FIX: Don't attempt to add user again to a group when syncing groups via SSO (#18772)

This commit fixes a regression introduced in 8979adc where under certain conditions the groups syncing logic in Discourse Connect would try to add users to groups they're already members of and cause errors when users try to sign in using Discourse Connect.

app/models/discourse_connect.rb

@@ -187,15 +187,17 @@ class DiscourseConnect < DiscourseConnectBase
   def synchronize_groups(user)
     names = (groups || "").split(",").map(&:downcase)
 
-    to_be_added = Group.where('LOWER(NAME) in (?) AND NOT automatic', names)
-    to_be_removed = Group.joins(:group_users).where(automatic: false, group_users: { user_id: user.id })
+    current_groups = user.groups.where(automatic: false)
+    desired_groups = Group.where('LOWER(NAME) in (?) AND NOT automatic', names)
 
-    if to_be_added.present?
-      to_be_removed = to_be_removed.where("groups.id NOT IN (?)", to_be_added.map(&:id)).to_a
+    to_be_added = desired_groups
+    if current_groups.present?
+      to_be_added = to_be_added.where("groups.id NOT IN (?)", current_groups.map(&:id))
     end
 
-    if to_be_removed.present?
-      to_be_added = to_be_added.where("groups.id NOT IN (?)", to_be_removed.map(&:id)).to_a
+    to_be_removed = current_groups
+    if desired_groups.present?
+      to_be_removed = to_be_removed.where("groups.id NOT IN (?)", desired_groups.map(&:id))
     end
 
     if to_be_added.present? || to_be_removed.present?
@@ -406,12 +408,8 @@ class DiscourseConnect < DiscourseConnectBase
 
   def add_user_to_groups(user, groups)
     groups.each do |group|
-      begin
-        GroupUser.create!(user_id: user.id, group_id: group.id)
-        GroupActionLogger.new(Discourse.system_user, group).log_add_user_to_group(user)
-      rescue Exception => e
-        Discourse.warn_exception(e, message: "User already in group")
-      end
+      GroupUser.create!(user_id: user.id, group_id: group.id)
+      GroupActionLogger.new(Discourse.system_user, group).log_add_user_to_group(user)
     end
   end
 

spec/models/discourse_connect_spec.rb

@@ -206,7 +206,7 @@ RSpec.describe DiscourseConnect do
     expect(group2.usernames).to eq("")
 
     group1.add(user)
-    group1.save
+    group1.save!
 
     sso.lookup_or_create_user(ip_address)
     expect(group1.usernames).to eq("")
@@ -216,6 +216,16 @@ RSpec.describe DiscourseConnect do
     sso.lookup_or_create_user(ip_address)
     expect(group1.usernames).to eq("")
     expect(group2.usernames).to eq("")
+
+    group1.add(user)
+    group1.save!
+    group2.add(user)
+    group2.save!
+    sso.groups = "#{group1.name},badname,trust_level_4"
+
+    sso.lookup_or_create_user(ip_address)
+    expect(group1.usernames).to eq(user.username)
+    expect(group2.usernames).to eq("")
   end
 
   it "can specify groups" do