# json-api/resource-type-unique

Source: https://apigenie.pl/docs/linter/openapi/rules/json-api-resource-type-unique

This rule ensures that all resource schemas in a JSON:API have unique resource
IDs.

## Rule Details

Within the JSON:API specification a uniqueness of a resource depends on a
uniqueness of its type. Therefore, we need a way to check the latter.

The `json-api/resource-type-unique` rule is designed to ensure that all
resource schemas in a JSON:API have unique resource IDs. This rule is
specifically useful for APIs that adhere to the JSON:API specification.

To determine the resource type, the rule checks both the `const` and `enum`
properties of corresponding JSON schemas.

## Configuration

None.

## Examples

**Good**. The following schema defines two resources with unique types.

```yaml
openapi: 3.1.0
info: ...
paths: ...
components:
  schemas:
    User:
      type: object
      properties:
        type:
          type: string
          const: user
        ...
    Employee:
      type: object
      properties:
        type:
          type: string
          enum:
            - employee
        ...
```

**Bad**. The following schema does not define allowed value for a resource.

```yaml
openapi: 3.1.0
info: ...
paths: ...
components:
    schemas:
        User:
            type: object
            properties:
                type:
                    # this property does not specify allowed values
                    type: string
                ...
```

**Bad**. The following schema defines two distinct resources with identical
resource types.

```yaml
openapi: 3.1.0
info: ...
paths: ...
components:
    schemas:
        User:
            type: object
            properties:
                type:
                    type: string
                    const: person
                ...
        Employee:
            type: object
            properties:
                type:
                    type: string
                    enum:
                        - person
                ...
```

## When Not to Use It

When you do not use the JSON:API specification.

## Compatibility

This rule is compatible with all OpenAPI 3.x version.