# array-parameter-serialization

Enforces the inclusion of `style` and `explode` fields for parameters with array type or parameters with a schema that includes `items` or `prefixItems`.

| OAS | Compatibility |
|  --- | --- |
| 2.0 | ❌ |
| 3.0 | ✅ |
| 3.1 | ✅ |



```mermaid
flowchart TD

root ==> Paths --> PathItem --> Operation --> Parameter --enforces style and explode fields for array types--> Schema
PathItem --> Parameter
NamedParameter --> Parameter

root ==> components

subgraph components
NamedParameter
end

style Parameter fill:#codaf9,stroke:#0044d4,stroke-width:5px
style Schema fill:#codaf9,stroke:#0044d4,stroke-width:5px
```

## API design principles

Specifying serialization details consistently helps developers understand how to interact with the API effectively.

## Configuration

| Option | Type | Description |
|  --- | --- | --- |
| severity | string | Possible values: `off`, `warn`, `error`. Default `off`. |
| in | [string] | List of valid parameter locations where the rule should be enforced. By default the rule applies to parameters in all locations. |


An example configuration:


```yaml
rules:
  array-parameter-serialization:
    severity: error
    in:
      - query
      - header
```

## Examples

Given this configuration:


```yaml
rules:
  array-parameter-serialization:
    severity: error
    in:
      - query
```

Example of **incorrect** parameter:


```yaml
paths:
  /example:
    get:
      parameters:
        - name: exampleArray
          in: query
          schema:
            type: array
            items:
              type: string
```

Example of **correct** parameter:


```yaml
paths:
  /example:
    get:
      parameters:
        - name: exampleArray
          in: query
          style: form
          explode: true
          schema:
            type: array
            items:
              type: string
```

## Related rules

- [configurable rules](/docs/cli/rules/configurable-rules)
- [boolean-parameter-prefixes](/docs/cli/rules/oas/boolean-parameter-prefixes)
- [no-invalid-parameter-examples](/docs/cli/rules/oas/no-invalid-parameter-examples)
- [parameter-description](/docs/cli/rules/oas/parameter-description)
- [operation-parameters-unique](/docs/cli/rules/oas/operation-parameters-unique)


## Resources

- [Rule source for OAS 3.0 and 3.1](https://github.com/Redocly/redocly-cli/blob/main/packages/core/src/rules/oas3/array-parameter-serialization.ts)
- [OpenAPI Parameter](https://redocly.com/docs/openapi-visual-reference/parameter/) docs