chore: apply cargo fmt to core crate

config.rs had two single-line struct variants and a let-chain that
rustfmt (edition 2024) wants expanded; db.rs test module picked up the
same treatment. Whitespace-only - no behaviour change.

Why: 'cargo fmt --check' is part of every task's definition of done,
and main was handing over slightly dirty.

Application/src/core/src/config.rs

@@ -18,9 +18,17 @@ pub enum ConfigError {
     #[error("config file not found: {0}")]
     NotFound(PathBuf),
     #[error("failed to read config file {path}: {source}")]
-    Io { path: PathBuf, #[source] source: std::io::Error },
+    Io {
+        path: PathBuf,
+        #[source]
+        source: std::io::Error,
+    },
     #[error("failed to parse config file {path}: {source}")]
-    Parse { path: PathBuf, #[source] source: toml::de::Error },
+    Parse {
+        path: PathBuf,
+        #[source]
+        source: toml::de::Error,
+    },
     #[error("invalid config: {field} — {message}")]
     Invalid { field: String, message: String },
 }
@@ -145,12 +153,13 @@ pub const DEFAULT_WEB_PORT: u16 = 8080;
 impl Config {
     /// Load from `path`, deriving the default state dir from `$HOME`.
     pub fn load(path: &Path) -> Result<Config, ConfigError> {
-        let home = std::env::var_os("HOME").map(PathBuf::from).ok_or_else(|| {
+        let home =
-            ConfigError::Invalid {
+            std::env::var_os("HOME")
-                field: "state.dir".to_string(),
+                .map(PathBuf::from)
-                message: "$HOME is unset; set [state].dir explicitly".to_string(),
+                .ok_or_else(|| ConfigError::Invalid {
-            }
+                    field: "state.dir".to_string(),
-        })?;
+                    message: "$HOME is unset; set [state].dir explicitly".to_string(),
+                })?;
         Self::load_with(path, &home)
     }
 
@@ -160,17 +169,25 @@ impl Config {
             if e.kind() == std::io::ErrorKind::NotFound {
                 ConfigError::NotFound(path.to_path_buf())
             } else {
-                ConfigError::Io { path: path.to_path_buf(), source: e }
+                ConfigError::Io {
+                    path: path.to_path_buf(),
+                    source: e,
+                }
             }
         })?;
-        let raw: RawConfig =
+        let raw: RawConfig = toml::from_str(&text).map_err(|e| ConfigError::Parse {
-            toml::from_str(&text).map_err(|e| ConfigError::Parse { path: path.to_path_buf(), source: e })?;
+            path: path.to_path_buf(),
+            source: e,
+        })?;
         Self::from_raw(raw, home)
     }
 
     fn from_raw(raw: RawConfig, home: &Path) -> Result<Config, ConfigError> {
         let state = if raw.state.dir.is_empty() {
-            home.join(".config").join("rpn").to_string_lossy().into_owned()
+            home.join(".config")
+                .join("rpn")
+                .to_string_lossy()
+                .into_owned()
         } else {
             raw.state.dir.clone()
         };
@@ -186,7 +203,10 @@ impl Config {
         Ok(Config {
             database: DatabaseConfig {
                 host: raw.database.host,
-                port: raw.database.port.as_port("database.port", DEFAULT_DATABASE_PORT)?,
+                port: raw
+                    .database
+                    .port
+                    .as_port("database.port", DEFAULT_DATABASE_PORT)?,
                 user: raw.database.user,
                 password: raw.database.password,
                 name: raw.database.name,
@@ -202,7 +222,13 @@ impl Config {
 
     /// Human-readable rendering with the password masked.
     pub fn show(&self) -> String {
-        let mask = |s: &str| if s.is_empty() { String::new() } else { "***".to_string() };
+        let mask = |s: &str| {
+            if s.is_empty() {
+                String::new()
+            } else {
+                "***".to_string()
+            }
+        };
         format!(
             "[database]\n\
              host = \"{}\"\n\
@@ -320,7 +346,10 @@ dir = "/var/backup/rpn"
         let d = tempfile::tempdir().unwrap();
         let p = d.path().join("nope.toml");
         let err = Config::load_with(&p, Path::new("/home/u")).unwrap_err();
-        assert!(matches!(err, ConfigError::NotFound(ref q) if *q == p), "{err:?}");
+        assert!(
+            matches!(err, ConfigError::NotFound(ref q) if *q == p),
+            "{err:?}"
+        );
     }
 
     #[test]
@@ -424,7 +453,10 @@ dir = \"/opt/rpn\"
         let (_d, p) = dir_with("config.toml", FULL_TOML);
         let cfg = Config::load_with(&p, Path::new("/home/u")).unwrap();
         let s = cfg.show();
-        assert!(!s.contains("hunter2"), "password leaked into show output:\n{s}");
+        assert!(
+            !s.contains("hunter2"),
+            "password leaked into show output:\n{s}"
+        );
         assert!(s.contains("***"), "{s}");
         assert!(s.contains("alice"), "user should remain visible:\n{s}");
     }
@@ -441,7 +473,8 @@ dir = \"/opt/rpn\"
 
     #[test]
     fn validate_database_requires_host_user_name() {
-        let body = "[database]\nhost = \"\"\nport = \"\"\nuser = \"u\"\npassword = \"\"\nname = \"\"\n";
+        let body =
+            "[database]\nhost = \"\"\nport = \"\"\nuser = \"u\"\npassword = \"\"\nname = \"\"\n";
         let (_d, p) = dir_with("config.toml", body);
         let cfg = Config::load_with(&p, Path::new("/home/u")).unwrap();
         let err = cfg.validate_database().unwrap_err();

Application/src/core/src/db.rs

@@ -22,9 +22,16 @@ mod tests {
                 password: "pw".into(),
                 name: "rpn".into(),
             },
-            web: WebConfig { port: 8080, fqdn: String::new() },
+            web: WebConfig {
-            state: StateConfig { dir: "/tmp/rpn".into() },
+                port: 8080,
-            backup: BackupConfig { dir: "/tmp/rpn/backups".into() },
+                fqdn: String::new(),
+            },
+            state: StateConfig {
+                dir: "/tmp/rpn".into(),
+            },
+            backup: BackupConfig {
+                dir: "/tmp/rpn/backups".into(),
+            },
         }
     }
 
@@ -37,7 +44,10 @@ mod tests {
     #[test]
     fn connection_url_with_database() {
         let cfg = test_config();
-        assert_eq!(connection_url(&cfg, true), "mysql://u:***@db.example:3307/rpn");
+        assert_eq!(
+            connection_url(&cfg, true),
+            "mysql://u:***@db.example:3307/rpn"
+        );
     }
 
     #[test]
@@ -82,8 +92,19 @@ mod tests {
 
     #[test]
     fn embedded_migration_is_schema_v1() {
-        for table in ["files", "customers", "batches", "cards", "transactions", "invoices", "invoice_items"] {
+        for table in [
-            assert!(MIGRATION_V1.contains(&format!("CREATE TABLE {table}")), "{table}");
+            "files",
+            "customers",
+            "batches",
+            "cards",
+            "transactions",
+            "invoices",
+            "invoice_items",
+        ] {
+            assert!(
+                MIGRATION_V1.contains(&format!("CREATE TABLE {table}")),
+                "{table}"
+            );
         }
         // the migrations bookkeeping table is created by the app, not the file
         assert!(!MIGRATION_V1.contains("CREATE TABLE schema_migrations"));
@@ -92,11 +113,17 @@ mod tests {
     #[test]
     fn backup_command_uses_dump_client() {
         let (program, args, use_pwd) = backup_command(&test_config());
-        assert!(program == "mariadb-dump" || program == "mysqldump", "{program}");
+        assert!(
+            program == "mariadb-dump" || program == "mysqldump",
+            "{program}"
+        );
         assert!(args.iter().any(|a| a == "--host=db.example"), "{args:?}");
         assert!(args.iter().any(|a| a == "--port=3307"), "{args:?}");
         assert!(args.iter().any(|a| a == "--user=u"), "{args:?}");
-        assert!(!args.iter().any(|a| a.contains("pw")), "password on argv: {args:?}");
+        assert!(
+            !args.iter().any(|a| a.contains("pw")),
+            "password on argv: {args:?}"
+        );
         assert!(use_pwd, "MYSQL_PWD must be set for the dump client");
         assert!(args.iter().any(|a| a == "--single-transaction"), "{args:?}");
         assert!(args.iter().any(|a| a == "--databases"), "{args:?}");
@@ -113,7 +140,10 @@ mod tests {
         assert!(program == "mariadb" || program == "mysql", "{program}");
         assert!(args.iter().any(|a| a == "--host=db.example"), "{args:?}");
         assert!(args.iter().any(|a| a == "rpn"), "{args:?}");
-        assert!(!args.iter().any(|a| a.contains(".sql")), "file must not be on argv: {args:?}");
+        assert!(
+            !args.iter().any(|a| a.contains(".sql")),
+            "file must not be on argv: {args:?}"
+        );
         assert!(use_pwd);
     }