From 2f64064650c02d447f5a05fcf9259a691d619236 Mon Sep 17 00:00:00 2001
From: David Pedersen <david.pdrsn@gmail.com>
Date: Fri, 17 Jun 2022 20:23:57 +0200
Subject: [PATCH] Implement `IntoResponse` for `Form` (#1095)

---
 axum/CHANGELOG.md              |  2 +
 axum/src/extract/mod.rs        |  7 +---
 axum/src/{extract => }/form.rs | 67 ++++++++++++++++++++++++----------
 axum/src/lib.rs                |  6 +++
 axum/src/response/mod.rs       |  4 ++
 5 files changed, 61 insertions(+), 25 deletions(-)
 rename axum/src/{extract => }/form.rs (78%)

diff --git a/axum/CHANGELOG.md b/axum/CHANGELOG.md
index 2568c29c0a..b6e9b7e741 100644
--- a/axum/CHANGELOG.md
+++ b/axum/CHANGELOG.md
@@ -9,9 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - **added:** Support resolving host name via `Forwarded` header in `Host`
   extractor ([#1078])
+- **added:** Implement `IntoResponse` for `Form` ([#1095])
 - **change:** axum's MSRV is now 1.56 ([#1098])
 
 [#1078]: https://github.com/tokio-rs/axum/pull/1078
+[#1095]: https://github.com/tokio-rs/axum/pull/1095
 [#1098]: https://github.com/tokio-rs/axum/pull/1098
 
 # 0.5.7 (08. June, 2022)
diff --git a/axum/src/extract/mod.rs b/axum/src/extract/mod.rs
index 6e17d973ab..41a255116a 100644
--- a/axum/src/extract/mod.rs
+++ b/axum/src/extract/mod.rs
@@ -39,11 +39,8 @@ pub use crate::Json;
 pub use crate::Extension;
 
 #[cfg(feature = "form")]
-mod form;
-
-#[cfg(feature = "form")]
-#[doc(inline)]
-pub use self::form::Form;
+#[doc(no_inline)]
+pub use crate::form::Form;
 
 #[cfg(feature = "matched-path")]
 mod matched_path;
diff --git a/axum/src/extract/form.rs b/axum/src/form.rs
similarity index 78%
rename from axum/src/extract/form.rs
rename to axum/src/form.rs
index 4f0295afd0..9974a46036 100644
--- a/axum/src/extract/form.rs
+++ b/axum/src/form.rs
@@ -1,24 +1,23 @@
-use super::{has_content_type, rejection::*, FromRequest, RequestParts};
 use crate::body::{Bytes, HttpBody};
+use crate::extract::{has_content_type, rejection::*, FromRequest, RequestParts};
 use crate::BoxError;
 use async_trait::async_trait;
-use http::Method;
+use axum_core::response::{IntoResponse, Response};
+use http::header::CONTENT_TYPE;
+use http::{Method, StatusCode};
 use serde::de::DeserializeOwned;
+use serde::Serialize;
 use std::ops::Deref;
 
-/// Extractor that deserializes `application/x-www-form-urlencoded` requests
-/// into some type.
+/// URL encoded extractor and response.
 ///
-/// `T` is expected to implement [`serde::Deserialize`].
+/// # As extractor
 ///
-/// # Example
+/// If used as an extractor `Form` will deserialize `application/x-www-form-urlencoded` request
+/// bodies into some target type via [`serde::Deserialize`].
 ///
-/// ```rust,no_run
-/// use axum::{
-///     extract::Form,
-///     routing::post,
-///     Router,
-/// };
+/// ```rust
+/// use axum::Form;
 /// use serde::Deserialize;
 ///
 /// #[derive(Deserialize)]
@@ -27,19 +26,31 @@ use std::ops::Deref;
 ///     password: String,
 /// }
 ///
-/// async fn accept_form(form: Form<SignUp>) {
-///     let sign_up: SignUp = form.0;
-///
+/// async fn accept_form(Form(sign_up): Form<SignUp>) {
 ///     // ...
 /// }
+/// ```
+///
+/// Note that `Content-Type: multipart/form-data` requests are not supported. Use [`Multipart`]
+/// instead.
+///
+/// # As response
+///
+/// ```rust
+/// use axum::Form;
+/// use serde::Serialize;
+///
+/// #[derive(Serialize)]
+/// struct Payload {
+///     value: String,
+/// }
 ///
-/// let app = Router::new().route("/sign_up", post(accept_form));
-/// # async {
-/// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
-/// # };
+/// async fn handler() -> Form<Payload> {
+///     Form(Payload { value: "foo".to_owned() })
+/// }
 /// ```
 ///
-/// Note that `Content-Type: multipart/form-data` requests are not supported.
+/// [`Multipart`]: crate::extract::Multipart
 #[cfg_attr(docsrs, doc(cfg(feature = "form")))]
 #[derive(Debug, Clone, Copy, Default)]
 pub struct Form<T>(pub T);
@@ -74,6 +85,22 @@ where
     }
 }
 
+impl<T> IntoResponse for Form<T>
+where
+    T: Serialize,
+{
+    fn into_response(self) -> Response {
+        match serde_urlencoded::to_string(&self.0) {
+            Ok(body) => (
+                [(CONTENT_TYPE, mime::APPLICATION_WWW_FORM_URLENCODED.as_ref())],
+                body,
+            )
+                .into_response(),
+            Err(err) => (StatusCode::INTERNAL_SERVER_ERROR, err.to_string()).into_response(),
+        }
+    }
+}
+
 impl<T> Deref for Form<T> {
     type Target = T;
 
diff --git a/axum/src/lib.rs b/axum/src/lib.rs
index ac977976ef..7fbf51c267 100644
--- a/axum/src/lib.rs
+++ b/axum/src/lib.rs
@@ -395,6 +395,8 @@
 pub(crate) mod macros;
 
 mod extension;
+#[cfg(feature = "form")]
+mod form;
 #[cfg(feature = "json")]
 mod json;
 #[cfg(feature = "headers")]
@@ -434,5 +436,9 @@ pub use self::routing::Router;
 #[cfg(feature = "headers")]
 pub use self::typed_header::TypedHeader;
 
+#[doc(inline)]
+#[cfg(feature = "headers")]
+pub use form::Form;
+
 #[doc(inline)]
 pub use axum_core::{BoxError, Error};
diff --git a/axum/src/response/mod.rs b/axum/src/response/mod.rs
index 50c2c458c4..695b931c22 100644
--- a/axum/src/response/mod.rs
+++ b/axum/src/response/mod.rs
@@ -15,6 +15,10 @@ pub use crate::Json;
 #[cfg(feature = "headers")]
 pub use crate::TypedHeader;
 
+#[cfg(feature = "form")]
+#[doc(no_inline)]
+pub use crate::form::Form;
+
 #[doc(no_inline)]
 pub use crate::Extension;