Add axum_extra::extract::Form (#1031)

* Add `axum_extra::extra::Form`

* update tokio-util ban

axum-extra/src/extract/form.rs

@@ -0,0 +1,136 @@
+use axum::{
+    async_trait,
+    body::HttpBody,
+    extract::{
+        rejection::{FailedToDeserializeQueryString, FormRejection, InvalidFormContentType},
+        FromRequest, RequestParts,
+    },
+    BoxError,
+};
+use bytes::Bytes;
+use http::{header, Method};
+use serde::de::DeserializeOwned;
+use std::ops::Deref;
+
+/// Extractor that deserializes `application/x-www-form-urlencoded` requests
+/// into some type.
+///
+/// `T` is expected to implement [`serde::Deserialize`].
+///
+/// # Differences from `axum::extract::Form`
+///
+/// This extractor uses [`serde_html_form`] under-the-hood which supports multi-value items. These
+/// are sent by multiple `<input>` attributes of the same name (e.g. checkboxes) and `<select>`s
+/// with the `multiple` attribute. Those values can be collected into a `Vec` or other sequential
+/// container.
+///
+/// # Example
+///
+/// ```rust,no_run
+/// use axum_extra::extract::Form;
+/// use serde::Deserialize;
+///
+/// #[derive(Deserialize)]
+/// struct Payload {
+///     #[serde(rename = "value")]
+///     values: Vec<String>,
+/// }
+///
+/// async fn accept_form(Form(payload): Form<Payload>) {
+///     // ...
+/// }
+/// ```
+///
+/// [`serde_html_form`]: https://crates.io/crates/serde_html_form
+#[derive(Debug, Clone, Copy, Default)]
+pub struct Form<T>(pub T);
+
+impl<T> Deref for Form<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+#[async_trait]
+impl<T, B> FromRequest<B> for Form<T>
+where
+    T: DeserializeOwned,
+    B: HttpBody + Send,
+    B::Data: Send,
+    B::Error: Into<BoxError>,
+{
+    type Rejection = FormRejection;
+
+    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
+        if req.method() == Method::GET {
+            let query = req.uri().query().unwrap_or_default();
+            let value = serde_html_form::from_str(query)
+                .map_err(FailedToDeserializeQueryString::__private_new::<T, _>)?;
+            Ok(Form(value))
+        } else {
+            if !has_content_type(req, &mime::APPLICATION_WWW_FORM_URLENCODED) {
+                return Err(InvalidFormContentType::default().into());
+            }
+
+            let bytes = Bytes::from_request(req).await?;
+            let value = serde_html_form::from_bytes(&bytes)
+                .map_err(FailedToDeserializeQueryString::__private_new::<T, _>)?;
+
+            Ok(Form(value))
+        }
+    }
+}
+
+// this is duplicated in `axum/src/extract/mod.rs`
+fn has_content_type<B>(req: &RequestParts<B>, expected_content_type: &mime::Mime) -> bool {
+    let content_type = if let Some(content_type) = req.headers().get(header::CONTENT_TYPE) {
+        content_type
+    } else {
+        return false;
+    };
+
+    let content_type = if let Ok(content_type) = content_type.to_str() {
+        content_type
+    } else {
+        return false;
+    };
+
+    content_type.starts_with(expected_content_type.as_ref())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::test_helpers::*;
+    use axum::{routing::post, Router};
+    use http::{header::CONTENT_TYPE, StatusCode};
+    use serde::Deserialize;
+
+    #[tokio::test]
+    async fn supports_multiple_values() {
+        #[derive(Deserialize)]
+        struct Data {
+            #[serde(rename = "value")]
+            values: Vec<String>,
+        }
+
+        let app = Router::new().route(
+            "/",
+            post(|Form(data): Form<Data>| async move { data.values.join(",") }),
+        );
+
+        let client = TestClient::new(app);
+
+        let res = client
+            .post("/")
+            .header(CONTENT_TYPE, "application/x-www-form-urlencoded")
+            .body("value=one&value=two")
+            .send()
+            .await;
+
+        assert_eq!(res.status(), StatusCode::OK);
+        assert_eq!(res.text().await, "one,two");
+    }
+}

axum-extra/src/extract/mod.rs

@@ -1,6 +1,10 @@
 //! Additional extractors.
 
 mod cached;
+
+#[cfg(feature = "form")]
+mod form;
+
 #[cfg(feature = "cookie")]
 pub mod cookie;
 
@@ -14,3 +18,6 @@ pub use self::cookie::PrivateCookieJar;
 
 #[cfg(feature = "cookie-signed")]
 pub use self::cookie::SignedCookieJar;
+
+#[cfg(feature = "form")]
+pub use self::form::Form;