Refactor error handling for confirm handler.

src/routes/subscriptions.rs

@@ -196,7 +196,7 @@ impl std::fmt::Display for StoreTokenError {
     }
 }
 
-fn error_chain_fmt(
+pub fn error_chain_fmt(
     e: &impl std::error::Error,
     f: &mut std::fmt::Formatter<'_>,
 ) -> std::fmt::Result {

src/routes/subscriptions_confirm.rs

@@ -1,4 +1,7 @@
-use actix_web::{web, HttpResponse};
+use crate::routes::error_chain_fmt;
+use actix_web::http::StatusCode;
+use actix_web::{web, HttpResponse, ResponseError};
+use anyhow::Context;
 use sqlx::PgPool;
 use uuid::Uuid;
 
@@ -7,25 +10,43 @@ pub struct Parameters {
     subscription_token: String,
 }
 
+#[derive(thiserror::Error)]
+pub enum ConfirmationError {
+    #[error(transparent)]
+    UnexpectedError(#[from] anyhow::Error),
+    #[error("There is no subscriber associated with the provided token.")]
+    UnknownToken,
+}
+
+impl std::fmt::Debug for ConfirmationError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        error_chain_fmt(self, f)
+    }
+}
+
+impl ResponseError for ConfirmationError {
+    fn status_code(&self) -> StatusCode {
+        match self {
+            Self::UnknownToken => StatusCode::UNAUTHORIZED,
+            Self::UnexpectedError(_) => StatusCode::INTERNAL_SERVER_ERROR,
+        }
+    }
+}
+
 #[tracing::instrument(name = "Confirm a pending subscriber", skip(parameters, pool))]
 pub async fn confirm(
     parameters: web::Query<Parameters>,
     pool: web::Data<PgPool>,
-) -> Result<HttpResponse, HttpResponse> {
-    let id = get_subscriber_id_from_token(&pool, &parameters.subscription_token)
+) -> Result<HttpResponse, ConfirmationError> {
+    let subscriber_id = get_subscriber_id_from_token(&pool, &parameters.subscription_token)
         .await
-        .map_err(|_| HttpResponse::InternalServerError().finish())?;
-    match id {
-        // Non-existing token!
-        None => Err(HttpResponse::Unauthorized().finish()),
-        Some(subscriber_id) => {
+        .context("Failed to retrieve the subscriber id associated with the provided token.")?
+        .ok_or(ConfirmationError::UnknownToken)?;
     confirm_subscriber(&pool, subscriber_id)
         .await
-                .map_err(|_| HttpResponse::InternalServerError().finish())?;
+        .context("Failed to update the subscriber status to `confirmed`.")?;
     Ok(HttpResponse::Ok().finish())
 }
-    }
-}
 
 #[tracing::instrument(name = "Mark subscriber as confirmed", skip(subscriber_id, pool))]
 pub async fn confirm_subscriber(pool: &PgPool, subscriber_id: Uuid) -> Result<(), sqlx::Error> {