JSONFormatter and normalizing of PHP objects

[digilist]

Monolog version 2

Not sure if this is really a bug report or rather a feature request. But I noticed that some objects in the log context are not normalized like it is via the NormalizerFormatter and therefore disappear when using the JsonFormatter.

As an example, I am refering to the Symfony AuthenticatorManager that is writing a "Authenticator successful" log message after a successful authentication:

https://github.com/symfony/symfony/blob/25c2bb1c7c2f1d1f32955c5f0365ccbfcc447137/src/Symfony/Component/Security/Http/Authentication/AuthenticatorManager.php#L204

You can see there as well that the token is added to the log context (in my example it is an instance of UsernamePasswordToken).

On successful authentication and when using the StreamHandler with the default NormalizerFormatter, the output looks like this:

[2022-07-09T17:31:16.113589+02:00] security.INFO: Authenticator successful! {"token":{"Symfony\\Component\\Security\\Core\\Authentication\\Token\\UsernamePasswordToken":"UsernamePasswordToken(user=\"foo@bar.com\", roles=\"ROLE_USER\")"},"authenticator":"Symfony\\Component\\Security\\Http\\Authenticator\\FormLoginAuthenticator"} {}

And when the JsonFormatter is used, it looks like this:

{"message":"Authenticator successful!","context":{"token":{},"authenticator":"Symfony\\Component\\Security\\Http\\Authenticator\\FormLoginAuthenticator"},"level":200,"level_name":"INFO","channel":"security","datetime":"2022-07-09T17:31:16.113589+02:00","extra":{}

As you can see, the token disappeared. I already did a bit of investigation and noticed that in the NormalizerFormatter::normalize() method contains some logic for objects:

monolog/src/Monolog/Formatter/NormalizerFormatter.php

Lines 189 to 207 in 100d0f1

	if (is_object($data)) {
	if ($data instanceof Throwable) {
	return $this->normalizeException($data, $depth);
	}
	if ($data instanceof \JsonSerializable) {
	/** @var null|scalar|array<mixed[]|scalar|null> $value */
	$value = $data->jsonSerialize();
	} elseif (method_exists($data, '__toString')) {
	/** @var string $value */
	$value = $data->__toString();
	} else {
	// the rest is normalized by json encoding and decoding it
	/** @var null|scalar|array<mixed[]|scalar|null> $value */
	$value = json_decode($this->toJson($data, true), true);
	}
	return [Utils::getClass($data) => $value];
	}

The JsonFormatter::normalize() doesn't contain such logic.

My guess is that objects are not serialized, because json_encode is taking care of it. However, private fields in PHP are not part of the encoded JSON and therefore the information gets lost.

My suggestion for a fix would be to add a similar logic for the JSON normalizer if the objects implements JSONSerializable or has a __toString() method. What do you think about it? I can provide a PR if this proposal sounds reasonable to you.

[Seldaek]

JSONSerializable is already handled internally by json_encode, which is why there was no speical object treatment, but we need to add toString if it's present too.

[digilist]

Thank you! 😊