# boolean-parameter-prefixes

Enforces specific and consistent naming for request parameters with `boolean` type.
When this rule is enabled, the `name` fields of all `boolean` parameters in your API must contain one of the configured prefixes.

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



```mermaid
flowchart TD

root ==> Paths --> PathItem --> Operation --> Parameter --enforces names for boolean 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

Consistency in API design makes APIs easier to use.
Being able to identity boolean types from their names is possible when they use consistent prefixes, such as `is` or `has`.
If you saw an API with these parameters, you could identify the boolean parameters by their names:

- orderNumber
- amount
- hasPaid
- shippingService
- isFulfilled
- customerReference


The nuance of being able to identify the boolean parameters helps developers produce and consume APIs.

## Configuration

| Option | Type | Description |
|  --- | --- | --- |
| severity | string | Possible values: `off`, `warn`, `error`. Default `off`. |
| prefixes | [string] | List of allowed boolean parameter prefixes. Default values are `is` and `has`. |


An example configuration:


```yaml
rules:
  boolean-parameter-prefixes: error
```

The following example configures prefixes:


```yaml
rules:
  boolean-parameter-prefixes:
    severity: error
    prefixes: ["can", "is", "has"]
```

## Examples

Given the configuration with the prefixes `can`, `is`, and `has`, the following example shows an error.

Example of **incorrect** boolean parameter prefixes:


```yaml
schema:
  type: object
  properties:
    belongsToUser:
      type: boolean
      default: false
```

Example of **correct** boolean parameter prefixes:


```yaml
schema:
  type: object
  properties:
    isUser:
      type: boolean
      default: false
```

## Related rules

- [configurable rules](/docs/cli/rules/configurable-rules)
- [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 2.0](https://github.com/Redocly/redocly-cli/blob/main/packages/core/src/rules/oas2/boolean-parameter-prefixes.ts)
- [Rule source for OAS 3.0 and 3.1](https://github.com/Redocly/redocly-cli/blob/main/packages/core/src/rules/oas3/boolean-parameter-prefixes.ts)
- [OpenAPI Parameter](https://redocly.com/docs/openapi-visual-reference/parameter/) docs