Error Codes - Loopback Next

In order to allow clients to reliably detect individual error causes, LoopBack sets the error code property to a machine-readable string.

ENTITY_NOT_FOUND

The entity (model) was not found. This error is returned for example by EntityCrudRepository.prototype.findById.

VALIDATION_FAILED

The data provided by the client is not a valid entity.

INVALID_PARAMETER_VALUE

The value provided for a parameter of a REST endpoint is not valid. For example, a string value was provided for a numeric parameter.

MISSING_REQUIRED_PARAMETER

No value was provided for a required parameter.

CANNOT_INFER_PROPERTY_TYPE

LoopBack is using TypeScript design-time type metadata to automatically infer simple property types like string, number or a model class.

In the following example, the type of the property name is inferred from TypeScript metadata as string.

@model()
class Product {
  @property()
  name: string;
}

Design-time property type is not available in the following cases:

The property has a type not supported by TypeScript metadata engine:
- undefined
- null
- complex types like arrays (string[]), generic types (Partial<MyModel>), union types (string | number), and more.
The TypeScript project has not enabled the compiler option emitDecoratorMetadata.
The code is written in vanilla JavaScript.

Solutions

You have the following options how to fix the error CANNOT_INFER_PROPERTY_TYPE:

If you are using TypeScript, make sure emitDecoratorMetadata is enabled in your compiler options.

json

{
  "$schema": "http://json.schemastore.org/tsconfig",
  "compilerOptions": {
    "emitDecoratorMetadata": true
  }
}

A typical LoopBack project is inheriting compiler options from @loopback/build, where emitDecoratorMetadata is already enabled.

json

{
  "$schema": "http://json.schemastore.org/tsconfig",
  "extends": "@loopback/build/config/tsconfig.common.json"
}

If your property uses a complex type, then specify the type in the type field of @property() definition.
ts
```
@model()
class UserProfile {
  @property({type: 'string'})
  hourFormat: '12h' | '24h';
}
```

Other error codes

Besides LoopBack-specific error codes, your application can encounter low-level error codes from Node.js and the underlying operating system. For example, when a connector is not able to reach the database, an error with code ECONNREFUSED is returned.

See the following resources for a list of low-level error codes: