# IncomingResponseDeserializer

**Kind:** Class

**Source:** [`packages/microservices/deserializers/incoming-response.deserializer.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/deserializers/incoming-response.deserializer.ts#L7)

**Part of:** [Microservices](subsystem-packages-microservices)

`IncomingResponseDeserializer` normalizes responses received by microservice transports into the internal `IncomingResponse` schema. It detects whether a value is already in the expected envelope format and wraps external/raw responses when necessary, allowing downstream response handling to use a consistent structure.

**Implements:** `ProducerDeserializer`

## Methods

| Method | Signature | Returns |
|---|---|---|
| `deserialize` | `deserialize(value: any, options: Record<string, any>)` | `IncomingResponse` |
| `isExternal` | `isExternal(value: any)` | `boolean` |
| `mapToSchema` | `mapToSchema(value: any)` | `IncomingResponse` |

## Where it refuses work

- `IncomingResponseDeserializer` stops the work with an early return when `!value`.
- `IncomingResponseDeserializer` stops the work with an early return when `!isUndefined((value as IncomingResponse).err) || !isUndefined((value as IncomingResponse)…`.

## Diagram

```mermaid
graph LR
  A[Raw transport response] --> B[deserialize]
  B --> C{isExternal?}
  C -- No --> D[Return existing IncomingResponse]
  C -- Yes --> E[mapToSchema]
  E --> F[Normalized IncomingResponse]
```

## Usage

```ts
import { IncomingResponseDeserializer } from '@nestjs/microservices';

const deserializer = new IncomingResponseDeserializer();

const rawResponse = {
  id: 'request-42',
  data: { status: 'ok' },
};

const response = deserializer.deserialize(rawResponse);

console.log(response.id); // "request-42"
console.log(response.response); // original raw response payload
console.log(response.isDisposed); // true
```

## AI Coding Instructions

- Use `deserialize()` as the public entry point; do not call `mapToSchema()` directly unless extending the deserialization behavior.
- Preserve already-normalized `IncomingResponse` objects instead of wrapping them again.
- Keep `isExternal()` aligned with the response envelope contract used by the active microservice transport.
- When changing the mapped schema, verify compatibility with downstream client response handling and request correlation via `id`.

## Relationships

- IMPORTS → `isUndefined`