onSubmit client script runs when clicking “Click to add...” on a custom attachment/document field, b

[kishorvanam]

Hi everyone,

I have a custom table u_documentsdemo_table with a custom field u_document (type: [fill in: Document ID / Attachment / other, as shown in the dictionary entry]). On the form, this field shows a “Click to add...” link.

Requirement

I want to block the submit and show an alert (“Please attach the document before submitting”) if no document is attached, and allow the submit if a document is attached. I know a Mandatory field or UI Policy can do this, but I specifically need to implement it with an onSubmit client script for learning purposes.

What I built

An onSubmit client script (UI Type: All, Global checked, Isolate script checked) and a client-callable Script Include. Both are in the screenshots.

Client script:

function onSubmit() {
var ga = new GlideAjax('AttachmentCheck');
ga.addParam('sysparm_name', 'hasAttachment');
ga.addParam('sysparm_sys_id', g_form.getUniqueValue());
ga.getXMLWait();
var answer = ga.getAnswer();

if (answer == 'true') {
return true;
}
alert('Please attach the document before submitting.');
return false;
}

var AttachmentCheck = Class.create();
AttachmentCheck.prototype = Object.extendsObject(AbstractAjaxProcessor, {
hasAttachment: function() {
var recId = this.getParameter('sysparm_sys_id');
var gr = new GlideRecord('sys_attachment');
gr.addQuery('table_sys_id', recId);
gr.query();
if (gr.hasNext()) {
return 'true';
}
return 'false';
},
type: 'AttachmentCheck'
});

What works

• Clicking Submit with no attachment shows the alert and stops the submit.
• Adding a file with the paperclip icon at the top, then clicking Submit, saves the record.

What does not work

• When I click “Click to add...” on the u_document field, the alert “Please attach the document before submitting” appears immediately, and the file picker never opens. So I cannot add a file through the field at all. It behaves as if clicking the link triggers the onSubmit script.

What I already tried

• Filtering with g_form.getActionName() to skip non-submit actions. It did not change the behavior.
• Checking g_form.getValue('u_document') before calling GlideAjax. The alert still appears when the field is empty at click time.
• A UI Policy making u_document mandatory works as expected, but I need to understand and solve this with onSubmit.
• Action name shown when the link is clicked: [fill in, using a temporary script alert('Action name: ' + g_form.getActionName()); return true;, or write “no alert appeared”]
  
  
  

  My questions

  1. Why does clicking “Click to add...” on this field trigger the onSubmit script?
  2. How can I validate that a document is attached on Submit without blocking the field’s own “Click to add...” action?
  3. Is there a reliable way to tell a real Submit/Update click apart from the field’s internal action inside onSubmit?
  4. Does a file added through this field get stored in sys_attachment with a different table_name or table_sys_id than one added with the paperclip, especially on a new record that is not saved yet?
  
  
  
  

[vaishali231]

Hey @kishorvanam 

Could you please confirm the dictionary type of u_document? Is it a File Attachment field or a Document ID field?

[kishorvanam]

Hi  @vaishali231, thanks for replying. The dictionary type of u_document is File Attachment.

The issue: on a new record, when I click “Click to add...” on this field, my onSubmit script runs immediately and shows the alert before any file picker opens. The paperclip icon at the top works fine.

[Deėpak Sharma]

hi @kishorvanam 

1. Why does clicking "Click to add..." trigger the onSubmit script? Because you cannot attach a file to a record that doesn't exist yet. Attachments require a valid table_sys_id in the database. When you click "Click to add..." on a brand new record, the platform secretly forces a form submission (an insert) to create the record and generate a real sys_id so it has somewhere to attach the file. Your onSubmit script catches this forced save, sees that there is no attachment yet (because the upload window hasn't opened), and blocks the save. This breaks the link entirely.

How are files stored in sys_attachment for this field vs. the paperclip? (Your Question 4) This is a huge platform secret: files added via a specific File Attachment field do not use the standard table name. If your table is u_documentsdemo_table, files added via the paperclip get stored with table_name = u_documentsdemo_table. However, files added via your u_document field get stored with a special hidden prefix: table_name = ZZ_YYu_documentsdemo_table. This prefix is what tells the platform to hide that specific file from the global paperclip list at the top of the form and only display it inside your custom field.

using the standard Dictionary "Mandatory" checkbox is the only clean way to do this. ServiceNow's internal mandatory UI policies have hardcoded logic to bypass the block when you click "Click to add...", which custom onSubmit scripts don't have access to.

[kishorvanam]

Hi @Deėpak Sharma , thank you for the detailed explanation, that really helps.

I know a Mandatory field or UI Policy would solve this, but I specifically want to understand and solve it with a client script only for learning purposes.

One thing I don’t fully understand: on a new, unsaved record, the paperclip icon works fine without any save. I can add a file, and my onSubmit script is not triggered. As I understand it, the file is stored temporarily in sys_attachment using the sys_id the form already generated (with the ZZ_YY prefix), and it is linked properly when I click Submit.

So why does the “Click to add...” link on the File Attachment field need a forced insert, when the paperclip does not? Both are adding a file to a record that does not exist in the database yet.