// When adding values to any union type in a domains/models/ file
| name | ddd-type-duplication-across-layers |
| description | When adding values to any union type in a domains/models/ file |
| version | 1.0.0 |
| source | continuous-learning |
| status | approved |
| learned_from | skills/learned/ddd-type-duplication-across-layers.md |
Extracted: 2026-02-23 Context: Angular DDD codebase (gc.webapp) where domain types are duplicated in infrastructure API models
When adding a new value to a domain union type (e.g., CalculationBase), the build breaks because the same type is hardcoded separately in the infrastructure layer (API request/response models). The domain type compiles fine, but the adapter that maps domain models to API requests fails with Type 'X' is not assignable to type 'A' | 'B' | 'C'.
After modifying a domain union type, always search the entire codebase for other occurrences of the same union values:
grep -r "'Value1'.*'Value2'.*'Value3'" src/app/<domain>/
Common locations for duplicated types in this codebase:
domains/models/ - Domain type (primary)infrastructure/api/request/ - API request typesinfrastructure/api/response/ - API response typesdomains/rules/*.spec.ts - Test files with hardcoded arrays// Domain model (updated)
export type CalculationBase = 'AmountExclTax' | 'Hectoliter' | 'Quantity' | 'Kilogram' | 'Liter';
// API request model (forgotten) - build break
export interface CreateTaxRequest {
calculationBase: 'AmountExclTax' | 'Hectoliter' | 'Quantity'; // missing new values!
}
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