Check the discussion lock only for issuables & clean style

app/controllers/projects/notes_controller.rb

@@ -77,7 +77,7 @@ class Projects::NotesController < Projects::ApplicationController
   def authorize_create_note!
     noteable_type = note_params[:noteable_type]
-    return unless ['MergeRequest', 'Issue'].include?(noteable_type)
+    return unless %w[MergeRequest Issue].include?(noteable_type)
     return access_denied! unless can?(current_user, :create_note, project)
     noteable = noteable_type.constantize.find(note_params[:noteable_id])

app/policies/note_policy.rb

@@ -7,7 +7,7 @@ class NotePolicy < BasePolicy
   condition(:is_noteable_author) { @user && @subject.noteable.author_id == @user.id }
   condition(:editable, scope: :subject) { @subject.editable? }
-  condition(:locked) { @subject.noteable.discussion_locked? }
+  condition(:locked) { [MergeRequest, Issue].include?(@subject.noteable.class) && @subject.noteable.discussion_locked? }
   rule { ~editable | anonymous }.prevent :edit_note

spec/controllers/projects/notes_controller_spec.rb

@@ -253,7 +253,7 @@ describe Projects::NotesController do
         end
         it 'creates a new note' do
-          expect{ post :create, request_params }.to change { Note.count }.by(1)
+          expect { post :create, request_params }.to change { Note.count }.by(1)
         end
       end
@@ -269,7 +269,7 @@ describe Projects::NotesController do
         end
         it 'does not create a new note' do
-          expect{ post :create, request_params }.not_to change { Note.count }
+          expect { post :create, request_params }.not_to change { Note.count }
         end
       end
     end