Prevent ontology term links being recreated on every update. Fixes #1270

lib/has_ontology_terms.rb

@@ -47,6 +47,26 @@ def has_ontology_terms(association_name, ontology: Edam::Ontology.instance, bran
       self.ontology_term_fields ||= []
       self.ontology_term_fields << method.to_sym
 
+      define_method "#{links_method}=" do |links|
+        send(links_method).reset
+        current_links = send(links_method).to_a
+        to_keep = []
+
+        links.reject(&:blank?).map do |link|
+          idx = current_links.index { |l| l.term_uri == link.term_uri }
+          if idx
+            match = current_links.delete_at(idx)
+            to_keep << match
+          else
+            to_keep << link
+          end
+        end
+
+        current_links.each(&:mark_for_destruction) # Now contains only redundant records
+
+        super(to_keep)
+      end
+
       # OntologyTerm objects
       define_method method do
         send(links_method).map(&:ontology_term).uniq

test/models/event_test.rb

@@ -775,4 +775,33 @@ class EventTest < ActiveSupport::TestCase
     assert_equal 'Goblet', bioschemas[:provider].first['name']
     assert_equal 'http://mygoblet.org', bioschemas[:provider].first['url']
   end
+
+  test 'does not destroy and recreate ontology term links' do
+    e = events(:scraper_user_event)
+
+    # Via names
+    assert_difference('OntologyTermLink.count', 2) do
+      e.scientific_topic_names = %w[Proteins Chromosomes]
+      e.save!
+      assert_equal 2, e.scientific_topics.count
+    end
+
+    ontology_term_links = e.ontology_term_links.to_a
+
+    assert_no_difference('OntologyTermLink.count') do
+      e.scientific_topic_names = %w[Proteins Chromosomes]
+      e.save!
+      assert_equal 2, e.scientific_topics.count
+    end
+
+    assert_equal ontology_term_links, e.reload.ontology_term_links.to_a
+
+    assert_no_difference('OntologyTermLink.count') do
+      e.scientific_topic_names = %w[Proteins Biodiversity]
+      e.save!
+      assert_equal 2, e.scientific_topics.count
+    end
+
+    assert_equal 1, (e.reload.ontology_term_links.to_a - ontology_term_links).length
+  end
 end