AI: address review on PR #464

backend/app/controllers/tag_versions_controller.rb

@@ -69,8 +69,11 @@ class TagVersionsController < ApplicationController
 
       parent_tags =
           build_version_values(cur_parent_tag_ids, prev_parent_tag_ids, key: :tag_id)
-          .map do |h|
-            { tag: parent_json.fetch(h[:tag_id]),
+          .filter_map do |h|
+            parent = parent_json[h[:tag_id]]
+            next unless parent
+
+            { tag: parent,
               type: h[:type] }
           end
 

backend/spec/requests/tag_versions_spec.rb

@@ -215,6 +215,36 @@ RSpec.describe 'TagVersions API', type: :request do
       expect(first.fetch('created_at')).to eq(t_v1.iso8601)
     end
 
+    [:parent_shared, :parent_new, :parent_old].each do |parent_key|
+      it "omits deleted #{ parent_key } from parent diffs" do
+        deleted_parent = public_send(parent_key)
+        deleted_parent.tag_names.destroy_all
+        deleted_parent.destroy!
+
+        get '/tags/versions', params: { id: tag.id }
+
+        expect(response).to have_http_status(:ok)
+        expect(json.fetch('count')).to eq(2)
+
+        versions = json.fetch('versions')
+        expect(versions.map { _1.fetch('version_no') }).to eq([2, 1])
+
+        expected_parents = [
+            [parent_shared.id, 'context'],
+            [parent_new.id, 'added'],
+            [parent_old.id, 'removed']].reject { _1.first == deleted_parent.id }
+        expect(versions.first.fetch('parent_tags').map { |entry|
+          [entry.fetch('tag').fetch('id'), entry.fetch('type')]
+        }).to eq(expected_parents)
+
+        expected_first_parents = [parent_shared.id, parent_old.id]
+            .reject { _1 == deleted_parent.id }.map { [_1, 'added'] }
+        expect(versions.second.fetch('parent_tags').map { |entry|
+          [entry.fetch('tag').fetch('id'), entry.fetch('type')]
+        }).to eq(expected_first_parents)
+      end
+    end
+
     it 'returns empty when the specified tag has no versions' do
       fresh_tag = create(:tag, primary_name: 'no_versions_tag', category: :general)