Keep nesting shallow

How to do it

Return early with guard clauses for the cases that stop. Move the body of a deep loop into its own named function. Replace long if chains with a lookup table or polymorphism. Where the outer level is a switch or match that picks a case, allow one more level. Then move each case body into its own function.

Example

// Bad
function ship(Order $order) {
    if ($order->isPaid()) {
        if ($order->hasStock()) {
            if (!$order->isShipped()) { $this->courier->send($order); }
        }
    }
}

// Good
function ship(Order $order): void {
    if (!$order->isPaid() || !$order->hasStock() || $order->isShipped()) {
        return;
    }
    $this->courier->send($order);
}

# Good: guard clauses keep the main path at one level
def ship(order):
    if not order.is_paid() or not order.has_stock() or order.is_shipped():
        return
    courier.send(order)

How to check

The build fails above the limit. Examples are ESLint max-depth set to 2, or 3 in files that dispatch with switch. PHP_CodeSniffer Generic.Metrics.NestingLevel with absoluteNestingLevel set to 2 and Pylint too-many-nested-blocks with max-nested-blocks=2 do the same.