ADR-0004: Direct Contract Consumption — No Wrapper Layers

Date: 2026-07-28 Status: Implemented (Phase 4 completed 2026-07-29)

Context

During the 3-repo merge, AI-generated migration code created wrapper layers around @walnut/contract:

// apps/admin/src/const/menu.ts — wrapper layer
import { MenuType } from '@walnut/contract/menu'
export const AppConstMenuType = MenuType  // just renames

// apps/admin/src/const/app.ts — wrapper layer
import { Role } from '@walnut/contract/role'
export const AppConstRoles = Role  // just copies

// packages/axios/src/constant.ts — deprecated alias layer
export const BusinessCodeConst = {
  SUCCESS: WalnutAdminConstAppResponseCode.SUCCESS,
  // ... 11 more aliases
}

These layers cause:

• Every new contract constant needs updating in 2+ places
• Git blame shows wrapper maintenance, not real changes
• New developers don't know whether to import from @/const/menu or @walnut/contract/menu

Decision

Consumers import directly from @walnut/contract. Wrapper files are reduced to passthrough re-exports (for backward compatibility), and deprecated aliases are removed.

// ✅ Direct import
import { MenuType } from '@walnut/contract/menu'

// ✅ Passthrough (backward compat)
export { MenuType as AppConstMenuType } from '@walnut/contract/menu'

// ❌ Removed
export const BusinessCodeConst = { SUCCESS: WalnutAdminConstAppResponseCode.SUCCESS }

Consequences

• packages/axios/src/constant.ts reduced from 42 lines to 2 lines
• BusinessCodeConst removed — interceptor now uses WalnutAdminConstAppResponseCode directly
• apps/admin/src/const/menu.ts and app.ts are now passthrough re-exports
• Adding a new response code: change @walnut/contract only, consumers pick it up automatically