# schema-constraints

Source: https://apigenie.pl/docs/linter/asyncapi/rules/schema-constraints

This rule ensures that schema objects define constraints restricting the size
of the underlying data.

## Rule Details

Defining constraints enhances the robustness and reliability of the API's
structure, and protects consumers from unexpectedly large messages.

The `schema-constraints` rule checks every schema of an AsyncAPI document
(component schemas, message payloads and headers, parameter schemas, and all
schemas nested in them) and requires, depending on the schema type:

- integers - both a lower bound (`minimum` or `exclusiveMinimum`) and an upper
  bound (`maximum` or `exclusiveMaximum`),
- numbers - both a lower bound and an upper bound, as for integers,
- strings - `maxLength`, `pattern`, `format` or `enum`,
- arrays - `maxItems`,
- objects - `maxProperties`, or `additionalProperties: false`.

A schema with several types (e.g. `type: [string, integer]`) is checked for
each of them. The reported messages are `Integer schema does not define
constraints restricting its range`, `Numeric schema does not define
constraints restricting its range`, `String schema does not define constraints
restricting its length`, `Array schema does not define constraints restricting
its size` and `Object schema does not define constraints restricting its
size`.

## Configuration

The configuration should be an object whose keys are supported schema types,
and values are boolean values. Only the types set to `true` are checked, and
at least one schema type must be set to `true`.

Supported schema types are `integer`, `number`, `string`, `array` and
`object`.

By default, constraints for all supported schema types are verified. The
`recommended` ruleset checks only `number` and `string` schemas.

**Configuration Example**. The rule with the following configuration checks
only array and object schemas, and does not check numbers and strings.

```yaml
version: "1.0"
commands:
  lint:
    asyncapi:
      rules:
        schema-constraints:
          - warning
          - array: true
            object: true
```

## Examples

**Good**.

```yaml
asyncapi: 3.0.0
info:
  title: User Events
  version: 1.0.0
components:
  schemas:
    User:
      type: object
      properties:
        username:
          type: string
          maxLength: 20
          pattern: "^[a-z0-9_-]{3,16}$"
        roles:
          type: array
          items:
            type: string
            enum: [admin, member]
          maxItems: 5
        age:
          type: integer
          minimum: 18
          maximum: 100
      maxProperties: 3
```

**Bad**.

```yaml
asyncapi: 3.0.0
info:
  title: User Events
  version: 1.0.0
components:
  schemas:
    User:
      type: object
      properties:
        username:
          type: string
        roles:
          type: array
          items:
            type: string
        age:
          type: integer
```

## When Not to Use It

If your API does not require specific constraints on its schema objects,
you may not need to use this rule.

## Compatibility

This rule is compatible with AsyncAPI 3.x documents. AsyncAPI 2.x documents
are rejected by the reader and are not linted.