Banzai - avoid redis if attr is in DB cachebanzai-avoid-redis-if-db-cache

When cache_collection_render runs we end up reading and writing
things to redis even if we already have the rendered field cached
in the DB. This commit avoids using redis at all whenever we have
the field already rendered in the DB cache.

2 files changed, 22 insertions, 3 deletions

diff --git a/spec/lib/banzai/renderer_spec.rb b/spec/lib/banzai/renderer_spec.rb
index aa828e2f0e9..a099f7482c1 100644
--- a/spec/lib/banzai/renderer_spec.rb
+++ b/spec/lib/banzai/renderer_spec.rb
@@ -19,6 +19,24 @@ describe Banzai::Renderer do
     object
   end
 
+  describe '#cache_collection_render' do
+    let(:merge_request) { fake_object(fresh: true) }
+    let(:context) { { cache_key: [merge_request, 'field'], rendered: merge_request.field_html } }
+
+    context 'when an item has a rendered field' do
+      before do
+        allow(merge_request).to receive(:field).and_return('This is the field')
+        allow(merge_request).to receive(:field_html).and_return('This is the field')
+      end
+
+      it 'does not touch redis if the field is in the cache' do
+        expect(Rails).not_to receive(:cache)
+
+        described_class.cache_collection_render([{ text: merge_request.field, context: context }])
+      end
+    end
+  end
+
   describe '#render_field' do
     let(:renderer) { described_class }
 
diff --git a/spec/lib/gitlab/markdown_cache/active_record/extension_spec.rb b/spec/lib/gitlab/markdown_cache/active_record/extension_spec.rb
index 18052b1991c..c5fc74afea5 100644
--- a/spec/lib/gitlab/markdown_cache/active_record/extension_spec.rb
+++ b/spec/lib/gitlab/markdown_cache/active_record/extension_spec.rb
@@ -9,12 +9,13 @@ describe Gitlab::MarkdownCache::ActiveRecord::Extension do
       cache_markdown_field :title, whitelisted: true
       cache_markdown_field :description, pipeline: :single_line
 
-      attr_accessor :author, :project
+      attribute :author
+      attribute :project
     end
   end
 
   let(:cache_version) { Gitlab::MarkdownCache::CACHE_COMMONMARK_VERSION << 16 }
-  let(:thing) { klass.new(title: markdown, title_html: html, cached_markdown_version: cache_version) }
+  let(:thing) { klass.create(title: markdown, title_html: html, cached_markdown_version: cache_version) }
 
   let(:markdown) { '`Foo`' }
   let(:html) { '<p data-sourcepos="1:1-1:5" dir="auto"><code>Foo</code></p>' }
@@ -37,7 +38,7 @@ describe Gitlab::MarkdownCache::ActiveRecord::Extension do
   end
 
   context 'a changed markdown field' do
-    let(:thing) { klass.new(title: markdown, title_html: html, cached_markdown_version: cache_version) }
+    let(:thing) { klass.create(title: markdown, title_html: html, cached_markdown_version: cache_version) }
 
     before do
       thing.title = updated_markdown