[AIBundle] Improve injection aliases

[Guikingone]

Q	A
Bug fix?	no
New feature?	yes
Docs?	no
Issues	None
License	MIT

Hi 👋🏻

This PR aims to add "injection aliases", those allows the user to use the following code while defining X agents:

public function __construct(
    private AgentInterface $fooAgent,
) {
}

Why the Agent suffix? Because we don't know, maybe one day, a service will be called foo and it will trigger an error, it seems better to define a suffix and ensure that this bundle is the only one to use it.

[OskarStark]

Shouldn't it be $myAgentAgent?

[Guikingone]

Well, I'm not sure, while adding the call, the container export the service definition as the following:

<service id="Symfony\AI\Agent\AgentInterface $fooAgent" alias="ai.agent.foo"/>

I bet Symfony is exporting the service along with the FQCN, don't know why to be fair but looks like the "default behavior" 🤔

[OskarStark]

Your name is my_agent, so IMHO it should be myAgent + Agent suffix, to be more clear, I would expect $fooBarAgent when I name it foo_bar and not $foo_barAgent. How does Monolog is converting the names for example or HttpClient?

[Guikingone]

Well, regarding the method:

/**
 * Registers an autowiring alias that only binds to a specific argument name.
 *
 * The argument name is derived from $name if provided (from $id otherwise)
 * using camel case: "foo.bar" or "foo_bar" creates an alias bound to
 * "$fooBar"-named arguments with $type as type-hint. Such arguments will
 * receive the service $id when autowiring is used.
 */
public function registerAliasForArgument(string $id, string $type, ?string $name = null): Alias
{
    $parsedName = (new Target($name ??= $id))->getParsedName();

    if (!preg_match('/^[a-zA-Z_\x7f-\xff]/', $parsedName)) {
        if ($id !== $name) {
            $id = \sprintf(' for service "%s"', $id);
        }

        throw new InvalidArgumentException(\sprintf('Invalid argument name "%s"'.$id.': the first character must be a letter.', $name));
    }

    if ($parsedName !== $name) {
        $this->setAlias('.'.$type.' $'.$name, $type.' $'.$parsedName);
    }

    return $this->setAlias($type.' $'.$parsedName, $id);
}

It look like Sf is not doing the job properly, here's the method usage for HttpClient's:

$container->registerAliasForArgument($name, HttpClientInterface::class);

if ($hasPsr18) {
    $container->setDefinition('psr18.'.$name, new ChildDefinition('psr18.http_client'))
        ->replaceArgument(0, new Reference($name));

    $container->registerAliasForArgument('psr18.'.$name, ClientInterface::class, $name);
}

if ($hasHttplug) {
    $container->setDefinition('httplug.'.$name, new ChildDefinition('httplug.http_client'))
        ->replaceArgument(0, new Reference($name));

    $container->registerAliasForArgument('httplug.'.$name, HttpAsyncClient::class, $name);
}

BTW, If I try to define a custom agent in my application called translation, the resolved argument is translationAgent.

[Guikingone]

Regarding Monolog, there's nothing more in the extension:

protected function createLogger(string $channel, string $loggerId, ContainerBuilder $container)
{
    if (!in_array($channel, $this->channels)) {
        $logger = new ChildDefinition('monolog.logger_prototype');
        $logger->replaceArgument(0, $channel);
        $container->setDefinition($loggerId, $logger);
        $this->channels[] = $channel;
    }

    $parameterName = $channel . 'Logger';

    $container->registerAliasForArgument($loggerId, LoggerInterface::class, $parameterName);
}

[Guikingone]

Ok, found the issue.

Looks like if you set foo_toto, Symfony resolve it as fooToto, the catch is that if the $name is not the same as the parsed name:

if ($parsedName !== $name) {
    $this->setAlias('.'.$type.' $'.$name, $type.' $'.$parsedName);
}

In this case, the $name is used (so foo_toto) rather than fooToto (the parsed one) 🤔

EDIT:

One solution might be to call the Target class while defining the alias:

$container->registerAliasForArgument('ai.agent.'.$name, AgentInterface::class, (new Target($name.'Agent'))->getParsedName());

[OskarStark]

Thanks for digging, I am fine either way, but would like to end with $myAgentAgent for my_agent 😄

Maybe something which can be unified? cc @nicolas-grekas