DEV: Fix tags filter with more than 2 tag names in value not working (#21380)

Specifying more than two tag names when using the `tag:` filter was not
working because of a bug in the code where only the first two value in
the `tag:` filter was being selected.

lib/topics_filter.rb

@@ -309,6 +309,7 @@ class TopicsFilter
         .filter_visible(Tag, @guardian)
         .where_name(tag_names)
         .pluck(:id, :target_tag_id)
+        .transpose
 
     tag_ids ||= []
     alias_tag_ids ||= []
@@ -417,7 +418,7 @@ class TopicsFilter
 
   def include_topics_with_all_tags(tag_ids)
     tag_ids.each do |tag_id|
-      sql_alias = "tt#{topic_tags_alias}"
+      sql_alias = topic_tags_alias
 
       @scope =
         @scope.joins(
@@ -427,7 +428,13 @@ class TopicsFilter
   end
 
   def include_topics_with_any_tags(tag_ids)
-    @scope = @scope.joins(:topic_tags).where("topic_tags.tag_id IN (?)", tag_ids).distinct(:id)
+    sql_alias = topic_tags_alias
+
+    @scope =
+      @scope
+        .joins("INNER JOIN topic_tags #{sql_alias} ON #{sql_alias}.topic_id = topics.id")
+        .where("#{sql_alias}.tag_id IN (?)", tag_ids)
+        .distinct(:id)
   end
 
   ORDER_BY_MAPPINGS = {

spec/lib/topics_filter_spec.rb

@@ -694,6 +694,37 @@ RSpec.describe TopicsFilter do
         ).to contain_exactly(topic_with_tag_and_tag2.id, topic_with_tag_and_tag2_and_tag3.id)
       end
 
+      describe "when query string is `tags:tag1,tag2,tag3`" do
+        it "should only return topics that are tagged with either tag1, tag2 or tag3" do
+          topic_with_tag3 = Fabricate(:topic, tags: [tag3])
+
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("tags:#{tag.name},#{tag2.name},#{tag3.name}")
+              .pluck(:id),
+          ).to contain_exactly(
+            topic_with_tag.id,
+            topic_with_tag_and_tag2.id,
+            topic_with_tag2.id,
+            topic_with_tag3.id,
+          )
+        end
+      end
+
+      describe "when query string is `tags:tag1+tag2+tag3`" do
+        it "should only return topics that are tagged with tag1, tag2 and tag3" do
+          topic_with_tag_tag2_tag3 = Fabricate(:topic, tags: [tag, tag2, tag3])
+
+          expect(
+            TopicsFilter
+              .new(guardian: Guardian.new)
+              .filter_from_query_string("tags:#{tag.name}+#{tag2.name}+#{tag3.name}")
+              .pluck(:id),
+          ).to contain_exactly(topic_with_tag_tag2_tag3.id)
+        end
+      end
+
       it "should only return topics that are tagged with tag1 and tag2 but not tag3 when query string is `tags:tag1 tags:tag2 -tags:tag3`" do
         topic_with_tag_and_tag2_and_tag3 = Fabricate(:topic, tags: [tag, tag2, tag3])