Add an order setting to disable multiple checkout completion invocations per order

I was thinking the same thing.
Do you already programmed this solution? Maybe a hack..

I have faced the same issue and solved it by using a custom database table. Please look into the below code snippet.

function mymodule_commerce_checkout_complete($order) {
$uid = $order->uid;
$nid = $order->data['lnid'];
$order_id = $order->order_id;
// this hook is called twice while order completion
$query = db_select('custom_commerce_checkout_complete', 'ccc')
->fields('ccc', array('order_id'))
->condition('ccc.nid', $nid, '=')
->condition('ccc.order_id', $order_id, '=');
$result = $query->execute();

if($result->rowCount() == 0) {
db_merge('custom_commerce_checkout_complete')
->key(array('nid' => $nid, 'order_id' => $order_id))
->fields(array(
'uid' => $uid,
'nid' => $nid,
'order_id' => $order_id,
))
->execute();
// call your function here
example_send_mail($order);
}
}

This request makes sense, however, it is considered a breaking change. Recategorized to feature request as this is not strictly a defect or bug.

I'm highly sensitive to implementing breaking changes, and it is technically true that prior to this change, a site could have been dependent on multiple checkout completions being possible. (For example, a paid order being update and sent back to a cart status for a customer to provide additional payment. It's a stretch, but it was possible.)

That said, I think the default expectation that this should only be fired once is the vast majority use case and would apparently resolve some race condition related errors in payment contribs. I'm going to add a setting that a developer can add to their settings.php file to permit multiple checkout completions and call that out in the release notes as something developers need to manually do if needed.

Actually ... I see that my original comment does specifically identify the "admin edits and customers re-checkout" potential. We've been saying that for years, I'd hate to screw that up.

What I think we'll do instead is add a toggle to the order settings form similar to the options there for shopping cart orders. This checkbox will be labeled, "Permit checkout completion logic to be invoked multiple times per order."

It will be enabled by default on existing sites via an update hook. For new sites, it will be disabled by default.

This does mean folks like @Anybody will need to toggle this off after updating, but I think that's a reasonable compromise all around.

Changing my mind again given the current functioning of the "Simulate checkout completion" button in the order admin interface. I think the simplest thing to do is to leave the default option for the new setting to TRUE, meaning even for new sites we will still permit checkout completion to be performed multiple times. I'll just add a description to it that says it may not be supported for off-site payment gateways, and I'll check the setting in the form builder function for the simulate checkout completion before permitting form submission.

As a minor improvement on the model of storing a rule invocation in $order->data as a boolean, I've opted for a timestamp instead. Will still evaluate empty() the same way. I'm going to open an issue for a similar change in payment, because the timestamp could actually be useful for debug purposes.

Patch attached.

Committing.

@Anybody my pleasure! Thanks for your multiple contributions to this recent release!