Union type support for structured outputs

[HaKIMus]

Unfortunately \Symfony\AI\Platform\Contract\JsonSchema\Factory::getTypeSchema doesn't support for \Symfony\Component\TypeInfo\Type\UnionType.

What I'm trying to achieve:

<?php

declare(strict_types=1);

namespace App\Agent\Application\StructuredOutput;

use Webmozart\Assert\Assert;

final class ChatStructuredOutput
{
    public function __construct(
        public string $title,
        public string $finalAnswer,
        /** @var array<int, ChartPart | TablePart | TextPart> */
        public array $parts = [],
    ) {
        Assert::allIsInstanceOf($this->parts, StructuredOutputPart::class);;
    }
}

It's quite possible I'm using the structured output wrong, and I should deal with the problem differently. I'm all ears how could I make it work.

[OskarStark]

Nice one, but how would the final schema look like, can we add some "or" conditions?

[HaKIMus]

There is the "oneOf" option that we could map union types to.

[OskarStark]

Lets give it a try, yes

[HaKIMus]

Just a note: "oneOf" isn't supported (at least by GPT) in the strict mode. "anyOf" is being recommended. Info based on my hacking-attempt and this article: https://community.openai.com/t/oneof-allof-usage-has-problems-with-strict-mode/966047

I've made it almost* work, but I can't figure out why my parts aren't being serialized to objects like reasoningStep is. :/

[aszenz]

Claude models support for complex json schema is better, I couldn't get open api to output a complex json as per spec but Claude had no issues

[OskarStark]

So creating a PR including an example for claude would be good then 👍

[HaKIMus]

@OskarStark I've just updated the PR with native union types support. Not exactly what I needed, but I think the PR caused a bit confusion with the DiscriminatorMap which solves the case of (@param list<TypeA|TypeB>) that I couldn't make symfony serializer to handle.