panic if non-smtp backends are used in productions

Author: pietroalbini

src/app.rs

@@ -164,13 +164,13 @@ impl App {
             read_only_replica_database: replica_database,
             github,
             github_oauth,
-            config,
             version_id_cacher,
             downloads_counter: DownloadsCounter::new(),
-            emails: Emails::from_environment(),
+            emails: Emails::from_environment(&config),
             service_metrics: ServiceMetrics::new().expect("could not initialize service metrics"),
             instance_metrics,
             http_client,
+            config,
         }
     }
 

src/config/base.rs

@@ -12,7 +12,7 @@
 use crate::{env, uploaders::Uploader, Env, Replica};
 
 pub struct Base {
-    pub(super) env: Env,
+    pub env: Env,
     uploader: Uploader,
 }
 

src/email.rs

@@ -3,7 +3,9 @@ use std::sync::Mutex;
 
 use crate::util::errors::{server_error, AppResult};
 
+use crate::config;
 use crate::middleware::log_request::add_custom_metadata;
+use crate::Env;
 use lettre::transport::file::FileTransport;
 use lettre::transport::smtp::authentication::{Credentials, Mechanism};
 use lettre::transport::smtp::SmtpTransport;
@@ -18,7 +20,7 @@ pub struct Emails {
 impl Emails {
     /// Create a new instance detecting the backend from the environment. This will either connect
     /// to a SMTP server or store the emails on the local filesystem.
-    pub fn from_environment() -> Self {
+    pub fn from_environment(config: &config::Server) -> Self {
         let backend = match (
             dotenv::var("MAILGUN_SMTP_LOGIN"),
             dotenv::var("MAILGUN_SMTP_PASSWORD"),
@@ -34,6 +36,10 @@ impl Emails {
             },
         };
 
+        if config.base.env == Env::Production && !matches!(backend, EmailBackend::Smtp { .. }) {
+            panic!("only the smtp backend is allowed in production");
+        }
+
         Self { backend }
     }