Feature request: add syntax to prevent preprocessing

[woodholly]

Description

The Problem:

$logger->debug('action', [
    'user' => $user->toArray(),
    'trace' => debug_backtrace(),
]);

That debug_backtrace() runs every time, eats CPU, RAM, even when debug is off. PHP evaluates arguments before the call. Always.

Current Workarounds Suck:

if ($logger->isHandling(Logger::DEBUG)) {
    $logger->debug('action', $expensiveStuff);
}

Closure - can't capture locals cleanly:

$logger->debug('action', fn() => ['user' => $user, 'x' => $x, 'y' => $y]);

Short-circuit - inverted logic, looks like a bug, globals:

$noDebug or $logger->debug('action', $expensive);

So, last hope - build postprocessor to remove debug ? - are we writing C?

Proposed: lazy Keyword

function debug(string $msg, lazy array $context = []): void {
    if (!$this->enabled) return;  // $context never evaluated
    $this->write($msg, $context); // evaluated here
}

Usage stays clean:

$logger->debug('action', ['trace' => debug_backtrace()]);

Other Use Cases

assert(lazy $obj->isValid(), lazy $obj->getErrorMessage());
$cache->remember('key', lazy $this->heavyQuery());

Kotlin, Swift, Scala, Rust all have this. PHP doesn't.

[iluuu1994]

Hi @woodholly.

Kotlin, Swift, Scala, Rust all have this. PHP doesn't.

I know Swift has it (@autoclosure), but I'm not aware of the same feature in other languages? I feel like this is effectively just asking for shorter closure syntax again.

It's very unclear to me how this would work without some syntax hint. PHP works differently from compiled languages, in that we don't know whether a parameter is marked as lazy when the local file is compiled.

Furthermore, I think this feature is also quite controversial, because it changes expectations of when or even if arguments are executed.

Please start a discussion on the mailing list to see whether people would be interested in something similar. Maybe somebody there will have an idea on how this could even work.