FIX: Use polymorphic bookmarks for in:bookmarks search (#16684)

This commit makes sure the in:bookmarks post advanced
search filter works with polymorphic bookmarks.

lib/search.rb

@@ -453,13 +453,24 @@ class Search
     end
   end
 
-  # TODO (martin) [POLYBOOK] Make a separate PR for advanced searched in:bookmarks
-  # functionality as the bookmarkables will have to define this.
+  # NOTE: With polymorphic bookmarks it may make sense to possibly expand
+  # this at some point, as it only acts on posts at the moment. On the other
+  # hand, this may not be necessary, as the user bookmark list has advanced
+  # search based on a RegisteredBookmarkable's #search_query method.
   advanced_filter(/^in:(bookmarks)$/i) do |posts, match|
     if @guardian.user
+      if SiteSetting.use_polymorphic_bookmarks
+        posts.where(<<~SQL)
+          posts.id IN (
+            SELECT bookmarkable_id FROM bookmarks
+            WHERE bookmarks.user_id = #{@guardian.user.id} AND bookmarks.bookmarkable_type = 'Post'
+          )
+        SQL
+      else
         posts.where("posts.id IN (SELECT post_id FROM bookmarks WHERE bookmarks.user_id = #{@guardian.user.id})")
       end
     end
+  end
 
   advanced_filter(/^in:posted$/i) do |posts|
     posts.where("posts.user_id = #{@guardian.user.id}") if @guardian.user

spec/lib/search_spec.rb

@@ -1471,6 +1471,34 @@ describe Search do
   end
 
   describe 'Advanced search' do
+    describe "bookmarks" do
+      fab!(:user) { Fabricate(:user) }
+      let!(:bookmark_post1) { Fabricate(:post, raw: 'boom this is a bookmarked post') }
+      let!(:bookmark_post2) { Fabricate(:post, raw: 'wow some other cool thing') }
+
+      def search_with_bookmarks
+        Search.execute('boom in:bookmarks', guardian: Guardian.new(user))
+      end
+
+      it "can filter by posts in the user's bookmarks" do
+        expect(search_with_bookmarks.posts.map(&:id)).to eq([])
+        Fabricate(:bookmark, user: user, post: bookmark_post1)
+        expect(search_with_bookmarks.posts.map(&:id)).to match_array([bookmark_post1.id])
+      end
+
+      context "using polymorphic bookmarks" do
+        before do
+          SiteSetting.use_polymorphic_bookmarks = true
+        end
+
+        it "can filter by posts in the user's bookmarks" do
+          expect(search_with_bookmarks.posts.map(&:id)).to eq([])
+          bm = Fabricate(:bookmark, user: user, bookmarkable: bookmark_post1)
+          expect(search_with_bookmarks.posts.map(&:id)).to match_array([bookmark_post1.id])
+        end
+      end
+    end
+
     it 'supports pinned' do
       Fabricate(:post, raw: 'hi this is a test 123 123', topic: topic)
       _post = Fabricate(:post, raw: 'boom boom shake the room', topic: topic)