FIX: Don't fail because flair_uploads weren't eager loaded (#379)

The basic group serializer complains that the flair_upload relation has to be eager loaded when attempting to included assigned groups in search results, which is a consequence of using strict loading during search's preload to
avoid N+1.

Eager loading the association during this would definitely fix the problem, but is it the right solution? It seems to me that this serializer does too much, when we only need a small number of attributes to display the assigned
widget. Instead, this commit adds a lightweight custom serializer which grabs only the essentials for it to work.

app/serializers/assigned_group_serializer.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class AssignedGroupSerializer < ApplicationSerializer
+  attributes :id, :name, :assign_icon, :assign_path
+
+  def assign_icon
+    "group-plus"
+  end
+
+  def assign_path
+    "/g/#{object.name}/assigned/everyone"
+  end
+end

plugin.rb

@@ -624,7 +624,7 @@ after_initialize do
   end
 
   add_to_serializer(:topic_list_item, :assigned_to_group) do
-    BasicGroupSerializer.new(object.assigned_to, scope: scope, root: false).as_json
+    AssignedGroupSerializer.new(object.assigned_to, scope: scope, root: false).as_json
   end
 
   add_to_serializer(:topic_list_item, :include_assigned_to_group?) do
@@ -648,7 +648,7 @@ after_initialize do
   end
 
   add_to_serializer(:search_topic_list_item, :assigned_to_group, false) do
-    BasicGroupSerializer.new(object.assigned_to, scope: scope, root: false).as_json
+    AssignedGroupSerializer.new(object.assigned_to, scope: scope, root: false).as_json
   end
 
   add_to_serializer(:search_topic_list_item, "include_assigned_to_group?") do
@@ -700,7 +700,7 @@ after_initialize do
 
   add_to_serializer(:user_bookmark_base, :assigned_to_group, false) do
     return if !can_have_assignment?
-    BasicGroupSerializer.new(assigned_to, scope: scope, root: false).as_json
+    AssignedGroupSerializer.new(assigned_to, scope: scope, root: false).as_json
   end
 
   add_to_serializer(:user_bookmark_base, "include_assigned_to_group?") do
@@ -714,10 +714,6 @@ after_initialize do
     SiteSetting.assigns_user_url_path.gsub("{username}", object.username)
   end
 
-  add_to_serializer(:basic_group, :assign_icon) { "group-plus" }
-
-  add_to_serializer(:basic_group, :assign_path) { "/g/#{object.name}/assigned/everyone" }
-
   # PostSerializer
   add_to_serializer(:post, :assigned_to_user) do
     BasicUserSerializer.new(object.assignment.assigned_to, scope: scope, root: false).as_json
@@ -729,7 +725,7 @@ after_initialize do
   end
 
   add_to_serializer(:post, :assigned_to_group, false) do
-    BasicGroupSerializer.new(object.assignment.assigned_to, scope: scope, root: false).as_json
+    AssignedGroupSerializer.new(object.assignment.assigned_to, scope: scope, root: false).as_json
   end
 
   add_to_serializer(:post, "include_assigned_to_group?") do

spec/requests/search_controller_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+describe SearchController do
+  fab!(:admin) { Fabricate(:admin) }
+  fab!(:group) do
+    Fabricate(
+      :group,
+      assignable_level: Group::ALIAS_LEVELS[:everyone],
+      flair_upload: Fabricate(:upload),
+    )
+  end
+
+  before do
+    SiteSetting.assign_enabled = true
+    sign_in(admin)
+  end
+
+  after { Discourse.redis.flushdb }
+
+  it "include assigned group in search result" do
+    SearchIndexer.enable
+    SiteSetting.use_pg_headlines_for_excerpt = true
+
+    post = Fabricate(:post, topic: Fabricate(:topic, title: "this is an awesome title"))
+
+    Assigner.new(post.topic, admin).assign(group)
+
+    get "/search/query.json", params: { term: "awesome" }
+
+    expect(response.status).to eq(200)
+    assigned_to_group_data = response.parsed_body["topics"][0]["assigned_to_group"]
+
+    expect(assigned_to_group_data["id"]).to eq(group.id)
+    expect(assigned_to_group_data["name"]).to eq(group.name)
+    expect(assigned_to_group_data["assign_icon"]).to eq("group-plus")
+    expect(assigned_to_group_data["assign_path"]).to eq("/g/#{group.name}/assigned/everyone")
+  end
+end