Backend Add Field

Add Field to Existing Module

Not for new modules — use @backend-nest/create-module.

Reference: Find the target module in src/modules/{feature}/ and its Prisma model first.

Checklist

[ ] 1. Prisma — add field (+ relation/junction if needed) + migrate
[ ] 2. Create DTO — required/optional field decorator
[ ] 3. Update DTO — optional version of same field
[ ] 4. GetAll DTO — only if field is a list filter
[ ] 5. Service — create, update, getAll where, select/include
[ ] 6. Relations — connect/disconnect, junction cleanup on delete
[ ] 7. Search — add to where.OR if text-searchable
[ ] 8. Verify barrel export in dto/index.ts unchanged

Step 1 — Prisma

Add the field to the existing model in schema.prisma:

model product {
  // ...existing fields
  sku         String?   // new optional string
  isFeatured  Boolean   @default(false)
  typeId      Int?      // new FK
  type        type?     @relation(fields: [typeId], references: [id])
}

npx prisma migrate dev --name add-product-sku-and-featured

See @backend-nest/prisma-database for ID types, soft delete, indexes.

Step 2 — DTOs

Use global decorators — see @backend-nest/global-dtos.

Create DTO — add the new field:

export class CreateProductDto {
  // ...existing fields
  @OptionalStringField('Stock keeping unit') sku?: string;
  @OptionalBooleanField() isFeatured?: boolean;
  @OptionalNumberField() typeId?: number;
  @OptionalEnumField(ProductStatus) status?: ProductStatus;
}

Update DTO — mirror create with optional decorators:

@OptionalStringField() sku?: string;
@OptionalBooleanField() isFeatured?: boolean;
@OptionalNumberField() typeId?: number;

GetAll DTO — only when the field is a filter on list endpoints:

export class GetAllProductsDto {
  @OptionalBooleanField() isFeatured?: boolean;
  @OptionalNumberField() typeId?: number;
  @OptionalEnumField(ProductStatus) status?: ProductStatus;
}

Step 3 — Service

create

Spread scalar fields from DTO. Handle relations separately:

const created = await this.prisma.product.create({
  data: {
    ...dto,
    typeId: undefined, // strip FK before spread if using connect
    type: dto.typeId ? { connect: { id: dto.typeId } } : undefined,
  },
});

update

Build a data object — only include provided fields:

const data: Prisma.productUpdateInput = {};
if (dto.sku !== undefined) data.sku = dto.sku;
if (dto.isFeatured !== undefined) data.isFeatured = dto.isFeatured;
if (dto.typeId !== undefined) {
  data.type = dto.typeId ? { connect: { id: dto.typeId } } : { disconnect: true };
}
await this.prisma.product.update({ where: { id }, data });

getAll — filter

if (dto.isFeatured !== undefined) where.isFeatured = dto.isFeatured;
if (dto.typeId) where.typeId = dto.typeId;
if (dto.status) where.status = dto.status;

getAll / getOne — return the field

Ensure findMany/findFirst selects or includes the new field (default unless select omits it). Add relation to include if needed:

include: { type: true }

search (text fields only)

where.OR = [
  // ...existing
  { sku: { contains: search.search, mode: 'insensitive' } },
];

Step 4 — Relations

Many-to-many replace pattern:

await this.prisma.product_category.deleteMany({ where: { productId: id } });
await this.prisma.product_category.createMany({
  data: dto.categoryIds.map((categoryId) => ({ productId: id, categoryId })),
});

Add junction fields to create/update DTOs: @RequiredArrayOfNumbersField() categoryIds: number[]

Step 5 — Special field types

Step 6 — Controller

Usually no change — existing endpoints accept expanded DTOs.

Add controller/query changes only when:

• New filter on getAll → already covered by GetAll DTO
• New dedicated endpoint (rare) — e.g. bulk update of the new field

Verification

[ ] Migration applied
[ ] Create with new field works
[ ] Update with new field works (and partial update omits undefined)
[ ] List filter works (if GetAll DTO added)
[ ] Relation connect/disconnect works
[ ] Swagger reflects new DTO fields