How to customize / override topic guardian through a plugin

Haider · February 15, 2021, 3:30am

I am getting a plugin developed that will add a boolean value based on some custom logic to the user_custom_fields table for each user who is not allowed to create a new topic.

user.custom_fields['can_create_topic'] = false;

What I want to do?
I want to hide the “+ New Topic” button for some users based on custom logic.

Question
Is it possible to customize can_create_topic? guardian so that it performs an additional check on a user_custom_field to determine if a user is allowed to create a new topic or not?

neounix · February 15, 2021, 9:50am

Yes, of course you can modify Ruby classes with plugins. It’s software, easily modified, not intergalactic space travel using solar sails or worm-holes, so of course it’s possible to modify Discourse behavior with a plugin:

github.com

discourse/discourse/blob/master/lib/guardian.rb

# frozen_string_literal: true

require 'guardian/category_guardian'
require 'guardian/ensure_magic'
require 'guardian/post_guardian'
require 'guardian/bookmark_guardian'
require 'guardian/topic_guardian'
require 'guardian/user_guardian'
require 'guardian/post_revision_guardian'
require 'guardian/group_guardian'
require 'guardian/tag_guardian'

# The guardian is responsible for confirming access to various site resources and operations
class Guardian
  include EnsureMagic
  include CategoryGuardian
  include PostGuardian
  include BookmarkGuardian
  include TopicGuardian
  include UserGuardian

This file has been truncated. show original

pfaffman · February 15, 2021, 12:55pm

I don’t know your use case, but the easy and safe way to do that would be to add or remove those users from a group with the permission to create a topic.

Haider · February 15, 2021, 2:59pm

@pfaffman That is a good idea too. But I think if I can override the can_create_topic? method in the TopicGuardian that would be a cleaner solution. Is there any plugin I can refer to that has a similar change?

What I don’t know is how can I make my TopicGuardian subclass from the plugin to replace TopicGuardian in the Guardian class because it is being mixed in rather than dependency injected.

Haider · February 15, 2021, 10:00pm

Okay. I think I found my answer. I just have to implement the “can_create_topic?” method in module ::TopicGuardian and it will automatically change TopicGuardian’s behavior without requiring to inject or registering it somewhere. Also, I can use super method inside my override method so that I don’t have to always manually keep it in sync with the original method in case that gets changed.

Got help from this topic: Overriding user_guardian.rb in a plugin (no fork necessary!)