ContentDocumentLink Apex after insert trigger error

Question

Edit: I've built an after insert trigger on ContentDocumentLink. On cropredy's direction, I've bulkified my code and I think improved it generally. It "works" in that it accomplishes my business requirement, however my insert relies on a try-catch handler that I should learn how to do without.

The goal: whenever someone creates a ContentNote or attaches a File (a ContentDocument), I want to automatically share it with a Chatter group that I created, called ContentNote Administration. This ensures we'll have back-end visibility on all notes and files.

Here are the steps I want my code to execute:

1. When someone creates a new Document (like a File upload or a ContentNote), Salesforce inserts a record into ContentDocumentLink, relating that record (say, ContentNote) with the owner. Then, I want the trigger to fire.
2. The trigger passes the ContentDocumentLink sObject, along with the name of the link-to object type and name (in this case, a CollaborationGroup named 'ContentNote Administration').
3. If a ContentDocumentLink record already exists relating this ContentDocumentId with this LinkedEntityId, don't insert.
4. If the current insert relates this ContentDocumentId with this LinkedEntityId, don't insert - I believe this is necessary to avoid infinite loop.
5. Else, build a new ContentDocumentLink record and insert it.

Here is my trigger:

trigger vwContentDocumentLinkAction on ContentDocumentLink (before delete, before insert, before update, after delete, after insert, after update) {

    if (Trigger.isAfter) {

        if (Trigger.isInsert) {

            List<ContentDocumentLink> cdLinks = new List<ContentDocumentLink>();

            SObject cGID = [SELECT Id FROM CollaborationGroup WHERE Name = 'ContentNote Administration' LIMIT 1];

                for (ContentDocumentLink cdl : Trigger.new) {
                    if(vwContentNoteVisible.shouldShare(cdl, cGID)) { // don't add if it's a recursive trigger
                        cdLinks.add(cdl);
                    }
                }

            vwContentNoteVisible.shareWithCollaborationGroup(cdLinks, cGID);

        }
    }
}

Here is my class:

public class vwContentNoteVisible {

    public static void shareWithCollaborationGroup(List<ContentDocumentLink> cdlNeedLinks, SObject collabGroup) {

        for (ContentDocumentLink cdl : cdlNeedLinks) {
            ContentDocumentLink cdlNewLink = new ContentDocumentLink();

            cdlNewLink.ContentDocumentId = cdl.ContentDocumentId;
            cdlNewLink.LinkedEntityId = collabGroup.Id;
            cdlNewLink.ShareType = 'V';
            cdlNewLink.Visibility = 'AllUsers';

            // exception handler: catches DML Field_Integrity_Exception on recursion trigger
            // This is because ContentDocumentLink doesn't permit duplicates.
            try {

                insert(cdlNewLink);

            } catch(DmlException e) { System.debug('Exception occurred on insert: ' + e.getMessage()); }
            // do without this try catch, once you build your set of DocumentIDs
        }
    }

    public static Boolean shouldShare(ContentDocumentLink thisLink, SObject collabGroup) {

        if(thisLink.LinkedEntityId == collabGroup.Id) {
            return false;
        } else {
            return true;
        }
    }
}

My try-catch handles the following Field Integrity Exception that results because the insert recursively calls this trigger:

caused by: System.DmlException: Insert failed. First exception on row 0; >first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, >vwContentDocumentLink_sharing: execution of AfterInsert

caused by: System.DmlException: Insert failed. First exception on row 0; >first error: FIELD_INTEGRITY_EXCEPTION, Document with ID: >0690j0000008nkf is already linked with the entity with ID: >0F90j0000008T0T: Linked Entity ID: [LinkedEntityId]

What are the best strategies for handling this recursive insert without relying on error handling? Any help would be appreciated.

Answer 1

while researching a problem similar to yours, I found an answer you might find useful:

Document already Linked

Basically the idea is to introduce a check on whether there is an existing ContentDocumentLink with the same LinkedEntityId before inserting. However, the check avoids the error but prevents insertion, which is after all not that different from your try / catch block. I still haven't found a solution to avoid the error AND insert the record. I'll keep you posted if I find it.