From d880db3b7b748901366d0c94f58dada9096f967f Mon Sep 17 00:00:00 2001
From: Mark VanLandingham <markvanlan@gmail.com>
Date: Fri, 22 Nov 2024 14:49:39 -0600
Subject: [PATCH] DEV: Apply modifier for topic_view link_counts (#29883)

---
 lib/topic_view.rb           | 10 +++++++-
 spec/lib/topic_view_spec.rb | 51 ++++++++++++++++++++++++++-----------
 2 files changed, 45 insertions(+), 16 deletions(-)

diff --git a/lib/topic_view.rb b/lib/topic_view.rb
index 16aed2f74f7..f7e4745997d 100644
--- a/lib/topic_view.rb
+++ b/lib/topic_view.rb
@@ -684,7 +684,15 @@ class TopicView
   end
 
   def link_counts
-    @link_counts ||= TopicLink.counts_for(@guardian, @topic, posts)
+    # Normal memoizations doesn't work in nil cases, so using the ol' `defined?` trick
+    # to memoize more safely, as a modifier could nil this out.
+    return @link_counts if defined?(@link_counts)
+
+    @link_counts =
+      DiscoursePluginRegistry.apply_modifier(
+        :topic_view_link_counts,
+        TopicLink.counts_for(@guardian, @topic, posts),
+      )
   end
 
   def pm_params
diff --git a/spec/lib/topic_view_spec.rb b/spec/lib/topic_view_spec.rb
index b4789fb92d8..dfb49f39b30 100644
--- a/spec/lib/topic_view_spec.rb
+++ b/spec/lib/topic_view_spec.rb
@@ -1123,29 +1123,50 @@ RSpec.describe TopicView do
     end
   end
 
-  describe "with topic_view_suggested_topics_options modifier" do
-    let!(:topic1) { Fabricate(:topic) }
-    let!(:topic2) { Fabricate(:topic) }
+  describe "plugin modifiers" do
+    let(:plugin) { Plugin::Instance.new }
 
-    after { DiscoursePluginRegistry.clear_modifiers! }
+    context "with topic_view_link_counts modifier registered" do
+      let(:modifier) do
+        Proc.new do |link_counts|
+          link_counts["hijacked hehe"] = true
+          link_counts
+        end
+      end
 
-    it "allows disabling of random suggested" do
-      topic_view = TopicView.new(topic1)
+      it "allows modifications to link_counts" do
+        expect(TopicView.new(topic).link_counts).to eq({})
 
-      Plugin::Instance
-        .new
-        .register_modifier(
-          :topic_view_suggested_topics_options,
-        ) do |suggested_options, inner_topic_view|
-          expect(inner_topic_view).to eq(topic_view)
+        plugin.register_modifier(:topic_view_link_counts, &modifier)
+
+        expect(TopicView.new(topic).link_counts).to eq({ "hijacked hehe" => true })
+      ensure
+        DiscoursePluginRegistry.unregister_modifier(plugin, :topic_view_link_counts, &modifier)
+      end
+    end
+
+    context "with topic_view_suggested_topics_options modifier" do
+      let!(:topic1) { Fabricate(:topic) }
+      let!(:topic2) { Fabricate(:topic) }
+      let(:modifier) do
+        Proc.new do |suggested_options, inner_topic_view|
           suggested_options.merge(include_random: false)
         end
+      end
 
-      expect(topic_view.suggested_topics.topics.count).to eq(0)
+      it "allows modifications to suggested topics (disabling of random suggested)" do
+        expect(TopicView.new(topic1).suggested_topics.topics.count).to be > 0
 
-      DiscoursePluginRegistry.clear_modifiers!
+        plugin.register_modifier(:topic_view_suggested_topics_options, &modifier)
 
-      expect(TopicView.new(topic1).suggested_topics.topics.count).to be > 0
+        expect(TopicView.new(topic1).suggested_topics.topics.count).to eq(0)
+      ensure
+        DiscoursePluginRegistry.unregister_modifier(
+          plugin,
+          :topic_view_suggested_topics_options,
+          &modifier
+        )
+      end
     end
   end
 end