How to fix onSubmit data validation once and for all in Scoped Applica

So a little background. I have a Scope Application which has a catalog item. I wanted the ability to verify a file was attached prior to submission. The problem is, most all solutions proposed do not work in scoped applications...

Here are the current solutions you could use if you were not in a scoped application:

1) You could use GlideAjax and do a getXMLWait(), then check the answer and return false, example:

var ga = new GlideAjax('MyAttachmentUtils');  
ga.addParam('sysparm_name', 'hasAttachment');  
ga.addParam('sysparm_data', g_form.getValue('sysparm_item_guid')); // you can't use getUniqueValue, it doesn't map to what is in the attachment table  
ga.getXMLWait();  
if (ga.getAnswer() == 'false') {  
    g_form.addErrorMessage('You must attach something');  
    return false;  
}

All fine and dandy (if you are ok with using getXMLWait)...but, of course, getXMLWait is NOT available in scoped applications (makes sense, they don't want apps locking up the browser...

So...on to option 2

2) You could move your code from your script include directly into the client script...Then use GlideRecord and do the search in the client script!

var gr = new GlideRecord('sys_attachment');  
gr.addQuery('table', 'my_table');  
gr.addQuery('table_sys_id', g_form.getValue('sysparm_item_guid'));  
gr.query();  
if (!gr.next) {  
   g_form.addErrorMessage('You must attach something');  
   return false;  
}

All fine and dandy (if you are fine with calling server side code in a client...yuck!)...But, of course, GlideRecord is NOT available in a scoped application client script! Adding global. doesn't fix it either. But wait, there is a workaround for this.. option 2a...

2a) Take the above script and move it to the 'global' application, then it works. The major downside is that this is NOT included in your application and won't promote properly. You'll have to install a global update set with the scoped app...this kinda breaks the whole idea of having a scoped app....so not a good solution, but it technically works...there has to be something better....

So how do we do it?

I love async calls and I love using script includes to handle server code. So I decided to always return false on the onSubmit. Then, in the ajax callback function, I submit the form again if the validation is successful. However, this is easier said than done...

First, g_form.submit() doesn't work on catalog items (too easy, darn it!). It'll give you an error saying use g_form.orderNow()...which doesn't work either!

Second, use good old DOM manipulation (even though SN doesn't recommend it) document.getElementById('submit_button').submit() ...oops, Scoped Apps don't allow access to the DOM! Thwarted again!

Now what? Well, it can be done, here's how:

1) Create a variable on your form called 'submitted', I just made it a single line text with '' by default. This will prevent recursion.

2) Hide that variable using a ui policy

3) Create your onSubmit client script, but instead of the normal ways mentioned above, get the HTMLElement and use .click()...

function onSubmit() {  
  if (g_form.getValue('submitted') == 'yes') // this prevents recursion  
    return true;  
  
  var ga = new GlideAjax('MyAttachmentUtils');  
  ga.addParam('sysparm_name', 'hasAttachment');  
  ga.addParam('sysparm_table', 'x_your_scoped_table_name');  
  ga.addParam('sysparm_id', g_form.getValue('sysparm_item_guid')); //don't use getUniqueValue, it's bogus if there is an attachment and this hasn't been submitted  
  ga.getXMLAnswer(function(response) {  
    g_form.clearMessages();  
    if (response == 'false')   
      g_form.addErrorMessage('You must attach a Statement of Work'); // no need to do anything else, false was already returned  
    else {  
      g_form.setValue('submitted', 'yes'); // set the hidden value to prevent recursion  
      if(g_form.getControl('submit_button')){
          g_form.getControl('submit_button').click(); // use HTMLElement to grab the button, then use click()  
       }else{
           g_form.submit();   //portal submit form
       }      
    }  
  });  
  
  return false;  
}