Let API handlers return arbitrary response parts

Author: GrantGryczan

backend/api.rs

@@ -187,7 +187,31 @@ impl<T: Serialize> IntoResponse for Json<T> {
 struct Query<T>(pub T);
 
 /// An API response type.
-type Response<T> = std::result::Result<(StatusCode, Json<T>), Error>;
+trait Response<T>: IntoResponse {}
+
+/// Implements [`Response`] for types with various tuple lengths.
+macro_rules! impl_response {
+    ( $($ty:ident),* $(,)? ) => {
+        // Always require an explicit status code in `Ok` responses so the most appropriate
+        // successful status code is more likely to be considered each time.
+        impl<R, $($ty,)*> Response<R> for std::result::Result<(StatusCode, $($ty,)* Json<R>), Error>
+        where
+            std::result::Result<(StatusCode, $($ty,)* Json<R>), Error>: IntoResponse,
+        {
+        }
+    }
+}
+
+impl_response!();
+impl_response!(T1);
+impl_response!(T1, T2);
+impl_response!(T1, T2, T3);
+impl_response!(T1, T2, T3, T4);
+impl_response!(T1, T2, T3, T4, T5);
+impl_response!(T1, T2, T3, T4, T5, T6);
+impl_response!(T1, T2, T3, T4, T5, T6, T7);
+impl_response!(T1, T2, T3, T4, T5, T6, T7, T8);
+impl_response!(T1, T2, T3, T4, T5, T6, T7, T8, T9);
 
 /// Routes a request to an API endpoint.
 pub(super) async fn handle(request: Request) -> axum::response::Response {

backend/api/routes/v1/email_verification.rs

@@ -47,7 +47,7 @@ pub(crate) enum GetQuery {
 ///
 /// See [`crate::api::Error`].
 #[debug_handler]
-pub(crate) async fn get(Query(query): Query<GetQuery>) -> Response<GetResponse> {
+pub(crate) async fn get(Query(query): Query<GetQuery>) -> impl Response<GetResponse> {
     let email = match query {
         GetQuery::Token { token } => {
             let token_hash = hash_without_salt(&token);
@@ -122,7 +122,7 @@ pub(crate) struct PostRequest {
 ///
 /// See [`crate::api::Error`].
 #[debug_handler]
-pub(crate) async fn post(Json(body): Json<PostRequest>) -> Response<PostResponse> {
+pub(crate) async fn post(Json(body): Json<PostRequest>) -> impl Response<PostResponse> {
     // We don't want bots creating accounts or spamming people with verification emails.
     if !captcha::verify(&body.captcha_token).await? {
         return Err(api::Error::CaptchaFailed);

backend/api/routes/v1/email_verification/code.rs

@@ -25,7 +25,7 @@ pub(crate) struct PostQuery {
 ///
 /// See [`crate::api::Error`].
 #[debug_handler]
-pub(crate) async fn post(Query(query): Query<PostQuery>) -> Response<PostResponse> {
+pub(crate) async fn post(Query(query): Query<PostQuery>) -> impl Response<PostResponse> {
     let token_hash = hash_without_salt(&query.token);
 
     let code = generate_short_code();

backend/api/routes/v1/password_reset.rs

@@ -35,7 +35,7 @@ pub(crate) struct GetQuery {
 ///
 /// See [`crate::api::Error`].
 #[debug_handler]
-pub(crate) async fn get(Query(query): Query<GetQuery>) -> Response<GetResponse> {
+pub(crate) async fn get(Query(query): Query<GetQuery>) -> impl Response<GetResponse> {
     let token_hash = hash_without_salt(&query.token);
 
     let Some(password_reset) = db::transaction!(async |tx| -> TxResult<_, api::Error> {
@@ -87,7 +87,7 @@ pub(crate) struct PostRequest {
 ///
 /// See [`crate::api::Error`].
 #[debug_handler]
-pub(crate) async fn post(Json(body): Json<PostRequest>) -> Response<PostResponse> {
+pub(crate) async fn post(Json(body): Json<PostRequest>) -> impl Response<PostResponse> {
     // We don't want bots spamming people with password reset emails.
     if !captcha::verify(&body.captcha_token).await? {
         return Err(api::Error::CaptchaFailed);

backend/api/routes/v1/password_reset/password.rs

@@ -36,7 +36,7 @@ pub(crate) struct PostRequest {
 pub(crate) async fn post(
     Query(query): Query<PostQuery>,
     Json(body): Json<PostRequest>,
-) -> Response<PostResponse> {
+) -> impl Response<PostResponse> {
     let token_hash = hash_without_salt(&query.token);
 
     let password_hash = hash_with_salt(&body.password);

backend/api/routes/v1/sessions.rs

@@ -49,7 +49,7 @@ pub(crate) struct PostRequest {
 pub(crate) async fn post(
     cookies: Cookies,
     Json(body): Json<PostRequest>,
-) -> Response<PostResponse> {
+) -> impl Response<PostResponse> {
     let token = db::transaction!(async |tx| -> TxResult<_, api::Error> {
         let Some(user) = sqlx::query!(
             "SELECT id, password_hash FROM users

backend/api/routes/v1/users.rs

@@ -39,7 +39,7 @@ pub(crate) struct PostRequest {
 ///
 /// See [`crate::api::Error`].
 #[debug_handler]
-pub(crate) async fn post(Json(body): Json<PostRequest>) -> Response<PostResponse> {
+pub(crate) async fn post(Json(body): Json<PostRequest>) -> impl Response<PostResponse> {
     let mut user_id = NewUserId::generate();
 
     let password_hash = hash_with_salt(&body.password);