# schema-conditional-effective

Source: https://apigenie.pl/docs/linter/openapi/rules/schema-conditional-effective

This rule checks that `if`, `then` and `else` in schemas have an effect.

## Rule Details

JSON Schema applies `then` to values matching `if` and `else` to the other values.
Several combinations silently do nothing, usually because of a typo or a keyword placed
at the wrong level:

- `then` or `else` without `if` is ignored.
- `if` without `then` and `else` has no effect.
- `else` never applies when `if` accepts every value, e.g. `if: {}` or an `if` with only
  a `description`; `then` never applies when `if` is `false`.
- `then` or `else` accepting every value (e.g. `{}`) has no effect.

References are followed, so `if: {$ref: ...}` is checked against the referenced schema.

## Configuration

None.

## Examples

**Good**. Card payments require a card number, the others an IBAN.

```yaml
components:
  schemas:
    Payment:
      type: object
      if:
        properties:
          kind:
            const: card
      then:
        required: [cardNumber]
      else:
        required: [iban]
```

**Bad**. `then` is ignored because the schema has no `if`.

```yaml
components:
  schemas:
    Payment:
      type: object
      then:
        required: [cardNumber]
```

## When Not to Use It

We recommend to always enable this rule.

## Compatibility

This rule applies to OpenAPI 3.1 and later, where `if`, `then` and `else` are schema
keywords. OpenAPI 3.0 documents are skipped.