From 985e0152ff5717681f125a5c5613f9a3dd5108a0 Mon Sep 17 00:00:00 2001
From: Jonas Platte <jplatte+git@posteo.de>
Date: Tue, 17 May 2022 18:57:37 +0200
Subject: [PATCH 1/2] Add `axum_extra::extract::Query`

---
 axum-extra/Cargo.toml           |   1 +
 axum-extra/src/extract/mod.rs   |   6 ++
 axum-extra/src/extract/query.rs | 117 ++++++++++++++++++++++++++++++++
 3 files changed, 124 insertions(+)
 create mode 100644 axum-extra/src/extract/query.rs

diff --git a/axum-extra/Cargo.toml b/axum-extra/Cargo.toml
index 3e9807d14e..36df3126f3 100644
--- a/axum-extra/Cargo.toml
+++ b/axum-extra/Cargo.toml
@@ -18,6 +18,7 @@ cookie = ["cookie-lib"]
 cookie-signed = ["cookie", "cookie-lib/signed"]
 cookie-private = ["cookie", "cookie-lib/private"]
 form = ["serde", "serde_html_form"]
+query = ["serde", "serde_html_form"]
 spa = ["tower-http/fs"]
 
 [dependencies]
diff --git a/axum-extra/src/extract/mod.rs b/axum-extra/src/extract/mod.rs
index 4a98c7163c..9abed09f88 100644
--- a/axum-extra/src/extract/mod.rs
+++ b/axum-extra/src/extract/mod.rs
@@ -8,6 +8,9 @@ mod form;
 #[cfg(feature = "cookie")]
 pub mod cookie;
 
+#[cfg(feature = "query")]
+mod query;
+
 pub use self::cached::Cached;
 
 #[cfg(feature = "cookie")]
@@ -21,3 +24,6 @@ pub use self::cookie::SignedCookieJar;
 
 #[cfg(feature = "form")]
 pub use self::form::Form;
+
+#[cfg(feature = "query")]
+pub use self::query::Query;
diff --git a/axum-extra/src/extract/query.rs b/axum-extra/src/extract/query.rs
new file mode 100644
index 0000000000..dcbcdb31fd
--- /dev/null
+++ b/axum-extra/src/extract/query.rs
@@ -0,0 +1,117 @@
+use axum::{
+    async_trait,
+    extract::{
+        rejection::{FailedToDeserializeQueryString, QueryRejection},
+        FromRequest, RequestParts,
+    },
+};
+use serde::de::DeserializeOwned;
+use std::ops::Deref;
+
+/// Extractor that deserializes query strings 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::{routing::get, Router};
+/// use axum_extra::extract::Query;
+/// use serde::Deserialize;
+///
+/// #[derive(Deserialize)]
+/// struct Pagination {
+///     page: usize,
+///     per_page: usize,
+/// }
+///
+/// // This will parse query strings like `?page=2&per_page=30` into `Pagination`
+/// // structs.
+/// async fn list_things(pagination: Query<Pagination>) {
+///     let pagination: Pagination = pagination.0;
+///
+///     // ...
+/// }
+///
+/// let app = Router::new().route("/list_things", get(list_things));
+/// # async {
+/// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
+/// # };
+/// ```
+///
+/// If the query string cannot be parsed it will reject the request with a `422
+/// Unprocessable Entity` response.
+///
+/// For handling values being empty vs missing see the (query-params-with-empty-strings)[example]
+/// example.
+///
+/// [example]: https://github.com/tokio-rs/axum/blob/main/examples/query-params-with-empty-strings/src/main.rs
+#[cfg_attr(docsrs, doc(cfg(feature = "query")))]
+#[derive(Debug, Clone, Copy, Default)]
+pub struct Query<T>(pub T);
+
+#[async_trait]
+impl<T, B> FromRequest<B> for Query<T>
+where
+    T: DeserializeOwned,
+    B: Send,
+{
+    type Rejection = QueryRejection;
+
+    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
+        let query = req.uri().query().unwrap_or_default();
+        let value = serde_html_form::from_str(query)
+            .map_err(FailedToDeserializeQueryString::__private_new::<T, _>)?;
+        Ok(Query(value))
+    }
+}
+
+impl<T> Deref for Query<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+#[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(|Query(data): Query<Data>| async move { data.values.join(",") }),
+        );
+
+        let client = TestClient::new(app);
+
+        let res = client
+            .post("/?value=one&value=two")
+            .header(CONTENT_TYPE, "application/x-www-form-urlencoded")
+            .body("")
+            .send()
+            .await;
+
+        assert_eq!(res.status(), StatusCode::OK);
+        assert_eq!(res.text().await, "one,two");
+    }
+}

From 4f4906593c1fa3e18bd67f13cf182bb9eb9fcf5e Mon Sep 17 00:00:00 2001
From: Jonas Platte <jplatte+git@posteo.de>
Date: Tue, 17 May 2022 19:04:01 +0200
Subject: [PATCH 2/2] Add changelog entry for axum_extra::extract::Query

---
 axum-extra/CHANGELOG.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/axum-extra/CHANGELOG.md b/axum-extra/CHANGELOG.md
index 37d81f0bb0..ec02bd2831 100644
--- a/axum-extra/CHANGELOG.md
+++ b/axum-extra/CHANGELOG.md
@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning].
 
 # Unreleased
 
-- None.
+- **added:** Add `extract::Query` which supports multi-value items ([#1041])
+
+[#1041]: https://github.com/tokio-rs/axum/pull/1041
 
 # 0.3.2 (15. May, 2022)