Allow assigning users with private profiles

This matches the behavior of the UI.

Fixes: https://gitlab.com/gitlab-org/gitlab/-/issues/353331
Changelog: fixed

app/services/quick_actions/interpret_service.rb

@@ -79,7 +79,7 @@ module QuickActions
       # using a user-style reference, which is not in scope here.
       args        = params.split(/\s|,/).select(&:present?).uniq - ['and']
       usernames   = (args - ['me']).map { _1.delete_prefix('@') }
-      found       = User.by_username(usernames).to_a.select { can?(:read_user_profile, _1) }
+      found       = User.by_username(usernames).to_a.select { can?(:read_user, _1) }
       found_names = found.map(&:username).to_set
       missing     = args.reject { |arg| arg == 'me' || found_names.include?(arg.delete_prefix('@')) }.map { "'#{_1}'" }
 

spec/factories/users.rb

@@ -19,6 +19,10 @@ FactoryBot.define do
       public_email { email }
     end
 
+    trait :private_profile do
+      private_profile { true }
+    end
+
     trait :blocked do
       after(:build) { |user, _| user.block! }
     end

spec/services/quick_actions/interpret_service_spec.rb

@@ -682,6 +682,20 @@ RSpec.describe QuickActions::InterpretService do
 
         expect(message).to eq("Assigned #{developer.to_reference}.")
       end
+
+      context 'when the user has a private profile' do
+        let(:user) { create(:user, :private_profile) }
+        let(:content) { "/assign #{user.to_reference}" }
+
+        it 'assigns to the user' do
+          issuable.project.add_developer(user)
+
+          _, updates, message = service.execute(content, issuable)
+
+          expect(updates).to eq(assignee_ids: [user.id])
+          expect(message).to eq("Assigned #{user.to_reference}.")
+        end
+      end
     end
 
     shared_examples 'assign_reviewer command' do
@@ -971,24 +985,6 @@ RSpec.describe QuickActions::InterpretService do
         it_behaves_like 'assign_reviewer command'
       end
 
-      context 'with a private user' do
-        let(:ref) { create(:user, :unconfirmed).to_reference }
-        let(:content) { "/assign_reviewer #{ref}" }
-
-        it_behaves_like 'failed command', 'a parse error' do
-          let(:match_msg) { eq "Could not apply assign_reviewer command. Failed to find users for '#{ref}'." }
-        end
-      end
-
-      context 'with a private user, bare username' do
-        let(:ref) { create(:user, :unconfirmed).username }
-        let(:content) { "/assign_reviewer #{ref}" }
-
-        it_behaves_like 'failed command', 'a parse error' do
-          let(:match_msg) { eq "Could not apply assign_reviewer command. Failed to find users for '#{ref}'." }
-        end
-      end
-
       context 'with @all' do
         let(:content) { "/assign_reviewer @all" }