Woocommerce Direct Checkout

wcdco.php

//Skip Cart & Redirect To Checkout 
add_filter( 'woocommerce_add_to_cart_redirect', 'custom_add_to_cart_redirect' );
function custom_add_to_cart_redirect() {
    global $woocommerce;
    $checkout_url = $woocommerce->cart->get_checkout_url();
    return $checkout_url;
}

wcqcco.php

// Add quantity field to checkout page
add_action( 'woocommerce_checkout_before_order_review', 'add_quantity_field_to_checkout' );
function add_quantity_field_to_checkout() {
    foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
        $_product = apply_filters( 'woocommerce_cart_item_product', $cart_item['data'], $cart_item, $cart_item_key );
        ?>
        <div class="quantity">
            <label class="screen-reader-text" for="quantity_<?php echo $cart_item_key; ?>"><?php esc_html_e( 'Quantity', 'woocommerce' ); ?></label>
            <input type="number" id="quantity_<?php echo $cart_item_key; ?>" class="input-text qty text" step="1" min="1" name="cart[<?php echo $cart_item_key; ?>][qty]" value="<?php echo $cart_item['quantity']; ?>" title="<?php esc_attr_e( 'Qty', 'woocommerce' ); ?>" size="4" inputmode="numeric" />
        </div>
        <?php
    }
}

// Update cart item quantity on checkout update
add_action( 'woocommerce_checkout_update_order_review', 'update_cart_item_quantity_on_checkout' );
function update_cart_item_quantity_on_checkout( $post_data ) {
    foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
        if ( isset( $post_data['cart'][$cart_item_key]['qty'] ) ) {
            $quantity = wc_stock_amount( sanitize_text_field( $post_data['cart'][$cart_item_key]['qty'] ) );
            WC()->cart->set_quantity( $cart_item_key, $quantity, false );
        }
    }
}