[12.x] Do not dispatch MessageLogged twice

[cosmastech]

This is related to laravel/pail#52

If you call app(\Illuminate\Log\Logger::class)->debug("Totwells - Taylor Otwell's Arkansas style tater tots") using Pail (and I would bet Telescope too), it will record two separate log entries, because they react to the MessageLogged event.

Instantiating Logger sets the $logger instance to LogManager. Therefore, the Logger class and its $logger both dispatch the event.

[taylorotwell]

Where and how do both dispatch the event?

[cosmastech]

Where and how do both dispatch the event?

@taylorotwell

When you build the \Illuminate\Log\Logger, the container supplies a LogManager for the $logger instance.

Therefore, $logger->debug() calls $logger->logger->debug(). This means Logger calls LogManager which will call another Logger instance. So the original Logger instance in userland will dispatch the MessageLogged event AFTER the LogManager calls its Logger instance, which will have already dispatched the MessageLogged event.

[cosmastech]

sequenceDiagram
    autonumber
    participant U as Userland code
    participant LA as Illuminate\Log\Logger (outer)
    participant LM as Illuminate\Log\LogManager
    participant LB as Illuminate\Log\Logger (inner/channel)
    participant M as Monolog\Logger
    participant E as Event Dispatcher

    U->>LA: debug("...")
    activate LA
    LA->>LM: debug("...")
    activate LM
    LM->>LB: resolve channel → debug("...")
    activate LB
    LB->>M: debug()
    M-->>LB: write complete
    LB->>E: dispatch MessageLogged (1st)
    deactivate LB
    LM-->>LA: return
    deactivate LM
    LA->>E: dispatch MessageLogged (2nd)
    deactivate LA

Loading

here's a chart that ChatGippity generated for me to demonstrate.