[Agent] Support translations for system input processor

[paulinevos]

So that system prompts can be written in any locale

Q	A
Bug fix?	no
New feature?	yes
Docs?	no (there's no documentation for system input, so not sure where to put it. Open to ideas!
Issues	Fix #370
License	MIT

This adds an optional translator to the SystemInputProcessor which, if set, will translate the configured system prompt.

[OskarStark]

Can we please make the translator configurable in the bundle? Thanks

[chr-hertel]

so, what we just discussed as config structure:

system_prompt:
    prompt: '...',
    enable_translation: true|false, # default: true if translator is present
    translation_domain: '...', # default: "messages"
    include_tools: true|false # default same as now

[VincentLanglet]

so, what we just discussed as config structure:

    enable_translation: true|false, # default: true if translator is present
    translation_domain: '...', # default: "messages"

@chr-hertel I feel like this is kinda redundant, you could have only one key by allowing string|null (default to message)|false like lot of other places where translation is used

[OskarStark]

You are right, but it's some kind of a hidden feature. It's not clear, that string or null means, the translator is enabled. So lets go with @chr-hertel proposal

[VincentLanglet]

Speaking of symfony/translation-contracts, there is a TranslatableInterface.

Not sure if it would be better to have

public function __construct(
        private \Stringable|string|Translatable $systemPrompt,
        private ?ToolboxInterface $toolbox = null,
        private ?TranslatorInterface $translator = null,
        private LoggerInterface $logger = new NullLogger(),
    ) {	
         if ($systemPrompt instanceof Translatable && null === TranslatorInterface) {
              throw new InvalidArgumentException(...);
         }
    }
    
private function translateIfEnabled(): string
{
     if ($systemPrompt instance Translatable) {
          return $systemPrompt->trans($this->translator);
     }
     
     return (string) $systemPrompt;
}    

And the AiBundle

if ($config['prompt']['enable_translation']) {
     if (!class_exists(TranslatableMessage::class) {
          throw new InvalidArgumentException('Please install symfony/translation');
     }
     
     $prompText = new TranslatableMessage($config['prompt']['text'], domain: $config['prompt']['translation_domain']);
} else {
     $prompText = $config['prompt']['text'];
}

...
->setArguments([
                    $prompText,
                    $includeTools ? new Reference('ai.toolbox.'.$name) : null,
                    new Reference('translator', ContainerInterface::NULL_ON_INVALID_REFERENCE),
                    new Reference('logger', ContainerInterface::IGNORE_ON_INVALID_REFERENCE),
])

This can also be done in another pr

[paulinevos]

Hmm, I'm not super convinced about using TranslatableMessage in this way, as it seems to add some complexity for a fairly simple use case and it puts a lot of behavior in the bundle that (in my eyes) "belongs to" SystemPromptInputProcessor

[OskarStark]

Shall we do this validation in the constructor?

[VincentLanglet]

Hmm, I'm not super convinced about using TranslatableMessage in this way, as it seems to add some complexity for a fairly simple use case and it puts a lot of behavior in the bundle that (in my eyes) "belongs to" SystemPromptInputProcessor

We could argue the opposite.

Currently we're adding complexity in SystemPromptInputProcessor which has to be aware about

• if we want enable translation or not
• the translation domain

Such things should be "prompt" knownledge rather than SystemPromptInputProcessor one. Quoting the original PR symfony/symfony#37670

The service shouldn't need to care how the message is going to be handled, but just needs to create it in a way that it can be translated if needed.

TranslatableMessage is a way to avoid putting this knownledge inside the SystemPromptInputProcessor

It's also a way to allow using translation parameters.

[OskarStark]

It took time, but here we go, this is in now. Thank you very much @paulinevos.

[VincentLanglet]

@OskarStark would you be interested with a Poc with translatableMessage ?

[OskarStark]

Why not, shouldn't be to much code, right?