            return compile_err(syn::Error::new(
+                input.ident.span(),
+                "`MultipartForm` can only be derived for structs",
+            ))
+        }
+    };
+
+    let fields = match &data_struct.fields {
+        syn::Fields::Named(fields_named) => fields_named,
+        _ => {
+            return compile_err(syn::Error::new(
+                input.ident.span(),
+                "`MultipartForm` can only be derived for a struct with named fields",
+            ))
+        }
+    };
+
+    let attrs = match MultipartFormAttrs::from_derive_input(&input) {
+        Ok(attrs) => attrs,
+        Err(err) => return err.write_errors().into(),
+    };
+
+    // Parse the field attributes
+    let parsed = match fields
+        .named
+        .iter()
+        .map(|field| {
+            let rust_name = field.ident.as_ref().unwrap();
+            let attrs = FieldAttrs::from_field(field).map_err(|err| err.write_errors())?;
+            let serialization_name = attrs.rename.unwrap_or_else(|| rust_name.to_string());
+
+            let limit = match attrs.limit.map(|limit| match parse_size(&limit) {
+                Ok(size) => Ok(usize::try_from(size).unwrap()),
+                Err(err) => Err(syn::Error::new(
+                    field.ident.as_ref().unwrap().span(),
+                    format!("Could not parse size limit `{}`: {}", limit, err),
+                )),
+            }) {
+                Some(Err(err)) => return Err(compile_err(err)),
+                limit => limit.map(Result::unwrap),
+            };
+
+            Ok(ParsedField {
+                serialization_name,
+                rust_name,
+                limit,
+                ty: &field.ty,
+            })
+        })
+        .collect::<Result<Vec<_>, TokenStream>>()
+    {
+        Ok(attrs) => attrs,
+        Err(err) => return err,
+    };
+
+    // Check that field names are unique
+    let mut set = HashSet::new();
+    for field in &parsed {
+        if !set.insert(field.serialization_name.clone()) {
+            return compile_err(syn::Error::new(
+                field.rust_name.span(),
+                format!("Multiple fields named: `{}`", field.serialization_name),
+            ));
+        }
+    }
+
+    // Return value when a field name is not supported by the form
+    let unknown_field_result = if attrs.deny_unknown_fields {
+        quote!(::std::result::Result::Err(
+            ::actix_multipart::MultipartError::UnsupportedField(field.name().to_string())
+        ))
+    } else {
+        quote!(::std::result::Result::Ok(()))
+    };
+
+    // Value for duplicate action
+    let duplicate_field = match attrs.duplicate_field {
+        DuplicateField::Ignore => quote!(::actix_multipart::form::DuplicateField::Ignore),
+        DuplicateField::Deny => quote!(::actix_multipart::form::DuplicateField::Deny),
+        DuplicateField::Replace => quote!(::actix_multipart::form::DuplicateField::Replace),
+    };
+
+    // limit() implementation
+    let mut limit_impl = quote!();
+    for field in &parsed {
+        let name = &field.serialization_name;
+        if let Some(value) = field.limit {
+            limit_impl.extend(quote!(
+                #name => ::std::option::Option::Some(#value),
+            ));
+        }
+    }
+
+    // handle_field() implementation
+    let mut handle_field_impl = quote!();
+    for field in &parsed {
+        let name = &field.serialization_name;
+        let ty = &field.ty;
+
+        handle_field_impl.extend(quote!(
+            #name => ::std::boxed::Box::pin(
+                <#ty as ::actix_multipart::form::FieldGroupReader>::handle_field(req, field, limits, state, #duplicate_field)
+            ),
+        ));
+    }
+
+    // from_state() implementation
+    let mut from_state_impl = quote!();
+    for field in &parsed {
+        let name = &field.serialization_name;
+        let rust_name = &field.rust_name;
+        let ty = &field.ty;
+        from_state_impl.extend(quote!(
+            #rust_name: <#ty as ::actix_multipart::form::FieldGroupReader>::from_state(#name, &mut state)?,
+        ));
+    }
+
+    let gen = quote! {
+        impl ::actix_multipart::form::MultipartCollect for #name {
+            fn limit(field_name: &str) -> ::std::option::Option<usize> {
+                match field_name {
+                    #limit_impl
+                    _ => None,
+                }
+            }
+
+            fn handle_field<'t>(
+                req: &'t ::actix_web::HttpRequest,
+                field: ::actix_multipart::Field,
+                limits: &'t mut ::actix_multipart::form::Limits,
+                state: &'t mut ::actix_multipart::form::State,
+            ) -> ::std::pin::Pin<::std::boxed::Box<dyn ::std::future::Future<Output = ::std::result::Result<(), ::actix_multipart::MultipartError>> + 't>> {
+                match field.name() {
+                    #handle_field_impl
+                    _ => return ::std::boxed::Box::pin(::std::future::ready(#unknown_field_result)),
+                }
+            }
+
+            fn from_state(mut state: ::actix_multipart::form::State) -> ::std::result::Result<Self, ::actix_multipart::MultipartError> {
+                Ok(Self {
+                    #from_state_impl
+                })
+            }
+
+        }
+    };
+    gen.into()
+}
+
+/// Transform a syn error into a token stream for returning.
+fn compile_err(err: syn::Error) -> TokenStream {
+    TokenStream::from(err.to_compile_error())
+}

actix-multipart-derive/tests/trybuild.rs

@@ -0,0 +1,16 @@
+#[rustversion::stable(1.59)] // MSRV
+#[test]
+fn compile_macros() {
+    let t = trybuild::TestCases::new();
+
+    t.pass("tests/trybuild/all-required.rs");
+    t.pass("tests/trybuild/optional-and-list.rs");
+    t.pass("tests/trybuild/rename.rs");
+    t.pass("tests/trybuild/deny-unknown.rs");
+
+    t.pass("tests/trybuild/deny-duplicates.rs");
+    t.compile_fail("tests/trybuild/deny-parse-fail.rs");
+
+    t.pass("tests/trybuild/size-limits.rs");
+    t.compile_fail("tests/trybuild/size-limit-parse-fail.rs");
+}