nestjs-crud / nestjs-repository: a create body that validates to {} is rejected with a bare 400

[tnramalho]

Summary

A create whose body validates to an empty object ({}) is answered with a bare 400 Bad Request (no message), even though the body already passed the operation's input schema. Two places reject the empty object: CrudAdapter.prepareEntityBeforeSave and RepositoryAdapter.prepare.

This blocks a common shape: a resource whose every column is filled server-side (parent id from the path, owner from the actor, ids/timestamps from a hook). The client has nothing to send, so it posts {}.

Versions: @concepta/nestjs-crud@8.0.0-alpha.9, @concepta/nestjs-repository@8.0.0-alpha.9, @nestjs/common@12.0.0-alpha.6, zod@4.4.3.

Steps to reproduce

// Every column is stamped by hooks; the client sends nothing.
@Entity('stamps')
class StampEntity {
  @PrimaryGeneratedColumn('uuid') id!: string;
  @Column({ type: 'uuid' }) parentId!: string;   // from the path, via a hook
  @Column({ type: 'varchar' }) userId!: string;  // from the actor, via a hook
}

const stampCreateSchema = withOpenApi(
  z.object({ note: z.string().optional() }),
  'StampCreateDto',
);

// controller config (generated CRUD)
operations: [{ operation: Operation.Create, request: { body: stampCreateSchema } }]

POST /parents/1/stamps
Content-Type: application/json

{}

Expected

201 — the body passed the schema, so {} is a valid create; the hooks fill the row.

Actual

{ "message": "Bad Request", "statusCode": 400 }

No details, no field — the client cannot tell what was wrong (nothing was).

Where

packages/nestjs-crud/src/infrastructure/adapters/crud.adapter.ts:

prepareEntityBeforeSave(dto, context) {
  if (!isObject(dto)) return undefined;
  // …params merge…
  if (!Object.keys(merged).length) return undefined;   // <- rejects {}
  return this.repository.prepare(merged);
}

async create(context, dto) {
  const entity = this.prepareEntityBeforeSave(dto, context);
  if (!entity) throw new BadRequestException();          // <- bare 400
  …
}

packages/nestjs-repository/src/repository/repository-adapter.ts:

prepare(dto) {
  if (!isObject(dto) || !Object.keys(dto).length) return undefined; // <- rejects {} too
  …
  return Object.assign(new entityType(), dto);
}

Why it happens

Both checks predate schema validation. In alpha.9 every CRUD body goes through the input schema before the adapter sees it, so "is it a non-empty object" is no longer the adapter's question — the schema already answered it. With class-transformer the check never fired because declared-but-absent fields were present as undefined; with zod (strip mode) {} stays {}.

Suggested fix

• RepositoryAdapter.prepare: keep the non-object guard, drop the zero-keys guard (Object.assign(new Entity(), {}) is a valid, empty entity).
• CrudAdapter.prepareEntityBeforeSave: same — keep isObject, drop Object.keys(merged).length.
• If a rejection is kept anywhere, give it a message (BadRequestException('Request body must be a JSON object')).

Workaround in Rockets

RocketsCrudAdapter (a CrudAdapter subclass) overrides prepareEntityBeforeSave and builds new (this.entityType())() when prepare() returns undefined for an empty object. Reference: conceptadev/rockets#105 (packages/rockets-core/src/infrastructure/crud/rockets-crud.adapter.ts, e2e in rockets-core-sub-resource.e2e-spec.ts).

[MrMaz]

Fixed with #466