[BUG] [SWIFT] Array items cannot be nullable

[dan-magnusson-lowes]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

In the Swift 6 codegen array item types cannot be nullable.

openapi-generator version

Latest: 7.17.0
Not a regression

OpenAPI declaration file content or url

        ArrayWithNullableItemsModel:
          required:
            - foo
          properties:
            foo:
              type: array
              items:
                type: string
                nullable: true

Generation Details

Expected:

public struct ArrayWithNullableItemsModel: Sendable, Codable, ParameterConvertible, Hashable {

    public var foo: [String?]

    public init(foo: [String?]) {
        self.foo = foo
    }
    ...
}

Actual:

public struct ArrayWithNullableItemsModel: Sendable, Codable, ParameterConvertible, Hashable {

    public var foo: [String]

    public init(foo: [String]) {
        self.foo = foo
    }
    ...
}

Steps to reproduce

See above.

Related issues/PRs

#19070 - Kotlin bug report
#19080 - Kotlin PR
#19157 - TypeScript PR

Suggest a fix

On line 742:

openapi-generator/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java

Line 742 in fd72d4d

return ModelUtils.isSet(p) ? "Set<" + getTypeDeclaration(inner) + ">" : "[" + getTypeDeclaration(inner) + "]";

Account for nullable item schemas in the way the Kotlin generator does since PR 19080, with a getItemsTypeDeclaration(Schema items) function.