fix(config): default split DB ports by backend

When using the split `[database]` fields instead of a full
`connection_url`, `port` was previously required in both `validate()`
and `database_url()`. Make it optional and fall back to the backend's
well-known default via a new `DatabaseBackend::default_port()` (3306
for MySQL, 5432 for PostgreSQL). Callers that already set `port`
explicitly continue to win.

Also:
- drop `port` from the two user-facing error messages
  (`Error::ConfigValidation` in `Config::validate` and
  `Error::InvalidDatabaseConfig` as the defensive fallthrough in
  `Config::database_url`) so they match the new required-field set;
- exit with status 1 (instead of a silent `return`) when `App::new`
  or `App::serve` fails, so init failures are visible to systemd and
  other supervisors rather than looking like a clean shutdown;
- document the port default in the example `config.toml` comment;
- add MySQL and PostgreSQL port-omission regression tests.

Signed-off-by: JmPotato <github@ipotato.me>

Author: JmPotato

config.toml

@@ -38,7 +38,8 @@ backend = "mysql"
 # connection_url = "postgres://postgres:password@127.0.0.1:5432/rsomhaP"
 #
 # If you use the split fields below instead of `connection_url`, `backend`
-# controls whether `mysql://` or `postgres://` is generated.
+# controls whether `mysql://` or `postgres://` is generated. `port` is
+# optional; it defaults to 3306 for MySQL and 5432 for PostgreSQL.
 username = "root"
 password = "password"
 host = "127.0.0.1"

src/config.rs

@@ -49,6 +49,13 @@ impl DatabaseBackend {
             Self::Postgres => "postgres",
         }
     }
+
+    fn default_port(self) -> u16 {
+        match self {
+            Self::MySql => 3306,
+            Self::Postgres => 5432,
+        }
+    }
 }
 
 #[derive(Clone, Debug, Deserialize)]
@@ -207,11 +214,10 @@ impl Config {
             && (self.database.username.is_none()
                 || self.database.password.is_none()
                 || self.database.host.is_none()
-                || self.database.port.is_none()
                 || self.database.database.is_none())
         {
             return Err(Error::ConfigValidation(
-                "invalid database config, please specify the connection URL or the username, password, host, port and database".to_string(),
+                "invalid database config, please specify the connection URL or the username, password, host and database".to_string(),
             ));
         }
 
@@ -244,7 +250,9 @@ impl Config {
                     .host
                     .as_ref()
                     .ok_or(Error::InvalidDatabaseConfig)?,
-                self.database.port.ok_or(Error::InvalidDatabaseConfig)?,
+                self.database
+                    .port
+                    .unwrap_or(self.database.backend.default_port()),
                 self.database
                     .database
                     .as_ref()
@@ -402,6 +410,43 @@ database = "rsomhaP"
         );
     }
 
+    #[test]
+    fn test_database_url_defaults_mysql_port_when_split_fields_omit_port() {
+        let config = parse_config(
+            r#"
+username = "root"
+password = "password"
+host = "127.0.0.1"
+database = "rsomhaP"
+"#,
+        );
+
+        config.validate().unwrap();
+        assert_eq!(
+            config.database_url().unwrap(),
+            "mysql://root:password@127.0.0.1:3306/rsomhaP"
+        );
+    }
+
+    #[test]
+    fn test_database_url_defaults_postgres_port_when_split_fields_omit_port() {
+        let config = parse_config(
+            r#"
+backend = "postgres"
+username = "postgres"
+password = "password"
+host = "127.0.0.1"
+database = "rsomhaP"
+"#,
+        );
+
+        config.validate().unwrap();
+        assert_eq!(
+            config.database_url().unwrap(),
+            "postgres://postgres:password@127.0.0.1:5432/rsomhaP"
+        );
+    }
+
     #[test]
     fn test_database_url_prefers_connection_url_over_backend_field() {
         let config = parse_config(

src/error.rs

@@ -18,7 +18,7 @@ pub enum Error {
     #[error("config validation failed: {0}")]
     ConfigValidation(String),
 
-    #[error("invalid database config, please specify the connection URL or the username, password, host, port and database")]
+    #[error("invalid database config, please specify the connection URL or the username, password, host and database")]
     InvalidDatabaseConfig,
 
     #[error("page with same title {0} already exists")]

src/main.rs

@@ -9,11 +9,11 @@ async fn main() {
         Ok(app) => app,
         Err(e) => {
             error!("failed to create app: {}", e);
-            return;
+            std::process::exit(1);
         }
     };
     if let Err(e) = app.serve().await {
         error!("failed to serve app: {}", e);
-        return;
+        std::process::exit(1);
     }
 }