Adding a domain field

The trap: #[serde(default)] makes old saves load, but it does nothing for SQLite. The repositories in src-tauri/crates/db/src/repositories/ use hand-written positional SQL, so a field that isn't in the column lists is silently dropped on every save/load round trip — with no error, no warning, and a passing test suite.

Do all six steps.

1. The domain type

src-tauri/crates/domain/src/ — team.rs, player.rs, staff.rs, manager.rs, league.rs, …

pub struct Team {
    // …
    #[serde(default)]
    pub youth_budget: i64,
}

Use #[serde(default = "default_youth_budget")] with a function when zero, empty, or None is the wrong value for an old save. Think about what a save written before this feature existed should look like once loaded — that is what the default has to produce.

Domain types hold data, not logic. Behaviour goes in ofm_core.

2. The repository — five edit sites

Take Team as the worked example; team_repo.rs is the reference for the rest. Open src-tauri/crates/db/src/repositories/team_repo.rs and edit all five:

1. save_team's INSERT OR REPLACE INTO teams (…) column list — add the column.

2. Its VALUES (?1, ?2, …, ?N) run — add one more placeholder. The count must match the column list exactly or the insert fails at runtime.

3. The params![…] list — add the value, in the same position as the column.

4. row_to_team's positional mapping — row.get(N)?. Appending at the end is safest; inserting in the middle shifts every index after it, and nothing will tell you if you miss one.

5. Both SELECT column lists — load_all_teams and load_team. Two separate strings that must stay in sync. For a column added by a migration, wrap it as COALESCE(youth_budget, <default>) so rows written before the migration read back as the default — the existing JSON columns (media_json, player_roles_json, …) show the pattern.

   <default> must be the same value your serde default produces. These are two independent fallbacks for the same field: serde covers a save loaded from JSON, COALESCE covers a row written before the migration. If step 1 used #[serde(default = "default_youth_budget")] returning 500_000, then COALESCE(youth_budget, 0) makes the same save load differently depending on which path it came through. Either match the two, or give the column a non-null SQL DEFAULT in the migration and drop the COALESCE.

Other repositories in that directory (player_repo.rs, staff_repo.rs, competition_repo.rs, …) follow the same five-site shape.

3. The migration

• Add src-tauri/crates/db/src/sql/vNNN_<short_description>.sql, numbered after the current highest file.
• Register it in src-tauri/crates/db/src/migrations.rs (all_migrations()).
• Bump MIGRATION_COUNT at the top of that file — the migration tests assert on it.

Migrations are append-only and must be idempotent; migrations.rs has a test that re-applies them (test_migrations_are_idempotent). Use ALTER TABLE … ADD COLUMN … DEFAULT …; never rewrite or renumber an existing migration, because shipped saves have already run it.

4. Prove it round-trips

This is the step that catches the dropped-column bug, so write it before the repository edits.

In src-tauri/crates/db/, extend the nearest existing round-trip test: build a value with the new field set to something non-default, save it, load it back, assert the field survived. A test that uses the default value passes even when the column is missing entirely.

cargo test --manifest-path src-tauri/Cargo.toml -p db
cargo test --manifest-path src-tauri/Cargo.toml --workspace

5. The rest of the backend

• Game logic for the field goes in ofm_core, not domain.
• If the field should reach the match engine, do not import domain into engine. Add the field to the engine's own mirror type and extend the conversion in ofm_core/turn/.
• If an AI agent should be able to read or set it, see /add-mcp-tool.

6. The frontend

• Add the field to the matching TypeScript type (src/store/types.ts or the relevant service types). Optional (?) if old saves may not have it.
• Any label, unit, or tooltip for it is a user-facing string → /add-ui-string, all 11 locales.

Checklist

• Field added to the domain type with #[serde(default)] or an explicit default fn
• Default value is correct for a save written before the field existed
• Repository INSERT column list updated
• VALUES (?1…?N) placeholder count updated to match
• params![…] updated, same order
• row_to_* positional row.get(N)? updated
• Both SELECT lists updated, with COALESCE for the migrated column
• sql/vNNN_*.sql added and registered in migrations.rs
• MIGRATION_COUNT bumped
• Round-trip test with a non-default value, written first
• cargo test --workspace and cargo clippy --workspace --all-targets green
• Frontend type updated; any new label translated into all 11 locales