Use anyhow.

Cargo.lock

@@ -2670,6 +2670,7 @@ dependencies = [
  "actix-rt",
  "actix-service",
  "actix-web",
+ "anyhow",
  "chrono",
  "claim",
  "config",

Cargo.toml

@@ -35,6 +35,7 @@ validator = "0.12.0"
 rand = { version = "0.8", features=["std_rng"] }
 sha2 = { version = "0.9" }
 tracing-actix-web = "0.4.0-beta.4"
+anyhow = "1.0.40"
 
 [dev-dependencies]
 once_cell = "1.7.2"

src/routes/subscriptions.rs

@@ -3,6 +3,7 @@ use crate::email_client::EmailClient;
 use crate::startup::ApplicationBaseUrl;
 use actix_web::http::StatusCode;
 use actix_web::{web, HttpResponse, ResponseError};
+use anyhow::Context;
 use chrono::Utc;
 use rand::distributions::Alphanumeric;
 use rand::{thread_rng, Rng};
@@ -30,16 +31,8 @@ impl TryInto<NewSubscriber> for FormData {
 pub enum SubscribeError {
     #[error("{0}")]
     ValidationError(String),
-    #[error("Failed to acquire a Postgres connection from the pool")]
-    PoolError(#[source] sqlx::Error),
-    #[error("Failed to insert new subscriber in the database.")]
-    InsertSubscriberError(#[source] sqlx::Error),
-    #[error("Failed to store the confirmation token for a new subscriber.")]
-    StoreTokenError(#[from] StoreTokenError),
-    #[error("Failed to commit SQL transaction to store a new subscriber.")]
-    TransactionCommitError(#[source] sqlx::Error),
-    #[error("Failed to send a confirmation email.")]
-    SendEmailError(#[from] reqwest::Error),
+    #[error(transparent)]
+    UnexpectedError(#[from] anyhow::Error),
 }
 
 impl std::fmt::Debug for SubscribeError {
@@ -52,11 +45,7 @@ impl ResponseError for SubscribeError {
     fn status_code(&self) -> StatusCode {
         match self {
             SubscribeError::ValidationError(_) => StatusCode::BAD_REQUEST,
-            SubscribeError::PoolError(_)
-            | SubscribeError::TransactionCommitError(_)
-            | SubscribeError::InsertSubscriberError(_)
-            | SubscribeError::StoreTokenError(_)
-            | SubscribeError::SendEmailError(_) => StatusCode::INTERNAL_SERVER_ERROR,
+            SubscribeError::UnexpectedError(_) => StatusCode::INTERNAL_SERVER_ERROR,
         }
     }
 }
@@ -76,23 +65,29 @@ pub async fn subscribe(
     base_url: web::Data<ApplicationBaseUrl>,
 ) -> Result<HttpResponse, SubscribeError> {
     let new_subscriber = form.0.try_into().map_err(SubscribeError::ValidationError)?;
-    let mut transaction = pool.begin().await.map_err(SubscribeError::PoolError)?;
+    let mut transaction = pool
+        .begin()
+        .await
+        .context("Failed to acquire a Postgres connection from the pool")?;
     let subscriber_id = insert_subscriber(&mut transaction, &new_subscriber)
         .await
-        .map_err(SubscribeError::InsertSubscriberError)?;
+        .context("Failed to insert new subscriber in the database.")?;
     let subscription_token = generate_subscription_token();
-    store_token(&mut transaction, subscriber_id, &subscription_token).await?;
+    store_token(&mut transaction, subscriber_id, &subscription_token)
+        .await
+        .context("Failed to store the confirmation token for a new subscriber.")?;
     transaction
         .commit()
         .await
-        .map_err(SubscribeError::TransactionCommitError)?;
+        .context("Failed to commit SQL transaction to store a new subscriber.")?;
     send_confirmation_email(
         &email_client,
         new_subscriber,
         &base_url.0,
         &subscription_token,
     )
-    .await?;
+    .await
+    .context("Failed to send a confirmation email.")?;
     Ok(HttpResponse::Ok().finish())
 }