Enable snippets to use reference filter cache

lib/banzai/filter/references/snippet_reference_filter.rb

@@ -11,10 +11,14 @@ module Banzai
         self.reference_type = :snippet
         self.object_class   = Snippet
 
-        def find_object(project, id)
+        def parent_records(project, ids)
           return unless project.is_a?(Project)
 
-          project.snippets.find_by(id: id)
+          project.snippets.where(id: ids.to_a)
+        end
+
+        def find_object(project, id)
+          reference_cache.records_per_parent[project][id]
         end
 
         def url_for_object(snippet, project)

spec/lib/banzai/filter/references/reference_cache_spec.rb

@@ -58,6 +58,7 @@ RSpec.describe Banzai::Filter::References::ReferenceCache do
       # Since this is an issue filter that is not batching issue queries
       # across projects, we have to account for that.
       # 1 for both projects, 1 for issues in each project == 3
+      # TODO: https://gitlab.com/gitlab-org/gitlab/-/issues/330359
       max_count = control_count + 1
 
       expect do

spec/lib/banzai/filter/references/snippet_reference_filter_spec.rb

@@ -219,4 +219,31 @@ RSpec.describe Banzai::Filter::References::SnippetReferenceFilter do
       expect(reference_filter(act, project: nil, group: create(:group)).to_html).to eq exp
     end
   end
+
+  context 'checking N+1' do
+    let(:namespace2) { create(:namespace) }
+    let(:project2)   { create(:project, :public, namespace: namespace2) }
+    let(:snippet2)   { create(:project_snippet, project: project2) }
+    let(:reference2) { "#{project2.full_path}$#{snippet2.id}" }
+
+    it 'does not have N+1 per multiple references per project', :use_sql_query_cache do
+      markdown = "#{reference} $9999990"
+
+      control_count = ActiveRecord::QueryRecorder.new(skip_cached: false) do
+        reference_filter(markdown)
+      end.count
+
+      markdown = "#{reference} $9999990 $9999991 $9999992 $9999993 #{reference2} something/cool$12"
+
+      # Since we're not batching snippet queries across projects,
+      # we have to account for that.
+      # 1 for both projects, 1 for snippets in each project == 3
+      # TODO: https://gitlab.com/gitlab-org/gitlab/-/issues/330359
+      max_count = control_count + 1
+
+      expect do
+        reference_filter(markdown)
+      end.not_to exceed_all_query_limit(max_count)
+    end
+  end
 end